Best Gear Oil For Ford 9 Inch? Quick Answer

Synthetic lubricants continue to gain market share thanks to better performance characteristics that trump higher drum costs in many applications. Demand in the United States has increased to $2.2 billion per year due to tighter environmental and occupational safety requirements.

Almost all customers regularly take up the “mineral oil vs. synthetic lubricants” discussion. In certain situations it is part of an overall requirements plan; In other cases, it is simply a matter of ensuring that the asset receives the best life cycle value.

Acculube facilitates this process, helping customers complete the math based on their specific situation to find the best program for their needs. Processes and products change, and the price volatility of crude oil at the producer level significantly affects the equation; it is therefore worth taking a fresh look at least once a year.

mineral oils

Many factors distinguish mineral oils from synthetic lubricants, including their performance, their requirements for efficient functionality, and their composition.

Naturally occurring crude oil is a cocktail of hydrocarbons. Even after aggressive solvent-based refining, thousands of hydrocarbon compounds as well as organic compounds of oxygen, sulfur and nitrogen remain.

These three compounds in particular are problematic as they allow for oxidation, acid evolution and promote sludge formation, particularly in high temperature applications.

The different molecules of refined lubricants also have different shapes, resulting in irregular lubricant surfaces at the molecular level. These irregularities create friction within the fluid itself, increasing power requirements and reducing efficiency.

synthetic

In contrast, synthetic lubricants are engineered products created through chemical reactions through the precise application of pressure and temperature to a specific recipe of components. All components are highly pure with strong molecular bonds.

As a result, the end product is a pure compound, less prone to oxidation, highly resistant to degradation, and of uniform molecular size. This molecular size uniformity prevents plastics from gelling when cold (they contain no waxes), and their specific molecular structure prevents them from thinning when heated; therefore the protective properties of the lubricant are more predictable.

The saturated molecules created by the synthesis process are also not hydrophilic and will not emulsify in high humidity environments or produce unwanted by-products.

traction coefficient

Molecular size is also key to one of the operational virtues of synthetic lubricants – their coefficient of traction or internal fluid friction (drag). The traction coefficient is the shear or tangential force required to move a load divided by the load. The coefficient number expresses how easily the lubricating film is sheared off.

Compared to mineral oil molecules, for example, synthetic lubricants have up to a 30 percent advantage over mineral oils in traction coefficient. This means the force required to move a load is less, meaning less horsepower is required to get the job done.

In a gear reducer, the lubricant is sheared in gear meshing, and the lower the traction coefficient, the less energy is dissipated by shearing the lubricant. The difference is realized through a low power consumption of the motor and a reduced lubricant/gearbox temperature.

Switching to a low-traction plastic reduces power consumption in a spur/helical gear by 0.5 percent per reduction and by up to 8 percent in high-reduction worm gears.

gear wear

The problem of gear wear is also taken into account. A study cited in the journal Machinery Lubrication1 states that synthetic lubricants make gears more efficient than mineral oils. A polyglycol showed the highest efficiency (18 percent more than the high-performing mineral oil).

Synthetic hydrocarbon gear oils (SHC) also increased the efficiency of the best gears by eight to nine percent. The performance of synthetic lubricants in USDA-H1 food contact applications is also beneficial. It is sometimes assumed that food-grade plastics are inferior in performance to mineral oil lubricants, an assumption that the study refutes.

lifespan

A popular topic regarding the difference between mineral oils and synthetic lubricants is service life. Synthetic lubricants as a class do not age, especially at high temperatures, and have a longer service life.

In the case of plastics, the change interval is often many times longer at the same operating temperatures; However, the exact number depends on operating conditions, additives and the specific plastic used.

Synthetic lubricants have a lower coefficient of friction in a gear, better film strength, and a better viscosity-temperature relationship (Viscosity Index, VI). This indicates that synthetic lubricants can be used at lower viscosity levels and lower temperatures. When this is the case, the gap between the lifespans of minerals and plastics increases significantly.

Related to the oil change interval is the issue of product loss through evaporation and disposal. Both sludge and residue form more easily with petroleum products. Evaporative losses are lower in plastics due to the lack of lighter hydrocarbon structures.

Disposal of some plastics is more expensive, but by far not enough to compensate for the three to five times more frequent change intervals.

security

In terms of safety and insurance risks, the flash point for plastics is consistently higher as a class, and reduced flammability is a key driver of the growing popularity of plastics in high-temperature applications.

Disadvantages

Like most other lubricants, plastics can have disadvantages. Material compatibility issues may arise with certain seals, metals, paints, coatings and plastics. Many ester-type plastics do not work well in the presence of water and can decompose or decompose (hydrolysis). They can also cost more per keg, although not necessarily on a life cycle basis.

summary

In extreme areas, where temperatures, high loads or flammability are the focus, plastics are clearly superior. They are also well suited for applications with specific and complex requirements. Plastics are engineered to meet specific performance benchmarks, and a synthetic formula can (and likely has) been engineered for almost any combination of properties used in industry.

Relation

1. Dennis Lauer. “Selection of synthetic gear oils.” Machinery Lubrication magazine, May-June 2001.

Are you looking for different brands of gear oils on the market like Lucas Oil, Valvoline, Speedway Motors, CRC, Star Fire Premium Lubricants but don’t know where to start? We did a lot of research to find the 18 best gear oils available.

To compile our list of the best gear oils, we researched and ranked a number of the best selling gear oils on the market, ranging in price from $6.00 to $124.00. Based on our research, we think Lucas Oil gear oil is the best overall. Read on to see what other gear oils we highly recommend and check out our buying guide for all the information you need to know to make the best choice!

Description of the specification status

GL-1 Active The API GL-1 designation denotes lubricants intended for use in manual transmissions operating under conditions mild enough that virgin petroleum or refined petroleum can be used satisfactorily. Oxidation and rust inhibitors, defoamers and flow reducers can be added to improve the properties of these lubricants. Friction modifiers and extreme pressure additives must not be used.

GL-2 Inactive The API GL-2 designation does not identify lubricants intended for worm gear axles in motor vehicles that operate under load, temperature and sliding speed conditions such as lubricants satisfactory for API GL-1 service enough.

GL-3 Inactive The API GL-3 designation denotes lubricants intended for manual transmissions operating under moderate to severe conditions and spiral bevel axles operating under light to moderate speed and load conditions. These operating conditions require a lubricant with load capacities exceeding those that meet API GL-1 service but below the requirements of lubricants that meet API GL-4 service.

GL-4 Active The API GL-4 designation denotes lubricants intended for spiral bevel gear axles operating under moderate to severe speed and load conditions, or for hypoid gear axles (see note) operating under moderate speeds and loads will. These oils can be used in select manual transmission and transaxle applications where MT-1 lubricants are unsuitable. The manufacturer’s specific recommendations for lubricant quality should be followed.

GL-5 Active The API GL-5 designation denotes lubricants intended for gears, particularly hypoid gears (see note), in axles operating under various combinations of high speed/shock loading and low speed/high torque conditions.

GL-6 Inactive The designation API GL-6 designates lubricants which are intended for transmissions with very high pinion misalignment. Such designs typically require protection against gear scoring in excess of that provided by API GL-5 gear oils.

Information on the Ford 9-inch rear axle

The 9-inch Ford rear axle, so named because of a 9-inch sprocket diameter, is the choice of many circuit racers because of its strength, availability, and ease of maintenance. Manufactured by Ford Motor Company from 1957 to 1987, it was used in Ford, Mercury, and Lincoln full-size cars, ½-ton pickups and vans, and even some intermediates.

The Ford 9″ was produced with 28 and 31 spline axles, which even in their smallest form have a larger diameter than those of the 10-bolt Chevrolet rear axle. The gears and carrier have proven to be significantly stronger than the 10 and 12 hole Chevrolets, which use smaller 8-1/2″ and 8-7/8″ diameter cogs, respectively. The cases are also characterized by robustness with material thicknesses ranging from 0.150 inch to 0.250 inch thick.

The 9″ rear axle was manufactured in seven different shell widths, ranging from 57-1/4″ to 69-1/4″ wide, any of which may be ideal for a particular chassis. Determine the case width by measuring the distance between the axle flanges located at the outboard end of each axle tube. Some axes are more desirable than others.

Favorites among circuit racers include the rear axles of full-size ’66-’70 Fords and Mercurys, ’71-’72 Lincolns, and ’68-’72 F100 Ford trucks. This truck features 31 spline trucks, large ball bearings and is 61 inches wide. Many of these units also have larger 3-1/4 inch axle tubes. The only downside is that these axles have a 9-3/8″ diameter ring gear, but a traditional 9″ differential assembly can easily be swapped out.

Favorite leaf spring equipped Camaro or Nova race cars are the ’79-’81 Lincoln Versailles and ’77-’80 Ford Granada rear axles. These axles have extra heavy wall cases and come equipped with factory disc brakes, 28 spline axles, large ball axle bearings, leaf spring mounting pads and a 58-1/2 inch axle width.

All 9-inch rear axles share another benefit: a removable center section that allows the plate and pinion to be placed on a bench instead of in the housing. Gear ratios can be quickly changed by removing the axles and driveshaft, unbolting the center section, swapping out the ring and pinion, and reassembling. This feature allows racers to carry additional center sections fitted with different final drive ratios. The most desirable risers are made from strong ductile iron and are easily identified by a capital “N” cast on the outside of the casting. Heavy duty ductile iron and aluminum replacement parts are also readily available from Ford Racing and 9+.

The popularity of the 9″ Ford has resulted in the aftermarket producing a plethora of high performance parts designed primarily for racing applications. Complete cases, carriers, spools, mini-spools, axles, case ends, bearing and shim kits, sprocket retainers and yokes are all available from manufacturers such as Allstar Performance, Ford Racing, 9+, Ratech and Richmond. Spools and yokes are available in conventional steel, as well as lightweight aluminum and equally lightweight but expensive titanium versions for racers looking to speed up their lap times. Additionally, ring and sprocket manufacturers including Richmond and Motive Gear offer a wide range of gear ratios for racers looking for the perfect ratio.

All circuit racers should use a bobbin directly replacing the bearing carrier. A coil delivers equal power to both wheels, unlike positive traction units, which can be inconsistent. A spool is also lighter, simpler, and more durable because it eliminates breakable parts like the posi-traction unit, cross pin, spider, and axle gear.

Budget conscious circle track racers can use a mini spool, a special unit that inserts into the existing carrier to replace the spider and axle gears, effectively ‘locking’ the rear end like a traditional spool. A mini spool is also a much safer and more reliable way to “lock” the back end than the age old method of welding the spider gears. If a coil isn’t an option, another option is the “Detroit Locker,” a very heavy-duty limited-slip differential.

There are several helpful tips that will extend the life of the Ford 9″. Most replacement 9″ sprockets interfere with the area of ​​the housing where the sprocket guide bearing is located. Instead of machining the housing, the sprocket should be carefully chamfered with a small die grinder to ensure proper clearance. Rear wheels used in oval track applications should have either a special baffle or an internal case seal to prevent gear oil from collecting in the right axle tube.

If the rear axle being used has a stock Ford sprocket bracket, ensure it has the #HM89443 rear cone. A heavy-duty sprocket mount is highly recommended for any 9″ rear wheel. Heavy-duty “Daytona” style stays are available for standard 28 spline sprockets, use a larger bearing and are popular with oval track racers. Regardless of the application, all 9″ rears should come with a rear fill plug and cap for easy filling. Most experts agree that for best results and reliability, you should always use good quality racing gear oil.

Max Gear 85W-140 is recommended for use in truck and automobile marine engine front or rear differentials, manual transmissions and lower gear units that dictate the use of an API GL-5 or GL-4 fluid. It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.) and anti-sync. Max Gear is specifically formulated to extend gear and bearing life and offers superior corrosion protection over competing conventional and synthetic gear oils. We developed this ultra-hard, high-performance hypoid automotive gear oil to provide maximum protection for heavily loaded transmissions while maximizing performance throughout the drivetrain. Most importantly, Max Gear outperforms ordinary gear oils by combining the highest quality synthetic oils with Royal Purple’s proprietary Synerlec® additive technology. As a result, Max Gear keeps transmissions running smoother, quieter, cooler and longer without overhaul. A direct reduction in drag in the powertrain has a major benefit for trucks and other four-wheel drive vehicles, hence better fuel economy performance. Formulated with a Friction Modifier additive, therefore no additional additives are necessary. Max Gear is available in the following viscosities: 75W-90, 75W-140, 80W-90 and 85W-140

MAX GEAR 85W-140 HIGH PERFORMANCE GEAR OIL ADVANTAGES

Maximizes horsepower

Extends the life of gears and bearings

Reduces the operating temperature

Heavy service

Lower coefficient of friction

Excellent protection against corrosion

Separates quickly from water

Meets warranty requirements

Environmentally friendly

Formulated for use in limited slip differentials

Recommended use

Max-Gear is recommended for use in front or rear differentials, manual transmissions and lower gear units of marine truck, RV/RV and motor vehicle engines that dictate the use of an API GL-5 or GL-4 fluid. Formulated with hypoid friction modifiers required for use in clutch or cone differentials. Therefore, no additional additives are necessary with Max Gear 85W-140.

Changing the fluid in your Jeep JK’s front and rear differentials is an important part of routine maintenance. Fresh gear oil ensures your differentials are well lubricated and working properly. And unlike previous Jeep Wranglers, there’s no need to remove the differential cover. However, it is recommended that you do this from time to time (perhaps every other fluid change) as it gives you a chance to inspect your gears and identify any damage or unusual wear.

According to “Plan B” in the Jeep Owner’s Manual (heavy driving), you should change your differential fluids every 15,000 miles. However, it’s always a good idea to do this IF you have submerged your axes in deep water for any length of time. This post provides instructions on how to perform a Jeep JK differential fluid change applicable to either Dana 30 or Dana 44 axles.

The front Dana 44 differential uses 2.7 pints (1.35 quarts) and the rear uses 4.75 pints (2.375 quarts). If you have factory covers, all you have to do is fill your differentials until gear oil comes out of the fill hole. If you have an after-market differential cover that has a taller fill hole than the factory, DO NOT be tempted to add more gear oil than necessary. This results in an overfilled differential and gear oil being pumped out of the breather tube, creating a smelly mess. The transmission oil level only needs to reach the bottom of your axle tubes.

NOTE: Rear differentials with Trac-Lok (limited slip clutch differential, not used on Rubicon) require the limited slip additive for the clutch plates. You can also use synthetic gear oil as it contains friction modifiers.

Jeep JK Rubicon requires regular transmission oil. The Rubicon uses Tru-Lok, a mechanical lock, to lock the left and right axles together. Tru-Lok has no clutch plates, so no additive is required. On the Rubicon with Tru-Lok differentials, when the rear differential is unlocked, the vehicle uses the TCS (Traction Control System) to monitor the degree of wheel spin of each of the driven wheels. When wheel spin is detected, brake pressure is applied to the spinning wheel(s) to provide stability. This feature of the TCS system works similarly to a limited slip differential, controlling wheel spin over a driven axle. If one wheel on a driven axle spins faster than the other, the system applies the brake on the spinning wheel. This allows more engine torque to be applied to the wheel that is not spinning. This is how the Rubicon does without a locking differential at the rear.

As with any other fluid, refer to your Jeep’s owner’s manual for recommended transmission oil viscosity. I have a 2012 JK Rubicon with Dana 44 front and rear axles and the recommended gear oil is 80w-90.

Differential liquid capacity:

Jeep JK Rubicon Front Dana 44 2.70 pints (1.35 quarts)

Jeep JK Rubicon Rear Dana 44 4.75 pints (2.375 quarts)

Front differential without Rubicon 2.10 pints (1.05 quarts)

Non-Rubicon rear differential 3.80 pints (1.90 quarts)

Disclaimer: As I always mentioned, I’m not a professional mechanic, I’m just trying to get as much work done on my Jeep as possible. It helps me learn more about my vehicle and save some money that I can spend on parts and upgrades.

I take no responsibility for any injury or breakage that may occur if you choose to follow these steps. You must decide if you are happy with the work done on your jeep. If not, please have this project done by a professional.

As an Amazon Associate, I receive a commission from qualifying purchases. It allows me to offer content from this website for free to everyone.

Parts and tools needed:

1. 4 liters of 80W90 gear oil (use synthetic oil if you have a limited slip differential)

2. 3/8″ drive ratchet

3. 3″ ratchet extension

4. Oil pan

5. 3/8 hex bit (optional)

6. Brake Cleaner (Optional)

7. Funnel (optional)

8. Rubber gloves

9. Paper towels

Procedure:

Step 1:

Prepare your tools and get everything ready before you start the project. Park your jeep on a level surface, apply your emergency brake and put your transmission in park or put it in gear if you have a 6-speed manual transmission. Brake the wheels.

Step 2:

Make sure there is enough clearance and room to insert the new gear lube bottle into the filler hole and tilt it up. If necessary, you can jack up your Jeep’s frame and place it on jack stands to raise the tie rod and drag link higher above the differential.

Step 3:

Locate both the fill plug and the drain plug on your differential. Remove the filler plug BEFORE removing the drain plug. This way you can avoid draining all of the transmission fluid and then finding you have no way of filling the differential with fresh fluid.

Step 4:

Using the square head of a 3/8″ ratchet, remove the fill screw from your differential cover.

Some covers like Riddler use a filler screw that requires a 3/8 hex bit to remove.

Step 5:

With the filler plug removed, you can proceed to draining the old transmission fluid.

Step 6:

Place an oil pan under your differential. Then, using a 3/8″ ratchet with a 3″ extension attached, remove the drain plug from the base as shown.

Step 7:

Drain your differential oil completely before proceeding.

Step 8:

Your Jeep’s drain plug is magnetic and the inside end of it will most likely be fuzzy with fine iron filings. Use a paper towel and some brake cleaner to wipe the bolt clean. If you find any chunks of metal, consider removing the differential cover to inspect the gears (if you remove the cover you will need either RTV Silicone Gasket Maker or Lube Locker Differential Cover Gasket if you are reassembling).

Using a 3/8″ ratchet with a 3″ extension attached, reattach your drain plug to the base of your differential. Torque this bolt to 25 ft. lbs. of torque.

Step 9:

With the drain plug installed and tightened, proceed to topping up your differential with fresh gear oil. Fill in exactly the recommended amount of gear oil. If you still have a stock differential cover, you can stop as soon as fluid comes out of the filler hole.

Using the square head of a 3/8″ ratchet, reinstall the fill screw on the differential cover. Use a 3/8″ hex bit if needed. Torque the bolt to 25 ft. lbs. of torque.

Step 10:

Follow the same steps with the rear differential.

Make sure there is enough clearance and room to insert the new gear lube bottle into the filler hole and tilt it up. If necessary, you can jack up your Jeep’s frame and place it on jack stands to raise the tie rod higher over the differential.

Step 11:

Locate both the fill plug and the drain plug on your differential. Remove the filler plug BEFORE removing the drain plug. This way you can avoid draining all of the transmission fluid and then finding you have no way of filling the differential with fresh fluid.

Step 12:

Using the square head of a 3/8″ ratchet, remove the fill screw from your differential cover.

Some covers like Riddler use a filler screw that requires a 3/8 hex bit to remove.

Step 13:

Place an oil pan under your differential. Then, using a 3/8″ ratchet with a 3″ extension attached, remove the drain plug from the base of the differential. Drain the old liquid completely before proceeding.

Use a paper towel and some brake cleaner to wipe the drain plug clean. If you find chunks of metal, consider removing the differential cover to inspect the gears.

Using a 3/8″ ratchet with a 3″ extension attached, reattach your drain plug to the base of your differential. Torque this bolt to 25 ft. lbs. of torque.

Step 14:

With the drain plug installed and tightened, proceed to topping up your differential with fresh gear oil. Fill in exactly the recommended amount of gear oil. If you still have a stock differential cover, you can stop as soon as fluid comes out of the filler hole.

Using the square head of a 3/8″ ratchet, reinstall the fill screw on the differential cover. Use a 3/8″ hex bit if needed. Torque the bolt to 25 ft. lbs. of torque.

Step 15:

Pour the old gear oil into secure containers (use a funnel if necessary) and wipe away any debris. Take your Jeep for a test drive to a local auto parts store where you can dispose of used oil safely and free of charge.

If you have any questions or suggestions, you can leave a comment below.

Many people don’t know the differences between 75W-90 and 75W-140 oil. While it’s understandable to most car owners, it doesn’t mean that knowing these differences isn’t a good idea. The more knowledge you have, the better you can take care of your vehicle.

What is the difference between 75W-90 and 75W-140?

There is a lot of confusion about what these oils are and what they can do. Their names aren’t self-explanatory, but that doesn’t mean you can’t learn what they mean.

The two numbers in each name refer to the viscosity of the oil and the number of milliliters it takes to flow past an orifice. You should note that they are both great options in different situations.

What does 75W-90 mean?

75W-90 means that this gear oil has a viscosity grade of 75. This rating lets car owners know how thick or thin the oil is. The second number indicates that it takes one second for 90 milliliters to flow past an orifice.

What does 75W-140 mean?

Now that you know what the numbers in the first oil mean, you can probably guess what they mean for this lubricant. It has the same viscosity grade as the 75 listed. However, it is a thinner oil as 140 milliliters per second can flow past an orifice.

75W-90 and 75W-140 gear oil differences examined

To the uninitiated, the stats displayed by the name of each lubricant might not mean much. Therefore, knowing what these numbers mean will not get you any closer to deciding which option is better for you. Fortunately, there are many differences that we can explore. Here you can find out everything about the special features of these two types of gear oils.

Notable Properties of 75W-90 Gear Oil

Let’s take a look at some of the most salient features of 75W-90 gear oil. These features include:

overall performance

composition

oil pressure

viscosity

operating temperatur

mileage

price per quart

overall performance

75W-90 gear oil is commendably manufactured. It can be effective in most cars, but where it excels is in load-carrying vehicles. Even under heavy pressure, this gear oil withstands and ensures that you can do your job.

composition

Anyone who wants to know the exact composition of the mixture for this gear oil is out of luck. Unfortunately, most companies that make gear oil do not disclose information about their additive packages.

That being said, most gear oils consist of base oil (regardless of whether it is mineral, semi-synthetic or fully synthetic) and a combination of additives.

oil pressure

Oil pressure is an important characteristic to consider when considering transmission oil. Its density at 15 degrees Celsius is 0.86 g/cm3. Also, the 90 in its name indicates that it flows 90 milliliters per second.

viscosity

As mentioned above, the density of a given oil is indicated by the first number in its name. In this case, the gear oil under consideration has a viscosity class of 75. At 100 degrees Celsius, this lubricant has a kinematic viscosity of 15.7. However, when the temperature reaches 40 degrees Celsius, the kinematic viscosity is increased to 115.

operating temperatur

The improved thermal and oxidative stability of this oil allows it to work at temperatures between 149 and 177 degrees Celsius.

mileage

If you use this gear oil you should not notice a significant difference in your gas mileage. However, it should fare slightly better on the freeway than on city streets.

price per quart

The price of oil is constantly changing and as such there is no one price you can always rely on when buying oil. Different providers have different prices, so it’s a good idea to shop around. That being said, you should be able to get a liter of this oil for a little under $25 at most stores.

Notable Properties of 75W-140 Gear Oil

Now that you know more about 75W-90, let’s take a look at the properties of 75W-140 gear oil.

overall performance

You shouldn’t have any problems with this type of lubricant. It performs well in most conditions and works in most vehicles. Therefore, 75W-140 is a good option for car owners when thinking of changing from old gear oil.

composition

We discussed this when we were talking about 75W-90 gear oil, but manufacturers don’t usually release their additive packages. As a result, it is impossible to know exactly what is in each type of gear oil other than the base oil and a combination of additives.

oil pressure

This type of gear oil can operate under extreme pressure and is usually good for commercial use. Its density at 15 degrees Celsius is 0.89 g/cm3.

viscosity

The viscosity grade of this gear oil is 75, as indicated by the first number in its name. However, there are a few other key numbers to consider. Remarkably, the kinematic viscosity at 100 degrees Celsius is 26.1. However, when the temperature drops to 40 degrees Celsius, the kinematic viscosity increases to 177.7.

operating temperatur

75W-140 should work in most environments. This allows it to be operated in ambient temperatures from -25 degrees Celsius to 30 degrees Celsius.

mileage

Using this oil in your vehicle you should not see any significant changes in gas mileage compared to what you were previously given.

price per quart

The price of this type of oil is higher than the previous lubricant. A quart typically costs around $65, although this number can change significantly depending on where you buy it.

Pros and cons of 75W-90 and 75W-140 gear oil

Here you can see all the advantages and disadvantages of these two types of gear oil.

Pros Cons 75W-90 Gear Oil This type of oil offers better fuel economy than other options. It performs better than other options when temperatures are low. It is thicker at high temperatures, so it may struggle at higher temperatures compared to other options. You can expect this oil to lose its toughness quickly when subjected to heavier loads. 75W-140 Gear Oil It is thinner at high temperatures and therefore performs better in hot climates. Optimal for wear protection and durability. Fuel consumption is not as strong as other options. It does not work well at low temperatures.

You will find that the 75W-90 oil performs better at cooler temperatures while 75W-140 performs better at higher temperatures.

When should 75W-90 oil be used?

You can use this type of oil in most environments, although it starts to struggle in high ambient temperatures. Therefore, it is better to use this type of oil if you live in a temperate climate. You can use it in transmissions that limit the performance of API GL-5.

When to use 75W-140 oil?

This type of oil is fantastic in almost all situations. It works well in high resistance conditions, so it can be used in both light and heavy vehicles. It’s a solid option for road building, construction, and farming. However, you should note that this oil can start to struggle at low temperatures.

Which is better 75W-90 or 75W-140?

If you’re trying to figure out which of these gear oils is better, you can’t look for a black and white answer. Both types of gear oil have their strengths and weaknesses. Therefore, you must consider your current situation. If you live in a cold area you should consider using 75W-90, but if you live in a hot area you should use 75W-140.

The other thing to consider is whether you will be performing heavy tasks. In this case you should lean towards 75W-140.

Our recommended 75W-90 or 75W-140 gear oil brands

If you want to use 75W-90, these are some excellent gear oil brands:

valvolines

Mobile

Royal purple

Conversely, if you want to buy 75W-140 gear oil, you can look at these brands:

valvolines

Luke

Royal purple

frequently asked Questions

Here are some of the most frequently asked questions about these two types of gear oils.

Can you mix 75W-90 and 75W-140?

Sticking with the same transmission oil will make your vehicle more efficient. However, you shouldn’t have any major problems if you accidentally mix the two types of oil.

The likely result is that the two oils will combine in your vehicle. This means that together it has about the same effect as using 75W-115 gear oil. This is the number right in the middle.

You may run into problems when mixing oils with different viscosity ratings, but that shouldn’t be a problem as they have the same rating here.

Can I use 75W-140 instead of 75W-90?

Most people won’t notice much of a difference when switching between types of oil. This allows you to switch from 75W-90 to 75W-140. That being said, you need to be aware of the climate you live in.

In addition, switching to 75W-140 makes sense if you are going to be doing heavy duty work.

Is 75W-90 gear oil synthetic?

Yes, this type of gear oil is synthetic. It is formulated from a synthetic base oil and a combination of additives. However, the manufacturers have not published the exact ingredients.

Is 75W-140 gear oil synthetic?

Yes, it is a thermally stable gear oil specially formulated to exceed all performance requirements. Like 75W-90 gear oil, it uses a synthetic base oil and a combination of additives.

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Changing a car’s differential oil is one of the most overlooked maintenance tasks on light trucks, SUVs and non-front wheel drive passenger cars. Because the differential is in the back and under the car, it doesn’t get star treatment like the engine in the front.

But if the lubrication in the car differential fails, you won’t get very far. Luckily, you only need to change this oil every 30,000 to 50,000 miles.

⚠️As always, check your owner’s manual for how often to service your differential. Every car is different.

The differential is a component in all cars and is designed to compensate for the difference in the distance that the inside wheels and the outside wheels travel when the car is cornering. In a rear-wheel drive car, the differential has its own housing and lubrication, a thick, dark oil usually heavier than 80.

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Front drivers typically integrate the differential into the transmission case and share the same fluid. The differential oil lubricates the ring gears and pinions that transmit power from the drive shaft to the wheel axles. If your car is equipped with a limited slip differential, it also keeps all the moving parts in that assembly healthy.

A differential allows your car to take corners without drama. If both driving wheels turned together, they would jump because the outer tire goes farther than the inner one. There are many variations on the design, but they fall into three categories: open, limited slip, and torque vectoring.

Changing this oil is just as important as changing the engine oil, and for the same reason. Metal-to-metal contact wears surfaces and generates frictional heat, which inevitably weakens gears and leads to failure. Checking and changing the differential oil on a pickup truck is actually quite easy, but on a passenger car it’s a bit more difficult.

Either way, this little procedure can save you a big headache later.

Prepare the area

Loosen the screw at the very top of the cover, but leave the screw in place to prevent the cover from falling off completely and soaking the floor—and you—in differential oil. Nick Ferrari/Popular Mechanics

Depending on the design of your differential, this can be a very dirty job or a very clean job. Some differentials have a drain plug; others require you to remove the case cover. In both cases you need a wide drip tray; a plastic sheet underneath would be good insurance. Drive your vehicle for a few minutes to warm up the oil, then put on your dirty clothes – you’re likely to get dirty.

It’s just an oil change, right? Not that complicated, but get ready because old auto differential oil has the worst smell in the automotive world. At this warning, remove the filler hole plug at the top of the differential case, then unscrew the drain plug. If you don’t have a drain plug, unscrew the case screws and leave a few screws loose at the top to hold the cover in place.

Carefully pry the cover open with a regular screwdriver or the oil will spurt out and cover you in that unholy stench. Be careful not to damage the surface of the differential case. Drain the oil completely and then remove the cover.

Clean and seal everything

Nick Ferrari Nick Ferrari

Assume that all of the leftover oil in the axle is loaded with metal filings. If you’re an oil change scout, you don’t need to worry about this, but the rest of us should take the time to wipe the remaining oil from the case, gears, and the wet side of the home. Make sure you get everything as there might be some shavings hiding in the nooks and crannies.

💡A simple degreaser or just a set of shop towels is all you need to clean the case cover. Use gloves that you are happy to throw away. Once the cover is shiny, run a magnet around the inside to pick up any stray metal shavings.

Also clean the tip of the fill hole plug; Most are equipped with a magnet to grab fine metal particles. Don’t get mad about harsh cleaners – you don’t want the residue messing with your new oil. Take a razor scraper or light abrasive pad and scrape away the mating surface of the case and cover. Wipe both surfaces with a lint-free shop towel and brake cleaner.

Some cars have pre-made gaskets. If not, use a liquid gasket product rated for harsh conditions and oil exposure such as: B. Permatex Ultra Black. Place a single bead on the mating surface of the cover and draw a circle around each mounting hole, then screw the cover on using just enough clamping force to flatten the bead. Allow to cure according to directions, then use a torque wrench to tighten the bolts to your vehicle’s specifications.

Fill to the brim

Use a hose or pump to fill the differential with new oil if you cannot use the bottle alone. Nick Ferrari

Use the highest quality gear oil you can afford to fill the differential. The weight and capacity are listed in your owner’s manual; Your differential usually lasts up to 3 liters. However, be sure to read this manual as some limited slip differentials require a secondary friction modifying additive.

Fill the differential straight from the bottle if you have space, but if space is tight you can get a pump or extension hose to make the job easier. The bottom of the plug hole is the maximum fill line. So if oil drips out, you’re done.

Plug in, torque to spec, and you’re good for tens of thousands of miles.

Now look at this:

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Description of the specification status

GL-1 Active The API GL-1 designation denotes lubricants intended for use in manual transmissions operating under conditions mild enough that virgin petroleum or refined petroleum can be used satisfactorily. Oxidation and rust inhibitors, defoamers and flow reducers can be added to improve the properties of these lubricants. Friction modifiers and extreme pressure additives must not be used.

GL-2 Inactive The API GL-2 designation does not identify lubricants intended for worm gear axles in motor vehicles that operate under load, temperature and sliding speed conditions such as lubricants satisfactory for API GL-1 service enough.

GL-3 Inactive The API GL-3 designation denotes lubricants intended for manual transmissions operating under moderate to severe conditions and spiral bevel axles operating under light to moderate speed and load conditions. These operating conditions require a lubricant with load capacities exceeding those that meet API GL-1 service but below the requirements of lubricants that meet API GL-4 service.

GL-4 Active The API GL-4 designation denotes lubricants intended for spiral bevel gear axles operating under moderate to severe speed and load conditions, or for hypoid gear axles (see note) operating under moderate speeds and loads will. These oils can be used in select manual transmission and transaxle applications where MT-1 lubricants are unsuitable. The manufacturer’s specific recommendations for lubricant quality should be followed.

GL-5 Active The API GL-5 designation denotes lubricants intended for gears, particularly hypoid gears (see note), in axles operating under various combinations of high speed/shock loading and low speed/high torque conditions.

GL-6 Inactive The designation API GL-6 designates lubricants which are intended for transmissions with very high pinion misalignment. Such designs typically require protection against gear scoring in excess of that provided by API GL-5 gear oils.

1] The 9-inch Ford has no restrictions on the gear range of the differential case. A differential will accept any gear ratio from 2 to 6.

2] More gear ratios are available for the 9-inch Ford than any other rear wheel out there. Especially in the 3.0:1 to 5.0:1 range, there is usually a gear set for at least every tenth of a ratio change, making it easier to tune to a specific track. “You won’t find another rear triangle with more gearing options in both the street/strip and drag-race pro gear categories,” claims Quick Performance’s Brydon Papenberg.

3] A third drop-out item makes it easy to change gear ratios on the track as needed. You may already have additional centers set up and ready for installation (see photos A and B below).

4] A larger offset (hypoid distance) between the centerlines of the ring gear and pinion is the main reason the Ford is inherently stronger – but also why it is slightly less efficient.

5] A stout bolt-in pinion mount rigidly incorporates large tapered roller bearings to support the pinion (see photo C below).

6] A third “extra” pilot bearing supports the rear end of the pinion gear to limit gear deflection under high torque loads. Opinions differ as to whether it’s really a design improvement or a crutch (see Photo C below and “Rear Pinion Bearing: Strength Booster or Band-Aid?” section below).

7] The 9″ Ford Adjuster Nuts make adjusting the ring gear play easy: loosen one side and tighten the opposite side to move the gear back and forth. Most others use cumbersome, replaceable washers.

See all 34 photos See all 34 photos A] The Ford’s bolted third member (circle) holding the gears and differential, combined with bolted axles to allow for track changes in just 40 minutes. The axle tubes and center section are steel, making it easy to simply weld on various brackets to suit any rear suspension setup, as illustrated by one of Moser Engineering’s many ready-to-install 9-inch Ford assemblies.

See all 34 photos See all 34 photos B] As seen with Currie, you can pull out the axles and then slide the entire third element, including the differential case and pinion gear, right out of the case.

View all 34 photos View all 34 photos C] The bolted “capsule” pinion carrier contains two strong tapered bearings plus a small additional bearing (arrow) at the rear. Some claim this helps keep the drive pinion secure and supports it end-to-end for less deflection.

If you tell someone you have a 9-inch Ford, you’re automatically a badass.” — Tom, Tom’s Differentials

The Ford 9-inch rear was produced from 1957 to 1986. At one point it was installed in almost every Ford car and truck. In today’s racing and hot rodding, you’ll find these Hecks and their aftermarket descendants in just about everything – not just Fords.

But what makes the Ford “better”? Aside from an inherently large sprocket diameter (larger than all competing passenger rear suspensions, with the exception of the enormously heavy and relatively rare 9-inch Dana 60 rear suspension), the Ford’s greatest advantage over competing rear suspensions is its larger hypoid spacing. Hypoid clearance is the distance from the center of the ring gear to the center of the pinion. With approximately the same ring-pinion diameters, the inherent strength of the ring-pinion arrangement is higher, the greater this distance (or gear wheel offset). This is because staggering the gears at any point in time results in more surface contact between the gear and tooth. The benefit increases at lower (high numerical) final drive ratios because the low ratio gear sets have relatively fewer pinion teeth in contact compared to milder ratios – meaning fewer teeth to spread out and the load to take.

Ironically, what became one of Ford’s key strength advantages wasn’t due to the designers’ desire to increase rear strength. In 1957, Ford’s most powerful 312ci supercharged Thunderbird V8 produced 300 hp, with mainstream engines generally being in the 200 hp class at most. Instead, the large offset was a nod to placate stylists who wanted a lower floorpan with fewer “center humps” for the new Ford passenger car body.

As it turns out, in the performance world, the Ford’s “old-school” drop-out center section is another design advantage. “It’s one of the easier hecks to work with,” says Papenberg. “Not only does the drop-out design allow for easy swapping in and out of different gearing and carriers, but it also makes remodeling and maintenance easier because you can bench it right in front of you rather than working ‘within’ a complete one hecks.”

Overall, the Ford’s burly ring-and-pinion configuration, strong bearings, heavy-duty thru-axles, ease of setup, and future growth potential only contributed to the Ford’s increasing popularity in the hot-rod world. Today, aftermarket versions from Currie, Mark Williams, Moser, Hoosier Gear, Quick Performance, Strange, Tom’s Differentials and others have greatly improved the basic overall solidity of Ford’s original design, making it the go-to choice for racing and hot rodding alike. Summary of Papenberg: “New and improved parts are constantly being released for the 9-incher, which will further increase its popularity.”

See All 34 Photos See All 34 Photos This parts book style exploded view of a Ford 9″ third-party carrier shows all the major parts. Of particular interest – in view of the unique attributes of the design – are the extendable third element housing (3), the screwed-in pinion retainer (4) and the additional pinion shaft support bearing (11).

Hypoid distance: Advantage Ford

We know from years of experience that a full 9″ Ford is better and stronger than a Dana 60.” —Mark Williams, Mark Williams Enterprises.

With an offset of 2,250 inches, the 9-inch Ford’s hypoid spacing is greater than popular competitors, most of which are 1.5 inches or even less. “[Ford’s] hypoid angle gives it a huge advantage on the power side,” explains Quick Performance’s Brydon Papenberg. According to Hoosier Gear’s Bill Vandevord, the Ford can have a power advantage of up to 10 percent in certain cases, assuming co-sized gears. The strength benefit would be greatest as the gears get steeper (higher numeric) since the pinion gear generally has fewer teeth to take and distribute the torque loads. Ratios above 5:1 can only have five or six teeth. With a hypoid spacing of 1.5 inches, that equates to only 1.3 to 1.4 teeth in contact at any one time for a Chevy 12-Bolt, versus 1.7 to 1.8 for the Ford’s 2.250-inch offset.

But increased hypoid clearance is no picnic: In theory, it decreases efficiency because the pinion has to push harder against the ring gear at a lower contact point. And there is also more contact area, which creates higher surface friction. “More offset increases the contact ratio and creates a larger glide angle, which reduces efficiency,” says Vandevord. “A 9-inch Ford is only 93 to 94 percent efficient compared to a theoretical ‘on-center’ configuration.” Years ago, our sister publication Car Craft used a chassis dynamometer to conduct a real world evaluation and log the performance of the tires on a 12-bolt Chevy versus a 9-inch Ford. The Ford lost an average of about 2.6 percent versus a high-performance engine that peaked at 326 rwhp at 5,800 rpm.

Still, most racers are more than willing to trade such slight powertrain losses for real strength. “The ‘inefficient’ complaint with the 9-inch Ford rear really isn’t a big issue and probably wouldn’t be noticeable in 95 percent of the applications out there,” summarizes Quick’s Papenberg. “Newer, lighter and more efficient parts are becoming available, so any so-called gap is getting smaller. I would even say if you took the same car with the exact same setup and put them side by side using the same driver in multiple circumstances then that driver would not be able to tell which rear end is in the vehicle.

See all 34 photos See all 34 photos With its huge 9″ cog, a beefy Dana 60 should be stronger than a 9″ Ford. But as these photos from Hoosier Gear show, the Dana 60 (left) only has a 1,062-inch hypoid offset compared to the Ford’s larger 2,250-inch (right). Less gear offset means the Dana has less power-enhancing tooth contact compared to the Ford, but slightly higher theoretical efficiency.

See all 34 photos See all 34 photos When a 9 inch cog diameter is not enough, there are 9.5 and even 10 inch cog sets. The 10″ cogs usually require a special aftermarket third part, but Hoosier Gear offers 10″ cogs that fit “regular” 9″ cases (release may be required). Compare a “standard” 9310 alloy 4.57:1 Hoosier gear set (left) to the 10″ version (right).

See all 34 photos See all 34 photos When a rear end becomes really popular – like the 9-inch Ford – it spurs the development of even better parts that will feed themselves and create even more popularity. Available from Quick Performance, this serrated pinion gear is over four kilograms lighter (depending on gear ratio) than a standard weight gear. The heat-treated alloy steel 8620 gears are said to be suitable for street, drag racing, circuit track and off-road use.

Rear sprocket bearing: booster or patch?

Ford 9″ rears have a third “extra” pinion support bearing located at the rear of the drive pinion. Other rear triangles only have the usual two support bearings in the middle. The traditional view of the Ford’s extra bearing is that it is a brilliant design improvement that puts the pinion in double shear to prevent pinion deflection. However, some consider it an extra patch solution: to allow for all the internal guts to be pulled from the front, the two large main bearings up front are closer together than they ideally should be, to support the beefy drive pinion and a teetering wobble. Already in production, Ford realized that the rear bearing was really too small, and increased it slightly on the third element of nodular iron “Daytona”. The size of the warehouse has gotten even bigger with custom aftermarket racing third parties.

See all 34 photos See all 34 photos The 9-inch engine’s controversial rear pinion support bearing (arrow) is said to increase strength, but it could really be a patch as the traditional two front bearings are too close together.

See all 34 photos See all 34 photos As performance increased, Ford found that even the ‘third’ pinion shaft support bearing was inadequate. In the early 1960s it introduced the “Daytona” pinion bearing retainer, which accepted a slightly larger bearing. It is still available from Ford Performance under PN M-4614-B. Even larger bearings and 35 tooth sprockets are available through aftermarket sources.

shades of grey

The 9-inch Ford is a great heck – when built properly with modern aftermarket parts. Unfortunately, very few factory 9-inch Ford installations had all the good stuff, making it highly unlikely to achieve a bulletproof version at the junkyard. For example, most versions have a cast iron third link, not the desirable ductile iron body. “They’re only good up to a maximum of 400 hp,” says Tom of Tom’s Differentials. “Anything beyond that should use today’s improved, redesigned aftermarket ductile iron cases. They are good to 800hp if built right. The next step up would be the completely redesigned Mark Williams top-of-the-line billet aluminum case.

“The same goes for standard production 28-spline axles. I never use them when building from scratch. You need at least 31 spline axles for any decent road car, but today I go straight to 35 spline axles on scratch builds.” And yes, there are up to 40 spline axles available. Then there’s ring and trunnion larger diameter 9310 high alloy steel; depending on specific design they may or may not require a redesigned and aftermarket approved third element.

See all 34 photos See all 34 photos The overall design of the 9-inch Ford lends itself to easy adaptation to all types of non-stock applications. Aftermarket tail specialists like Currie have hundreds of cases on standby just waiting to find a home on your hot rod or race car.

See all 34 photos See all 34 photos Many high-end racers and professional rear wheel builders prefer Mark Williams’ completely redesigned, rugged cast aluminum third case (shown). Says an authority, “I’ve never broken a Williams case in 15 years. They typically last 100 rides in a Pro Mod car.” Strange also offers a high quality billet aluminum body.

See all 34 photos See all 34 photos We’re running low on junkyard 9″ rears. Today, most high-performance 9-inch Fords are built from entirely new parts – even the pipes and banjo are made from the ground up, like this high-end assembly from Currie Enterprises.

No other Heck has the same aftermarket fan base as the 9-inch Ford. The strength-to-weight ratio of the 9-inch Ford rear is hard to beat.” —Brydon Papenberg, Quick Performance

See all 34 photos See all 34 photos A variety of limited slip differentials were offered for the 9-inch. This is a typical parts view of a Traction-Lok ​​differential. This fully field-convertible, limited-slip design uses clutches similar to a Chevrolet Eaton-style positraction setup.

See all 34 photos See all 34 photos Trac-Lok convertible limited-slip differentials are still available directly from Ford Performance Parts (28-spline, PN M-4204-F28A; 31-spline, PN M-4204-F31A, shown).

See all 34 photos See all 34 photos Strange was Ford’s OE supplier for the 9″ tails used in the 2010 factory Cobra Jet Mustangs. The same base assembly bolts into 2005-2014 Mustangs. Strange offers an endless variety of options.

See All 34 Photos See All 34 Photos The cover may fool you, but this is a bolt-on Currie 9-inch Ford Crate rear in an early Chevelle. The optional inspection cover makes the beefy 9-inch Ford look almost like a stock installation.

contacts

Currie Enterprises Inc.; Corona, CA; 714.528.6957; CurrieEnterprises.com

Ford Performance Parts (FPP); Dearborn, MI; Tech: 800.367.3788 or 313.621.0771; PerformanceParts.Ford.com

Hoosier gear; Centerville, IN

Kentucky differential; Louisville, Kentucky

Mark Williams Company; Louisville, CO; 866.508.6394 or 303.665.6901; MarkWilliams.com

Moser Engineering; Portland, IN; 260.726.6689; MoserEngineering.com

Fast performance; Ames, IA; 515.232.0126 or 515.291.1968; QuickPerformance.com

Strange Technique; Morton Grove, Illinois; 847.663.1701; StrangeEngineering.net