Stop Differential Failure

Avoid Differential Failures – simple secrets to enable your OEM Differential to last a million miles (really)

A former OEM headquarters senior engineer explains:

  • Summary of your differential’s basic maintenance needs, so it can last 500,000 miles or more (without repair).
  • Overview of the real issues and problem sources that cause differential failures.
  • How to make your differential “bullet-proof” in tough commercial use and heavy towing: never lose another rear-end!
  • The surprising #1 reason why differentials fail in cars, 3/4 and 1-ton pickups, as well as larger GVWR fleet trucks.
  • The secret #1 thing to do ONE TIME to maximize your new vehicle differential’s lifespan… is EASY! (It’s #2 below.)
  • Why your choice of differential gear lube makes so much difference, and why a good synthetic is essential.
  • Fourteen revealing ASTM tests for differential gear lubes that no one tells you about, and the results of those tests on 14 different gear oils.
  • How you can apply the same secrets to prevent your transmission from failing.

A Summary of Basic Differential Needs for Long Life

(How to Stop/Prevent Differential Failures):

(Each of these has detailed sections, further below)AMSOIL is devoted to protection

  1. Observe the break-in period carefully: speeds under 50 mph, only short trips, keep the pedal below half-throttle, and NO TOWING OR HAULING for the first 3,000 miles. This is essential to prevent the differential from reaching higher temperatures that cause rapid lubrication break-down.  If this is not possible in a commercial application, well-planned preparation upgrades are essential to avoid early differential failure.
  2. Perform the first gear lube change at 3,000 to 5,000 miles, using a high-performance synthetic gear oil which you selected from ASTM test performance data – not marketing.  3,000 – 5,000 miles is considered by most axle manufacturers as the end of the break-in period.  When changing the gear oil, be sure to find and clean the differential magnet carefully, to make sure that it can continue to capture and hold hard iron particles.
  3. Do not allow wheel spin, especially with intermittent good-to-poor traction (such as snow/ice/sand patches on dry pavement): it produces excessive wheel speed, which combines with sudden tire traction to create a high-energy shock-load.  The peak power of the shock spike will cause damage, and can even fracture internal differential parts or other drivetrain components such as universal joints.
  4. Periodically inspect the breather fitting and breather tube for cracks, splits or leaks: these conditions can allow both gradual water intrusion from weather, and sudden catastrophic water intrusion from flooded roadways or backing down a boat ramp. Sudden water-cooling of the hot differential creates a vacuum that rapidly sucks air (good) or water (bad) inside, like drinking from a straw. Very few gear oils are designed to provide adequate lubrication when water contamination is present: essentially, in a chemical and functional sense, most gear oils “fall apart” when you add water.  (Boaters beware!)
  5. Upgrade the differential cover when engine torque/horsepower upgrades are made, or if you will be towing a heavy trailer: most aftermarket differential covers not only add cooling, but also add rigidity that reduces differential flexing under higher torque loads. If you are going to tow heavy loads, or tow regularly, or tow in the hills or mountains, you should select a new differential cover that not only increases cooling but allows you to put a sensor in the differential and add a differential temperature gauge to your dashboard instruments.

Tip:  If your differential starts making a whining or growling sound, that typically means your lubricant level is low and your lubricant is completely shot.  Immediate therapy is required to minimize the damage to your differential and extend its’ life.  At minimum, our best recommendation is to stop driving the vehicle until you can clean out the differential and fill it up with AMSOIL Severe Gear Synthetic lube oil.  If you must drive it temporarily, add a fully synthetic gear oil to the full point: if this eliminates the noise, then a second step of cleaning and refilling with AMSOIL may save the differential.

If you find any metal chunks or pieces in the bottom of the differential, it is essential to have a qualified differential mechanic inspect and repair the differential – not just a general mechanic. If it is making a thunk/clunk sound every two feet to 10 feet, you have gear tooth damage.  Driving under any of these conditions can rapidly worsen the damage and create more expense. If you must drive it to the shop rather than tow it, pretend you are an 80-year old woman driving with a grand-baby laying on the seat beside you (not in a car-seat).

Differential Ring gear and Pinion gear meshing is loading only two teeth

Overview of Differential Issues and Problem Sources

The requirements for automotive gear lubrication have changed over the years, yet vehicle owner awareness has not. Gear lubrication has been commonly considered elementary, but in reality gear lubrication is a dynamic process that requires advanced technology. The differentials that house the gears are out of sight, out of mind, and neglected. But differentials are just as important to the vehicle as the engine: an engine without a functioning differential will not move the vehicle.

While engine break-in has become less important than in the past, due to materials engineering and design advancements, this is not true of transmissions and differentials. The differential, in particular, is as sensitive or more sensitive to the break-in period than ever.  This is largely due to the differential’s nature as a brute-force mechanical gear assembly which generates significant heat and wear particles during break-in, yet it has no cooling system to reduce peak temperatures, and no filter to remove wear particles.

The differential’s break-in period is the time where the rubbing metal surfaces are being polished to fully match each other.  This is especially important and applicable to the ring gear and pinion gear.  This break-in polishing process generates a lot of wear particles and a lot of heat, and the heat is both degrading the oil and increasing the amount of frictional heat that is being created.

NEVER tow ANYTHING during the break-in period. (If you have no choice, see below for how to protect your differential.)  Heat buildup is why towing/hauling during this break-in time can actually create rapid failure of the lubricant and the differential. In a death-spiral known as “thermal runaway”, the differential gets hotter and hotter until it completely fails. Lesser heat for shorter periods is also damaging, but the shortened life of the differential may not produce symptoms or failure for thousands, or tens of thousands of miles.

Many people think that it is common or expected for differentials to fail after 60,000 to 150,000 miles.  Or they believe that OEM designs or defects are at fault.  A common perspective of many owners of small fleets was expressed by one who said “not one OEM makes a truck with a decent differential – they never last”.  It’s not true.

The sobering truth that OEM’s don’t talk about?  Most differentials fail because their gear oil failed a long, long time ago.  In reality, most differential failures are Tranny Fluid Life Chart of Miles vs Temperature (F)completely unnecessary… and fully preventable.

Refer to the chart at the right which shows transmission fluid life compared to fluid temperature.  This situation is very similar with differentials, because the real issue with both transmission and differential life is the life of the lubricating fluid. Heat rapidly degrades lubricant life. 

The stress of increased temperatures during the differential’s break-in period was documented in 2005 in an SAE paper titled “The Effect of Heavy Loads on Light Duty Vehicle Axle Operating Temperature”. A light duty GM truck towing 14,000 pounds was driven from Orange County, California to the Nevada state line in the test, and the trip was performed with both a new axle and a broken-in axle.
During level ground towing, oil temperature measured 230 degrees F in the new axle, but 203 degrees F in the broken-in axle. Oil temperature over the most grueling part of the trip, which included a maximum 6% grade, recorded that the new axle was operating at 350 degrees F and the broken-in axle was operating at 300 degrees F.  Similar results showed up in laboratory dynamometer test results simulating a truck hauling a trailer, with the equivalent of level ground towing temperatures recorded at 266 degrees F with the new axle and 194 degrees F with the broken-in axle, while a 3.5% grade produced differential towing temperatures of 370 degrees F with the new axle, and 295 degrees F with the broken-in axle.

Unfortunately, the temperature situation has gotten even worse with newer vehicles.

For long differential life, gear lubrication needs to be taken more seriously than ever before. There are several forces driving the need for better gear lubrication:

  • First, is improved fuel economy. Modern vehicle aerodynamics use lower elevations of the front air dam , which decreases the air flow over differentials. Fuel economy is improved, but reduced air flow increases differential operating temperatures. Also, lubricant fill volumes in differentials have been reduced to lower fluid drag on the gears and bearings, and to lower differential weight, for further improvements in fuel economy. However, lubricants cool components: with less fluid in the sump, the operating temperatures rise.
  • Improvements in vehicle performance have created additional need for more sophisticated gear lubrication. Each model-year of turbo diesel pickup trucks, V-10 gasoline pickups and sport utility vehicles (SUVs), and high-horsepower V-8 trucks introduces more towing and payload capacities than in previous years, yet their differentials have not changed.
    There was a 34% increase in engine horsepower over the 1997-2007 decade, while axle gear sizes have remained constant, sump capacities were lowered and drain intervals extended. In the light truck segment there was a 93% horsepower increase from 1981 – 2007.(1)  In vehicles such as a fifth-wheel equipped Ford F-350 Super Duty, towing capacities reached a high of 19,200 lbs(2), and continue to climb.  Meanwhile, testing shows that in new axle applications simulating trailer towing at 88 km/h (55 mph) at a 3.5% grade temperatures can reach as high as 188°C (370°F).(3)  At such temperatures, the life of petroleum gear oils is best measured in minutes.
    Stress on differentials has also increased in limousines, conversion vans, and trucks and cars with modified, high-performance engines. More power, more towing capacity and higher hauling limits greatly increase the stress that causes heat and wear.
  • Even improvements in vehicle comfort have driven the need for better gear lubrication.  The demands for greater interior space have forced vehicle manufacturers to lower floor boards, which restricts air flow to the differential. Hot exhaust systems are forced closer to the axle housing, and differential operating temperatures climb even higher.
  • Most vehicles operate under severe service as defined by vehicle manufacturers, but most vehicle owners are unaware of this.  Severe service applications include towing, hauling, plowing, off-road use, frequent stop-and-go driving, steep-hill driving and temperature extremes. Severe service applications are on the rise. For example, more than 90 percent of Ford Super Duty pickups are used for towing.(4)  Severe service increases the need for better gear lubrication.

Synthetic gear lubes are recognized as superior to petroleum-based gear lubes by vehicle manufacturers, gear manufacturers and most high-performance automotive experts.  Synthetic gear lubes exhibit all-around better performance, and have been in most tractor-trailer differentials for over a decade.  There are many synthetic gear lubricants available to consumers, including those marketed by vehicle manufacturers.  But because all lubricants position themselves as superior to the rest, it is difficult for consumers to make informed choices. (Fortunately, UltimateSyntheticOil provides real data – see below.)

Operating Conditions and Lubrication RequirementsCloseup of Differential Ring Gear and Pinion Gear meshing together

Differentials contain many different component types, each having its own requirements for lubrication. The ring and pinion gears operate under extreme pressure and sliding contact that require extreme-pressure additives for protection. The bearings operate under rolling motion where lubricant film strength is particularly important, and limited-slip clutches require special friction additives for proper operation. So it is essential that gear lube formulations be carefully balanced to protect all components. Too much emphasis on the needs of one component usually neglects the needs of another component.

In addition, the fact that differentials are loaded more heavily than ever while having less cooling than ever, means they run hotter.  Differentials experience higher average temperatures and higher peak temperatures, especially when towing in hills and mountains.  Under these higher heat loads, high-performance synthetics have become essential to long differential life.

On the other extreme, very cold temperatures can also be detrimental to differentials.  Petroleum gear oils perform poorly both at high operating temperatures and at low operating temperatures.  And an oil whose performance has been damaged by high temperatures will also perform worse at cold temperatures.

When you consider all of the demands placed on differentials, it is easier to understand how a mediocre gear lube and inadequate fluid changes will deliver short differential life.  Likewise, a top-performing gear lube has potential to dramatically extend differential life.

Owners – Managers: Click Here to APPLY FOR AN AMSOIL COMMERCIAL ACCOUNT. Fleet – Facility – Equipment. Get the Best Pricing PLUS Expert Engineering AdviceAs we detail in the seven lessons of the Million Mile Van, a top quality synthetic gear oil can enable a 700,000 mile differential life – or longer.  The van’s differential lasted 400,000 miles after its’ FIRST AMSOIL Severe Gear synthetic oil change.  Unfortunately, the owner forgot to put the differential on his maintenance schedule, which wore out the bearings 400,000 miles after AMSOIL Severe Gear was installed.  After replacing the “needle bearings”, the last we knew, it had traveled another 700,000 miles without problems by doing 150,000 mile AMSOIL gear oil changes.

For vehicle owners, clearly one of the most important questions is this:  how can I pick a gear oil that really IS high performance?

The answer: base your choice on ASTM testing data.  The lubrication industry has a “don’t ask, don’t tell” approach with consumers: they know that consumers don’t ask for the results of the ASTM testing that the entire lubrication industry relies on, and they don’t tell consumers that these ASTM bench tests exist which they perform all the time. Nor do they share their ASTM test performance data with the public.

Fortunately, AMSOIL is the king of published test data.  They publish ASTM test data conducted by independent certified laboratories, and the ASTM results are so reliable and accurate that not one of the many oil companies has dared to complain or filed a lawsuit for inaccurate test data.

So that you can understand this situation more clearly, review the comparative ASTM test data on gear lube performance below. This landmark study combined the common lubrication industry tests with some severe-service standards (such as federal Military test standards), to fully measure the engineered performance of these gear oils.  This study has been retired (“archived”) by AMSOIL, since not all of the lubricant formulations are current products.  But as the first of its’ kind, it is an amazing eye-opening perspective for people who have never seen “behind the curtain” of the lubrication-industry to realize that lubrication performance is not based on wizardry, but on engineered formula development using the well-known, published, standardized ASTM performance testing.

Superior technology is never produced by marketing slogans, and it’s not accidental – it’s carefully engineered.

Any marketer can make opinion statements, emotional appeals, and unsupported claims. But DATA is where engineering battles marketing to WIN on the field of reality!

The Gear Lube Research White Paper of Comparative Testing on 14 Gear Oils

Here is a quick overview of the charted results of 14 API ASTM tests from the legendary Gear Lube Research White Paper, which was published by AMSOIL in 2007.  These long-established standardized engineering tests are used by the API and SAE, as well as European and Japanese car manufacturers and the US military, to reliably measure the important performance characteristics of gear lubricants.  The 14 tested gear oils included Mobil 1, GM, Mopar, Lucas, AMSOIL, Pennzoil, Redline, Royal Purple, Castrol, Valvoline, and Torco.

{Spoiler Alert:  these tests reveal the carefully engineered overall excellence of AMSOIL’s Severe Gear 75W-90, with all tests performed by a certified independent lubrication test lab.  After several years the research paper was archived by AMSOIL, since multiple formulations had been changed.  However, as of 2016, not one company has challenged the validity of these publicly distributed test results.  The two un-changing realities are that most oils are formulated for profitability rather than performance, and that AMSOIL is legendary for their passionate pursuit of the best performance that new technologies and methods can enable.}

Chart of tested differential gear lubricants includes AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Viscosity Index ASTM D-2270 test results for 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Viscosity before and after KRL 20-hr Shear Stability Test for 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Percent viscosity change from shear test for 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Cold temperature Brookfield viscosity chart showing all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of Cold Pour Point ASTM D-97 test results for 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of MIL-PRF-2105E FTMS 791C Cold Channel Point Test results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of ASTM D-2893 Oxidation Test results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Carefully note the following four Extreme Pressure and Wear tests.  In three of these four critical performance tests, you can see that all three petroleum oils are among the worst 5 performers. The key reason for this is that synthetic base-stocks have 7 to ten times the film strength of petroleum oils, before including any additives.  So these tests highlight one of the worst mistakes you can make, which will absolutely shorten your differential’s life: using a petroleum gear oil.

Chart of 4-Ball EP Weld Point ASTM D-2783 Test results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of 4-Ball EP Load-Wear Index ASTM D-2783 test results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of Falex Extreme Pressure Test ASTM D-3233 results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of 4-Ball Wear Test ASTM D-4712 results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of Foaming Tendency ASTM D-892 test results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Chart of ASTM D-130 Copper Corrosion Classifications, Limits and Test Results for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

Two Major Points to notice in the testing:

  • First, of the 14 gear oils tested, only two passed all the minimum test requirements.
  • Second, in several important tests, the three petroleum oils were ALL among the five worst performers.

To summarize the results of all the tests into a sense of overall comparative performance, AMSOIL assembled this simple summary scoring chart. It is not weighted for importance of the tests.  Red numbers indicate test failures, and lower scores are best.  (See the report for explanation of the scoring details.)

Gear Oil Testing Summary Score Chart

Summary Chart of all Test Scoring for all 14 differential gear lube oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

We encourage you to read the full archived report paper, which can be reviewed here.

Appendix 3 details the performance of the AMSOIL Severe Gear when subjected to the grueling ASTM D-6121-06 “L-37 Axle Rig Test” which was modified with a 20% increase in loading, to provide even greater test severity.  This was equivalent to a Duramax 6.6 liter engine connected to an Allison transmission in second gear (1.81 to 1) with a differential gear ratio of 3.55 to 1, going up-hill, pulling a loaded trailer heavy enough for the engine to develop and maintain 650 ft-lb of torque under full-throttle operation for 24 straight hours.Save up to 25 percent and get exclusive offers as an AMSOIL Preferred Customer PLUS exclusive help from a former OEM headquarters senior engineer

The expensive L-37 Axle Rig Test was designed to simulate a grueling real-world environment, and the results confirm that the 14 ASTM “bench tests” of the oil properties do correlate to actual performance in a vehicle differential. The teardown gear inspection revealed that AMSOIL passed the test with flying colors: very little gear wear occurred, and roller bearing condition was “like new”.  The 15 ASTM tests together confirm, for example, that AMSOIL Severe Gear would provide excellent differential protection for Ford PowerStroke, Ram Cummins, and GM Duramax turbo-diesel pickups which are towing heavy trailers cross-country through hills and mountains.

AMSOIL outperforms other gear oils in many respects, but the central core is that they enable the differentials to run at much cooler temperatures while also being more resistant to break-down of the lubricant and additives at higher temperatures.  This enables them to provide superior protection, and to provide it for far longer than other gear oils.  In fact, AMSOIL’s differential gear-oil performance has a long and formidable history of excellence and superiority.

Bobby Unser:  (3-time Indy 500 Winner, 35 overall Indy Car wins, & 13-time Pikes Peak Hill Climb Winner.)

During AMSOIL’s 30th anniversary convention in the summer of 2003, Bobby Unser got up on stage and told about how his race car differentials could not survive more than one race up Pikes Peak without needing to be rebuilt… until he started using AMSOIL. Then his differentials went all race season without needing to be rebuilt. This experience in Bobby’s early years of racing began his long relationship with AMSOIL in all his race cars.

Bobby went on to say that:

“AMSOIL is the Best Lubricant made, the Standard to which all others are judged.”   – Bobby Unser

Gear Lube Cost vs Pricing

A gear lube’s price is often a key consumer consideration when selecting a gear lube. Price, however, does not reflect the actual cost of a product. Less expensive oils may save money initially, yet cost more in the end if the products compromise performance or require more frequent oil changes. Ford, for example, requires petroleum gear lubes to be changed every 3,000 miles under severe service but waives that requirement for synthetic gear lubes, extending the service life.(6)  In AMSOIL’s 2007 study, the three lower-priced petroleum SAE 80W-90 gear lubes had consistently lower test scores in the 4-Ball EP and Falex Tests.

Generally, lower performance comes with lower price and higher prices typically provide higher performance. But there are exceptions. Lucas 75/90 Synthetic and Royal Purple Max-Gear Synthetic 75W-90 demonstrated that higher price doesn’t always provide higher performance.  The benefits from a well-engineered, although higher-priced gear lube, can easily offset the higher per-quart price. Paying a little more for a quality lube that delivers the right performance is a low-cost investment to protect high-priced equipment.

Among all 14 gear oils, only two passed ALL the minimum requirements of the tests.  One of those two, AMSOIL’s Severe Gear 75W-90, illustrates a superior-performance low-cost choice, because it is rated for 100,000 mile fluid changes in normal service, or 50,000 miles in severe service.  (The Million Mile Van successfully used 150,000 mile fluid change intervals for both the transmission and differential, but this extended fluid-change interval was possible because the van was only hauling internal cargo loads in cross-country delivery transit: not towing a heavy trailer.)

The pricing chart (below) was obtained in 2007 by purchasing a 12-quart case of each product from the manufacturers or distributors and calculating the cost per quart.

Gear Lube Price Comparison Chart for all 14 differential gear oils from AMSOIL, Castrol, GM, Lucas, Mobil 1, Mopar, Pennzoil, Red Line, Royal Purple, Torco and Valvoline.

AMSOIL’s Severe Gear was clearly the best overall performer, and is reasonably priced. But naturally, all of the oil costs have increased since 2007.  SaveUpTo25Percent

How can you get the best pricing on AMSOIL products including synthetic gear oils and other synthetic oils and filters?

Easy.  We recommend that you become a Preferred Customer through – this not only gives you wholesale dealer pricing, with products arriving typically in 3 days to your doorstep, but also gives you the rare benefit of our expertise and recommendations, for free.  Only a few AMSOIL dealers can offer you the expertise of a mechanical engineer and lubrication specialist who spent over 15 years in automotive, was a senior OEM engineer, and is an AMSOIL University graduate.  It is our expertise, in recommendations and explanations for your application, which is invaluable to maximizing your vehicle life and enabling the lowest maintenance costs. (More about us.)

Differential Covers:

DiffCoverIf you are towing, or hauling, or plowing snow for a living, or if you occasionally tow a vacation trailer, or if you have an RV motorhome, you should never use anything but AMSOIL Severe Gear Synthetic oil in your differential.  (That’s an engineering opinion, not a marketing ploy: deviate at the peril of your own pocketbook and stranded vehicle.)  For these applications you should use only AMSOIL Severe Gear 75W-140 or 75W-110, not 75W-90.  The AMSOIL Severe Gear 75W-110 is a great overall choice that will give you ~80% of the fuel economy benefit of a 75W-90 (vs 75W-140), with ~80% of the wear protection benefit of a 75W-140 (vs 75W-90).  These AMSOIL gear lubricants provide maximum protection with the best available technologies on the globe, and they run cooler and minimize wear, while providing extended drain-interval life.

Tip: If you buy a used vehicle, assume that the differential gear oil has NEVER been changed, because the odds are over 90% that it hasn’t: make it a priority, buy your own gear oil and either change it yourself or take it to a trusted mechanic. (One national quick-lube chain estimates that only 1-2% of their customers will ever buy a differential fluid change. Investigative reporting suggests that in some chains, nearly half of the paid differential fluid changes will be “ghosted” services: never actually performed. Such fraud is far too common.)

If you are buying a new vehicle for commercial application, and cannot ensure that it is babied for the first 500 miles and preferably 3,000 to 5,000 miles (in cases such as an uplifted and tool-ATS Differential Cover for increased cooling and oil capacityloaded service truck), then your differential failure will occur too early and will not be covered under warranty. To preserve the differential and maximize its’ life on a brand-new commercial vehicle, we recommend these immediate steps:

  1. Upgrade the differential cover to obtain more cooling and more fluid capacity, and to install a differential temperature gauge on the dash.
  2. Fill the differential with AMSOIL Severe Gear lubricant.
  3. Instruct the driver to pay close attention to the differential temperature for the first 5,000 miles, especially when climbing grades, and to keep it below 250°F. (This gives some headroom if they don’t notice a rapid temperature climb.)
  4. At 10,000 – 15,000 miles, change the AMSOIL Severe Gear fluid.  (Use of AMSOIL extends the break-in period.)
  5. Put the differential on a 50,000 mile fluid change interval for the AMSOIL Severe Gear fluid – or up to 150,000 miles as indicated by oil analysis sampling.

In any case, ALWAYS make your change to AMSOIL Severe Gear before you tow ANY trailer.

For all tow/haul applications we recommend that you replace your differential cover with one of the top-quality aftermarket differential covers, and that you install a temperature sensor in the cover with a gauge on your dashboard.

Superior differential covers are available from quality designers and manufacturers such as PML, or Mag-Hytec.

An Aluminum differential cover provides several valuable advantages:

  • Increases mechanical rigidity of the differential assembly, which reduces wear rates and damage during severe loading conditions.
  • Adds additional lubricant capacity, which absorbs more heat and therefore reduces peak temperatures when climbing long grades.DiffCover-aFe
  • Adds additional cooling capacity because of the larger cover size, aluminum material, and cooling fins.  (Remember, operating temperature is the key factor in lubricant properties and life.)
  • Enables adding a temperature gauge to your dash, which allows you to judge your towing conditions and gear-oil life based on the temperature.
  • Makes it easy to check gear-oil level and condition.
  • Enables you to pull an oil sample for lab analysis (optional, an analysis tells you when you need to change your oil, and how healthy your differential is)
  • Makes it easier to change gear-oil.
  • This visible upgrade looks great, and marks you as a wise, informed vehicle owner.

Fleet Owners – Safely Extend Oil Drain Intervals:
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1. Richardson, Robert; Marsic, Vera; Tarrant, Simon:
“Driveline Fluids – Thermal Management Challenges and
Impacts on Base Oil and Additive Technologies,” National
Petrochemical & Refiners Association Annual Meeting,
Paper AM-05-32, March, 2005.

2. 2007 Trailer Life Towing Guide.

3. O’Conner, B.M.; Schenkenberger, C.: “The Effect of Heavy
Loads on Light Duty Vehicle Axle Operating Temperature,”
Powertrain & Fluid Systems Conference and Exhibition,
SAE Paper #2005-01-3893, October, 2005.

4. Tocci, Lisa: “Torque Spark.”
Lubes ‘N’ Greases, September 2007.

5. Mitchell Repair Information Company, LLC.

6. Motor Information Systems
Check Chart 2007 Quick Lubrication Guide.
AMSOIL oils, fluids, filters and fuel additives for cars, trucks, snowmobiles, marine watercraft, farming, construction, offroad and racing applications

If you want to buy AMSOIL Products, visit our vehicle maintenance page, or the AMSOIL On-Line Store or download a clickable pdf e-catalog

Additional and Special Resources:

Gear Lube Comparison Research
This “white paper” gives extensive certified performance data using all of the definitive ASTM tests – with shocking results that explain why so many differentials fail in 3/4 and 1-ton pickups, as well as larger GVWR fleet trucks.
Lessons from the Million Mile Van



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UltimateSyntheticOil promotes the AMSOIL Filtration and Lubrication Gold Standards in the United States and Canada If you want to buy AMSOIL Products, visit our vehicle maintenance page, or the AMSOIL On-Line Store or download a clickable pdf e-catalog