has the best Synthetic Gear Lubes available like the AMSOIL Severe Gear® Gear Lube for your differential which Offers Superior Gear and Bearing Protection.

Differentials are very costly to repair on vehicles, yet; usually relatively simple to change their fluid and inexpensive to service.  However, differentials sometimes can be the decision maker when it’s decided to get rid of a problem vehicle when it’s the “only” problem of the vehicle.   That’s why it’s Wise to use a high quality Synthetic Gear Lube like AMSOIL Severe Gear® Gear Lube in your differential; to prevent costly differential problems and repairs.

ORDER AMSOIL Severe Gear® Gear Lube NOW

AMSOIL Severe Gear® Synthetic Extreme Pressure (EP) Gear Lube is a premium-grade gear oil specifically engineered for maximum performance in severe-duty applications. This state-of-the-art AMSOIL formulation features an exclusive blend of high-viscosity, shear-stable synthetic base oils and an extra treatment of high-performance additives. AMSOIL Severe Gear Synthetic EP Gear Lube maintains its viscosity for long-lasting protection against metal-to-metal contact. The proprietary AMSOIL additives form an iron-sulfide barrier coating on gear surfaces, providing the ultimate line of defense against wear, pitting and scoring. AMSOIL Severe Gear helps prevent “thermal runaway” — a phenomenon caused by a lubricant’s inability to control friction and increased heat under high-stress conditions. By controlling thermal runaway, AMSOIL Severe Gear Synthetic EP Gear Lube inhibits rapid lubricant degradation and component damage. Equipment runs better and lasts longer with AMSOIL Severe Gear Synthetic EP Gear Lube.

Severe Gear Lineup Picture


AMSOIL Severe Gear provides performance beyond that possible with conventional gear oil. This AMSOIL custom product offers superior gear and bearing protection, better friction and heat reduction, increased efficiency and extended service life.

Temperature Extremes

AMSOIL Severe Gear EP Gear Lube excels in hot and cold temperature extremes. By design, it resists breakdown from high heat, preventing acids and carbon/varnish formation. Its wax-free construction also improves cold-flow properties, improving fuel economy and cold-weather shifting.


AMSOIL Severe Gear Synthetic EP Gear Lube is excellent for severe applications, such as towing, hauling, steep-hill driving, commercial use, plowing, racing, off-road use, rapid acceleration, frequent stop-and-go operation and high ambient temperatures. Higher horsepower, towing and hauling capabilities of modern vehicles make turbo-diesel pick-ups, SUVs, vans and delivery/utility vehicles especially prone to severe service. Other severe-duty vehicles include light, medium and heavy-duty trucks, buses, heavy equipment, 4X4s, tow trucks, race cars, tractors and motor homes.

Performance Features

  • Superior Film Strength
  • Controls Thermal Runaway
  • Rust and Corrosion Protection
  • Reduced Operating Temperatures
  • Improved Efficiency
  • Longer Oil, Seal, & Equipment Life


Click Here to review/download the AMSOIL Severe Gear Data Sheet.

Extends Drain Intervals

AMSOIL Severe Gear® is a stable formulation that lasts longer in service than conventional gear lubes. It maintains its viscosity, friction and lubricating properties for extended periods of time, even under severe conditions. AMSOIL Severe Gear® maximizes differential performance and service life while reducing maintenance costs through longer drain intervals and preventing costly repairs. Amsoil Severe Gear® is recommended for change intervals up to 100,000 miles in normal usage, or 50,000 miles in “severe” use.

Recommended for use in differentials, manual transmissions and other gear applications requiring any of the following specifications: API GL-5, MT-1, MIL-PRF-2105E, Dana SHAES 234 (Formerly Eaton PS-037), Mack GO-J, or the differential (hypoid) gear oil specifications from all domestic and foreign manufacturers such as GM, Ford and Daimler Chrysler. Can also be used in axles where an API GL-4 lubricant is recommended.

AMSOIL Severe Gear (75W-90) provides superior performance and replaces competitors’ 75W-90 and 80W-90 gear oils. It delivers the best fuel efficiency and cold-temperature performance of the Severe Gear oils.

AMSOIL Severe Gear (75W-110) provides superior performance and replaces competitors’ 75W-110, 75W-90 and 80W-90 gear oils. It delivers better viscosity protection than Severe Gear 75W-90 and better fuel efficiency than Severe Gear 75W-140. Use 75W-140 where required by OEM.

AMSOIL Severe Gear (75W-140) provides superior performance and replaces competitors’ 75W-140, 80W-140 and 85W-140 gear oils. Use where these viscosities are required by OEMs and where maximum viscosity protection is needed for extreme severe-duty applications.

AMSOIL Severe Gear is compatible with conventional and synthetic gear oils. Mixing AMSOIL gear oil with other oils, however, will shorten the oil life expectancy and reduce the performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed.

Aftermarket oil additives, other than those specified by AMSOIL, are not recommended for use with AMSOIL gear oil.

AMSOIL Severe Gear is compatible with most limited-slip differentials. If limited-slip differential chatter occurs, add AMSOIL Slip-Lock™ friction modifier additive.

Which Fluid?

Not for sure which weight of Differential Fluid is correct for your vehicle?  Click here and use the AMSOIL online application guide to determine correct gear lube. The online application guide has links to take you to the gear lube page for ordering.  It also has links for Synthetic Motor Oil & Filter for your car or you can go directly to the online store to order.

Our online catalog is available for you to view the entire AMSOIL line of products and use the “buy online” buttons right within the catalog.

Guaranteed by AMSOIL.

Amsoil as a warranty for all their products as proof that they stand behind their products.  Read about their warranty here.

Is it safe to switch to Synthetic Gear Lube?

Absolutely it is safe.  You can switch your vehicle to AMSOIL Synthetic Severe Gear® Lube at any time. Synthetic Gear Lube is completely compatible with conventional gear lubes.  However, if you have a limited-slip (or positraction) or a locking differential; then you should add Slip Lock  Oil Additive.

Helpful Links with best practices when servicing differential gear boxes.


Don’t want to change your own fluid?

You can buy your fluid and have your mechanic, independent shop or quick-lube change it for you.  Most quick-lubes, machanic shops and even dealerships will let you bring your own lubricant to them to insall.  If they will not allow you to bring your own, then find another shop that wants your business!

Video on Changing differential fluid in a 2006 Ford Expedition

AMSOIL Severe Gear® Gear Lube Line Receives Upgraded Technology

AMSOIL is continually researching methods to enhance its already-superior product line. New additive technology has recently been incorporated into the Severe Gear Synthetic EP Gear Lube line, providing even greater protection and performance. While users may notice the fluid color has changed slightly, the previous and new formulations are compatible and may be mixed. Pricing remains unchanged, providing even greater value.

In 2007, AMSOIL subjected Severe Gear 75W-90 Synthetic Gear Lube and a number of competing gear lubes to a comprehensive series of industry-standard tests. While some lubes performed well in some areas and poorly in others, Severe Gear placed near the top in all performance categories. It revealed itself to be the most well-balanced formula for its time, capable of providing exceptional performance and protection in a range of applications.

Since then, AMSOIL gear lube technology has advanced, making an already superior product stronger. As the results show, the new additive technology allows Severe Gear to outperform the previous formulation and all of its competitors as tested in 2007. AMSOIL has raised the bar for gear lube performance even higher.

Increased Extreme-Pressure Protection

High-horsepower / high-torque applications demand lubricants with increased extreme-pressure (EP) properties. The Falex Extreme-Pressure Test (ASTM D-3233) is used to determine a lube’s ability to provide EP Protection. As Chart 1 shows, although the previous formulation ranked in the top tier, the new technology provides an 80 percent increase in EP protection and easily outperforms all competing formulations from A Study of Automotive Gear Oils.

Increased Wear Protection

Severe applications such as towing, hauling and racing subject gear lubes to severe conditions, causing fluid film rupture in lesser lubricants. Metal-to-metal contact can result, inviting rapid wear and, ultimately, gear failure.

The 4-Ball Load Wear Index Test (ASTM D-2783) determines a gear lube’s anti-wear properties under heavy load. Higher values, reported as the Load Wear Inder (LWI), indicate increased wear resistance.

As demonstrated in Chart 2, the new formulation provides a 14 percent higher value than the previous formulation and ranks higher than all scores achieved in 2007 testing.

The technology behind the entire line of Sever Gear Synthetic EP Gear Lubes also provides increased foam control, thermal and oxidative stability, limited-slip differential chatter suppression and torque retention.

Chart 1 Falex-Extreme Pressure Test

Chart 2 4-Ball EP Load Wear Index Test

AMSOIL Severe Gear Synthetic Gear Lube


AMSOIL Severe Gear® Gear Lube maybe used in Harley Davidson Motorcycles

AMSOIL has several Synthetic Lubricants which can be used in Harley-Davidson Models. For example, Severe Gear (SVO) 75W-140 can be used for Harley-Davidson Part # 99892-84 Transmission Lube.

AMSOIL has Products for the following Harley-Davidson Part Numbers:

  • 99816-60 HF Engine Oil
  • 99851-05 Formula
  • 99824-03 Screamin Eagle Syn 3
  • 99887-84 Primary Lube
  • 99892-84 Transmission Lube
  • 99896-88 Sport-Trans fluid
  • 99880-73 Type B fork oil
  • 99884-80 Type E fork oil

Click here to see the FULL AMSOIL Recommended Lubricants for Harley-Davidson Motorcycles.

TSB: SE-2004-10-1 – AMSOIL Synthetic Motorcycle Oils, Gear Lubes and Suspension Fluids

Except from TSB: SE-2004-10-1
Harley-Davidson recommends SAE 60 or SAE 50 engine oil for Flathead, Knucklehead, Panhead and Shovelhead equipped bikes. AMSOIL recommends AMSOIL SAE 60 Synthetic Motorcycle Oil (MCS) or 20W-50 Synthetic Motorcycle Oil (MCV) for these vintage models, while AMSOIL MCS or 75W-140 Severe Gear® Synthetic Gear Lube (SVO) is recommended in the transmissions. Shovelhead is the only model with a chaincase that is lubricated with engine oil.

So, treat your Hog to the best lubricants available.  Quote from a local Harley customer, “AMSOIL is like ‘The Mystery Oil’ as it’s best kept secret oil” and “I only put the best in my Harley, so I use Ams oil”.