Modern differentials handle more heat and stress than ever before. AMSOIL SEVERE GEAR® Synthetic Gear Lube protects against the devastating effects of high-heat, severe-service operation.

Picture of 75w90, 75w110, and 75w140 quart packaging options.

Your vehicle’s differential is likely not top of mind while hauling snowmobiles or ATVs for a fun weekend on the trails. Unfortunately, towing is in the severe service category and places extreme stress on your drive-train. Today’s vehicles produce substantially more horsepower, torque and towing capacity than their predecessors, yet the design of differential gears and bearings remains largely unchanged. Many differentials even use less gear lube and lower viscosities than before in an effort to reduce drag and increase fuel economy. In essence, less gear lube is responsible for providing more protection.

Fighting the Grind

Differential designs have inherent weaknesses. In a traditional automotive differential, the pinion gear concentrates intense pressure on the ring gear. As the gear teeth mesh, they slide against one another, separated only by a thin layer of lubricant. The repeated stress the lubricant film bears can shear gear lubes, causing permanent viscosity loss. Once sheared, the fluid film weakens, ruptures and allows metal-to-metal contact, eventually leading to gear and bearing failure. The situation is amplified by severe-service applications like towing.

Thermal Runaway

Diagram showing Thermal Runaway.

The extreme pressures and temperatures placed on gear lubricants can lead to a serious issue called thermal runaway. As temperatures in the differential climb, some gear lubes lose viscosity and load-carrying capacity. When extreme loads break the lubricant film, metal-to-metal contact occurs, increasing friction and heat. This increased friction and heat, in turn, results in further viscosity loss, which further increases friction and heat. As heat continues to spiral upward, viscosity continues to spiral downward. Thermal runaway is a vicious cycle that leads to irreparable equipment damage from extreme wear, and ultimately catastrophic gear and bearing failure.

AMSOIL SEVERE GEAR Synthetic Gear Lube

SEVERE GEAR excels in protecting gears and bearings from the rigors of severe-service operation. 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 performance.

  • Superior film strength
  • Controls thermal runaway
  • Protects against rust and corrosion
  • Helps reduce operating temperatures
  • Maximum efficiency
  • Long oil, seal and equipment life
  • Flexible easy-pack for clean, fast installation
Cutaway view of differential

Follow your vehicle owner’s manual recommendations for initial (break-in) gear oil change. (Most manufacturers recommend an initial gear lube change at or before 5,000 miles.)  Consult the AMSOIL Product Guide to find the proper viscosity for your vehicle.

Vehicle with trailer and ATVs.

The above article is taken from the December 2018 issue of the AMSOIL Dealer Magazine.

Chart comparing the Brookfield Viscosity @-40C (ASTM D2983) of AMSOIL Severe Gear, Valvoline SynPower and Mobil 1 75w40 viscosity gear lubes.

75w140 Synthetic Gear Lube is the required lubricant in most heavy duty pickups and many larger trucks used for towing or hauling heavy loads.

The above chart shows the results of the ASTM D2983 test to determine the low temperature viscosity of a lubricant, in this case, gear lubricant at -40 degrees C. The lower the Bar, the better the lubricant flows when cold. In this test the AMSOIL 75w140 Severe Gear provided 20% more cold temperature protection than the standard requires while the Mobil 1 75w140 failed to meet the standard.

Samples were sent blind to eliminate bias to an independent testing facility in May 2018.

The above chart was taken from the March 2019 AMSOIL Magazine, Dealer Edition

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