AMSOIL SEVERE GEAR® 75W-140 100% SYNTHETIC GEAR LUBE

AMSOIL SEVERE GEAR 75W-140 100% Synthetic Gear Lube delivers heavy-duty protection for differentials, manual transmissions and transfer cases operating under the most punishing conditions. It is built for trucks towing heavy trailers, equipment working long hours in extreme heat, and any drivetrain where standard gear oil simply cannot keep up.

Modern pickups, SUVs and heavy equipment generate enormous torque loads in the differential. Towing a fifth wheel up a mountain grade, hauling a loaded flatbed trailer in summer heat, or running a piece of off-road equipment for hours at a time pushes gear oil to its limits. When conventional gear lube loses viscosity or breaks down under that stress, metal-to-metal contact, accelerated wear and even catastrophic failure can follow.

CONTROLS THERMAL RUNAWAY
Thermal runaway occurs when a gear lubricant can no longer control friction under high-stress conditions. Rising heat thins the oil further, which increases friction, which generates more heat, creating a destructive feedback loop. AMSOIL SEVERE GEAR 75W-140 synthetic gear lube is formulated to break that cycle. It maintains its viscosity under extreme heat and high-load operation, keeping differential temperatures in check during heavy towing and steep-grade driving. With a flash point of 213°C (415°F), it resists thermal breakdown where conventional 75W-140 gear oils fall short.

IRON-SULFIDE BARRIER COATING FOR EXTREME WEAR PROTECTION
Ring-and-pinion gears and bearings in differentials are subjected to tremendous sliding and rolling contact forces, especially in trucks like the Ram 2500, Ford F-250, Chevy Silverado 2500HD and other heavy-duty pickups used for towing and hauling. AMSOIL SEVERE GEAR contains proprietary additives that form an iron-sulfide barrier coating directly on gear surfaces. This coating acts as a sacrificial protective layer against wear, pitting and scoring, providing protection that goes beyond what standard extreme-pressure additives can deliver.

EXCELS IN TEMPERATURE EXTREMES
The 75W-140 viscosity grade must perform across a wide operating range, from cold startup to sustained high-temperature operation. AMSOIL SEVERE GEAR 75W-140 has a Brookfield viscosity of 107,000 cP at -40°C (ASTM D2983), keeping it within the critical pumpability threshold for cold-weather startups. Its wax-free synthetic construction improves cold-flow properties compared to conventional gear oils, reducing drag on the drivetrain and improving cold-weather shifting in manual transmissions. On the high end, a kinematic viscosity of 27.5 cSt at 100°C (ASTM D445) and a viscosity index of 153 mean the oil maintains a thick, protective film even at sustained high operating temperatures. This combination makes it a strong choice as a synthetic 75W-140 gear oil for towing in both summer heat and winter cold.

BUILT-IN LIMITED-SLIP COMPATIBILITY
SEVERE GEAR 75W-140 contains friction modifiers for limited-slip differential applications. This eliminates the chatter and noise that can develop in limited-slip diffs when using gear oil without the proper friction-modifying chemistry. For applications that require additional limited-slip friction modifier beyond what is included, AMSOIL Slip Lock can be added. This makes SEVERE GEAR a direct fit for limited-slip differentials in Ford, GM and Ram trucks without needing a separate additive purchase in most cases.

RUST, CORROSION AND FOAM RESISTANCE
Gear housings can accumulate moisture from condensation, especially in vehicles that sit between uses or operate in humid climates. SEVERE GEAR protects against rust and corrosion to preserve gear surfaces and bearings during both operation and storage. It also demonstrates excellent foam stability (ASTM D892), with Sequence I and III results of 0/0 mL and Sequence II at 20/0 mL, preventing aeration that would compromise film strength under load. Copper corrosion testing (ASTM D130) rates 1b at 121°C over 3 hours, confirming compatibility with copper-alloy synchronizers and bushings.

SPECIFICATIONS AND COMPATIBILITY
AMSOIL SEVERE GEAR 75W-140 meets API GL-5, MT-1, MIL-PRF-2105E, Dana SHAES 234 (formerly Eaton PS-037) and Mack GO-J specifications. It can also be used in axles where an API GL-4 lubricant is recommended. It is compatible with other GL-5 specifications from Ford, GM and Chrysler. SEVERE GEAR is compatible with conventional and synthetic gear oils, though mixing with other oils will shorten oil life and reduce 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.

SERVICE LIFE
For differentials in cars, SUVs and light trucks, SEVERE GEAR 75W-140 supports drain intervals of up to 100,000 miles (161,000 km) in normal service and 50,000 miles (80,500 km) in severe service, or according to the owner's manual, whichever is longer. For heavy-duty Class 8 line haul applications, follow the OEM drain interval for synthetic oil up to 250,000 miles (402,500 km) or three years. Vocational and delivery applications are supported up to 120,000 miles (193,200 km) or three years. Heavy-duty off-road applications are supported up to 100,000 miles or two years. For non-differential applications such as manual transmissions and transfer cases, consult the owner's manual or OEM for normal or severe synthetic oil service intervals. Where no OEM interval is available, drain at twice the interval specified for conventional oil. More frequent changes are recommended in dusty or dirty conditions unless the gear system is properly sealed with membrane-type breathers. Extended drain intervals are not supported where water contamination occurs.