A vehicle's differential transfers power from the engine to the drive wheels, using the difference in rotational speed of the inside and outside axles. An "open" differential allows the inside and outside wheels to turn at different speeds, but a limited slip or positraction differential is designed to deliver a more even amount of torque to each wheel, resulting in more controllable acceleration, less wheel-spin in turns and improved overall handling.

However, over time as the clutches in a limited-slip differential wear the differential can start to chatter, creating an annoying shudder that can only be eliminated by the use of a friction modifier. Friction modifiers work by lowering the lubricant's frictional properties, making the lubricant much slicker. This reduces the traction losses created by shear and churning (decreased viscosity).

AMSOIL synthetic gear lubes are limited-slip capable and do not require an additional friction modifier additive, but depending on the differential's friction material and degree of clutch wear chatter may still occur. The addition of AMSOIL Slip Lock eliminates chatter in mechanically sound differentials and is compatible with all petroleum and synthetic gear lubes.

When added to non-limited-slip API GL-5 gear oil a four ounce bottle of the Red Line differential friction modifier will significantly reduce break-in temperatures and frictional damage caused by shear conditions. This will improve the differential's ability to function in its intended manner under heavy loads. The additive can be used to prevent differential chatter in limited-slip or positraction units and also to break-in new differentials.