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Limited slip differentials, developed over 40 years ago to counter drive wheel slippage when different traction conditions exist on either side of an axle, are still widely employed by the automotive industry to improve driving control. In a limited slip differential (LSD) frictional couplings connect the axle shafts to the differential and provide the means of transmitting power to the wheels. The friction plates in the coupling may contain a variety of friction materials including metal, paper, sintered bronze, and carbon. Each one of these materials has very different frictional and wear characteristics and each one requires a different response from the gear additive package. Each plate must be durable over the course of the vehicle lifetime irrespective of the material used.

Limited slip differentials have been used for many years in the automotive industry to improve driving control and reduce chatter and vibrations from the rear axle. The choice of proper lubricant is essential to quiet and smooth operation. Special additives are available to modify the frictional response in the coupling to eliminate stick-slip problems. In recent years, there has been a trend in the US toward higher axle sump temperatures. Therefore, new limited slip additives are needed with better thermal stability and frictional performance. In this paper, we will present the results of the development of a bench test to measure the friction performance of limited slip lubricants.