Limited Slip Wet Clutch Transmission Fluid for AWD Differentials; Part 1: System Requirements and Evaluation Methods

Part 1 of this paper is focused on requirements and evaluation methods for transmission fluids used to lubricate wet clutches in all-wheel drive systems. Part 2: Fluid Development and Verification; presents more measurement data and shows how these results are used in the fluid development process.

The investigated all-wheel drive system, featuring a wet multi-plate clutch with a sintered brass base friction material, is described with emphasis on the demands placed on the transmission fluid.

A new test equipment to determine the frictional (μ-V) characteristics of the transmission fluid is described. The equipment can measure the actual temperature experienced by the fluid in the contact zone using an infrared temperature measurement method, as well as temperature in the oil sump and inside the clutch discs by use of thermocouples. Variable operation parameters include velocity, normal force and oil flow.