Power and Mobility (P&M)

Development of a Laboratory Based Test Methodology to Identify Axle Lubricants with Limited Slip Capability

by Allen S. Comfort; Adam Brandt; Steven Thrush


Modern vehicles use various methods to improve traction. One way to control torque to the drive wheels and improve traction is the limited slip differential (LSD). These differentials prevent loss of traction in the event that a driving wheel loses grip. A popular arrangement is the clutch-type LSD. Clutch-type LSDs use alternating friction and reaction plates lubricated by gear oils with specific frictional properties that allow for smooth and quiet operation. It is essential that vehicles designed with LSDs use gear oils with the appropriate frictional characteristics, but each manufacturer relies on proprietary test methods to identify compatible gear oils for their LSDs. This lack of standardization limits the availability of compatible oils. To deal with this problem, the Army is developing a laboratory based test method using the SAE No. 2 friction test machine to identify fully formulated gear oils compatible with LSDs found in military equipment.