1 Pinion gear (6 off) 2 Side gear (front propshaft drive) 3 Side gear (rear propshaft drive) 4 Cover plate 5 Housing/ring gear 6 Friction thrust washer 7 Thrust washer 8 Roller bearing The Torsen® unit comprises a housing, two side gears, six pinion gears, thrust and friction washers and a cover plate. The housing is a machined casting which contains all the differential components. Six machined pockets accept the pinion gears. The base of each pocket has a cast recess which retains oil to lubricate the pinion gear ends. The closed end of the housing has a roller bearing pressed into a hole. The transfer box main shaft is located through the bearing which provides support between the housing and the shaft. The main shaft has cross drillings which supply lubricating oil from the oil pump to the internal components of the differential. Three threaded holes are located equally around the open end of the housing and provide for the attachment of the cover plate with bolts. The outer circumference of the housing has cast and machined teeth which mesh with corresponding teeth in the transfer box synchroniser sleeve. Rotational input from the transmission is passed, via the transfer box input shaft, directly to the synchroniser sleeve for high range or indirectly to the synchroniser sleeve via the planetary gear set for low range. The teeth on the housing allow for the sliding motion of the synchroniser sleeve when the transfer box range is changed. The pinion gears are parallel, helical gears which locate in the machined pockets in the housing. The lands of the helical teeth are ground with a radius which matches the internal diameter of the housing pockets. This creates frictional forces between the pinion gears and the housing and contributes to the operation of the unit. Each pinion gear has a machined section with no teeth. The pinions are fitted in the housing in opposite pairs. When fitted, one pinion gear of each pair meshes with one of the side gears, with the machined section of that gear preventing meshing with the other side gear.