Main gear (Audi 100 C4)

The gearbox and final drive are located in the Audi-100, as in almost all front-wheel drive cars, in one common housing. Torque from the engine goes to the final drive through one small and one large gear. The differential housing is bolted to the large gear. This housing contains four meshing bevel gears, two of which are connected to the drive axle shafts.

As long as the car is moving straight ahead, both front wheels rotate at the speed of the large pinion of the main transmission. The bevel gears of the differential, which rotate at the same speed, on the contrary, are stationary. When going around a bend, the outer wheel must travel a longer distance than the one located inside the bend. Then the bevel gears start working: the faster rotation of the outer wheel and its bevel gear acts through both satellite bevel gears on the bevel gear on the inside of the bend, which correspondingly rotates more slowly. This alignment is necessary, otherwise the car would move jerkily on bends with slipping front wheels. The presence of a differential can also be a disadvantage if one of the drive wheels spins on a slippery surface. Then practically no traction is transmitted to the other front wheel, the car does not move from the spot.