Differential. Description and Operation
Differential, Disassembled View
| Item | Description |
| 1 | Differential Case |
| 2 | Pinion Shaft |
| 3 | Gears |
| 4 | Side Gears |
Differential, Sectional View and External Seal
| Item | Description |
| 1 | Left Axle Shaft Seal |
| 2 | FWD (Front-Wheel Drive) Right Axle Seal |
| 3 | AWD (All-Wheel Drive) Right Axle Seal |
| 4 | Power Transfer Unit (PTU) Input Shaft Seal Surface |
Differential
The differential allows the axle shafts and wheels to rotate at different speeds during turns and transmits power to the Power Transfer Unit (PTU) on all-wheel drive vehicles.
The differential assembly consists of the following components:
- Differential Case (part of Final Drive Case)
- Two Pinion Gears supported by the pinion shaft
- Two Side Gears supported by the differential case and axle shafts
When driving straight, both front wheels rotate at approximately the same speed. This means both side gears rotate at the same speed, and the pinion gears do not rotate on the pinion shaft relative to the side gears. When the vehicle goes around a turn, the outside wheel is forced to rotate faster than the inside wheel. The side gears must now rotate at different speeds, and the pinion gears rotate on the pinion shaft, allowing the drive axles to rotate at different speeds while maintaining output torque.
Test yourself
A quick Ford Fusion quiz: every answer comes with an explanation and a link to the manual page.