Differential Assembly: Description and Operation

The front axle on four-wheel drive model vehicles has a central disconnect feature that, under most conditions, allows shifting into and out of four-wheel drive when the vehicle is in motion. It is engaged by an electronically-activated thermal actuator.

The thermal actuator contains a coil, fluid, and a plunger. When the coil is heated, the liquid changes to a gas and extends the plunger, which engages the front axle. To disengage, the gas must cool to a liquid.

The axle uses a conventional ring and pinion gear set to transmit the driving force of the engine to the wheels. The differential allows the wheels to turn at different rates of speed while the axle continues to transmit the driving force. This prevents tire scuffing when going around corners and premature wear on internal axle parts. The ring and pinion set and the differential are contained within an aluminum carrier. The axle identification number is located on a tag attached to the right axle tube.

The drive axles (halfshafts) are completely flexible assemblies consisting of inner and outer constant velocity (CV) joints protected by thermoplastic boots and connected by an axle shaft (output shaft).