Transmission and Drivetrain: Description and Operation

The source of the drivetrain's power is generated by the engine and delivered to the transmission. The driveline transfers the engine torque through the driveshaft to the axle.
^ On 2-wheel drive vehicles, power is transmitted through the transmission to the driveshaft and then to the rear axle.
^ On 4-wheel drive vehicles, power is transmitted through the transmission and the transfer case. The transfer case directs the power to the rear driveshaft and then to the rear axle. When engaged, it also transmits power through the front driveshaft to the front axle.
There are three types of driveshafts used:
^ One-piece rear driveshaft with two U-joints and a front slip yoke.
^ Two-piece rear driveshaft with three U-joints, a front coupling shaft, a center bearing and a rear driveshaft.
^ One-piece front driveshaft with two U-joints and a slip yoke.
The rear driveshaft is connected to the output shaft of the transmission or transfer case and to the rear axle. The front driveshaft is connected to the transfer case and to the front axle. Universal joints are used at both ends of the driveshaft to allow for angular motions. Slip yokes are used to allow for any changes to the length of the driveshaft. The engine torque enters the axle through the drive pinion, which rotates the ring gear. The ring gear is mounted to the differential case, which contains the gears that transmit power to the rear axle shafts or front halfshafts. These shafts rotate the drive wheels.
The engine angle is built into the engine mounts. If the engine angle is out of specification, the engine mounts must be inspected for damage.





The Vehicle Certification (VC) label is located in the driver doorjamb. The first two digits of the axle code indicate the rear axle and the third digit refers to the front axle, if so equipped.