Section 133 (Drive Shafts): Description
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 drive shaft to the axle. On 2WD vehicles, power is transmitted through the transmission to the drive shaft and then to the rear axle. On 4WD vehicles, power is transmitted through the transmission and the transfer case. The transfer case directs the power to the rear drive shaft and then to the rear axle. When engaged, it also transmits power through the front drive shaft to the front axle. On All Wheel Drive (AWD), vehicles, power is transmitted through the transmission and continuously proportioned to the front and rear axles through the transfer case.
The universal joints are a lubed-for-life design and require no lubrication. Universal joints are equipped with nylon thrust washers, located at each base of the bearing cup, which control end play, position the needle bearing and improve grease movement. See Fig 1 .
The rear drive shaft is connected to the output shaft of the transmission or transfer case and to the rear axle. The front drive shaft is connected to the transfer case and to the front axle. Universal joints and CV joints are used at both ends of the drive shaft to allow for angular motions. Slip yokes are used to allow for any changes to the length of the drive shaft. 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.
Vehicles have the following types of drive shafts:
- One-piece rear drive shaft with 2 "U" joints and a front slip yoke.
- Quasi one-piece rear drive shaft with a splined shaft at one end and a yoke on the other (4-wheel drive Explorer Sport and Sport-Trac).
- Two-piece rear drive shaft with 3 "U" joints, a front coupling shaft, a center bearing and a rear drive shaft (Ranger).
- Front drive shaft with one front "U" joint, a slip yoke and a rear CV joint.