Drive/Propeller Shafts, Bearings and Joints: Description and Operation

Driveline System
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.

The rear driveshaft is connected to the output shaft of the transmission and to the rear axle. The front driveshaft is connected to the transfer case and to the front axle. Universal joints are used at the 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.

Vehicles have the following types of driveshafts:
^ One-piece rear driveshaft with 2 U-joints and a front slip-yoke
^ Two-piece rear driveshaft with 3 U-joints, a front slip yoke and a center bearing with a slip yoke between the U-Joints on the rear shaft
^ One-piece front driveshaft with 2 U-joints, a slip-yoke and 2 U-joint flanges

The rear axle assemblies have the following features:
^ An integral type housing hypoid gear design
^ The hypoid differential ring gear and pinion consists of a ring gear and an overhung drive pinion that is supported by 2 opposed tapered roller bearings.
^ Pinion bearing preload, which is maintained by a collapsible spacer on the pinion shaft and adjusted by the pinion nut.
^ The axle housing assembly consists of a cast center section with 2 steel tube assemblies and a stamped differential housing cover.
^ The axle housing cover uses silicone sealant as a gasket.
^ The differential pinion shaft is retained by a differential pinion shaft lock bolt assembled to the differential case.
^ The differential case is mounted between 2 opposing differential bearings that are retained in the axle housing by removable bearing caps.
^ Use SAE 75W-140 High Performance Rear Axle Lubricant.
^ Use Additive Friction Modifier in Traction-Lok axles.
^ Differential bearing preload and ring gear backlash are adjusted by differential bearing shims located between the differential bearing caps and the rear axle housing.
^ The limited-slip differential contains differential clutch packs.

The Traction-Lok(R) rear axle assembly, except for the differential case and its internal components, is identical to the conventional rear axle. The Traction-Lok employs 2 multi-disc differential clutch packs to control differential action. The mounting distance of the differential side gear is controlled by plates on each side, friction and steel. Also included is a steel selective shim to control the position of the differential side gear, and a spring provides initial preload to the clutch pack. The steel clutch plates are splined to the axle shafts. The friction plates are contained in the case by matching slots, thus providing continuous engagement of the differential clutch packs.

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.

Vehicle Certification (VC) Label Example:

The vehicle certification (VC) label is located in the driver doorjamb. The first 2 digits of the axle code indicate the rear axle and the third digit refers to the front axle, if so equipped.

Front Axle Identification Tag:

Rear Axle Identification Tag (Part 1):

Rear Axle Identification Tag (Part 2):

Axle Identification Tag Denoting Interchangeability Affected Internally:

CAUTION: The axle identification tag is the official service identifier. Do not damage the tag. Always reinstall the tag after removing it for axle inspection/repair.

The axle identification tag identifies a particular axle design, a specific ratio, and if it is a conventional or limited slip (Traction-Lok) type. In addition, the plant code will not change as long as that particular axle assembly never undergoes an external design change. If, however, an internal design change takes place during the production life of the axle and that internal change affects components interchangeability, a dash and numerical suffix is added to the plant code. This means that as an assembly both axles are interchangeable; however, internally they are different. Therefore, each requires different internal components at the time of repair.