Driveshaft and universal joints — general information and inspection
General information
1. A driveshaft is a tube, or a pair of tubes, that transmits power between the transmission (or transfer case on 4WD models) and the differential. Universal joints are located at either end of the driveshaft and in the center on two-piece driveshafts.
2. Single piece driveshafts employ a splined yoke at the front, which slips into the extension housing of the transmission. This arrangement allows the driveshaft to slide back-and-forth within the transmission during vehicle operation to compensate for changes in length due to suspension movement. An oil seal prevents leakage of fluid at this point and keeps dirt from entering the transmission. If leakage is evident at the front of the driveshaft, replace the oil seal (see Automatic transmission).
3. If a two-piece driveshaft is used, a slip joint is employed on the front of the rear driveshaft section.
4. Two-piece driveshafts also have a center support bearing. The center bearing is a ball-type bearing mounted in a rubber cushion attached to a frame crossmember. The bearing is pre-lubricated and sealed at the factory.
5. On all models, the driveshaft assembly requires very little service. The universal joints are lubricated for life and must be replaced if problems develop. The driveshaft must be removed from the vehicle for this procedure.
6. Since the driveshaft is a balanced unit, it’s important that no undercoating, mud, etc., be allowed to stay on it. When the vehicle is raised for service it’s a good idea to clean the driveshaft and inspect it for any obvious damage. Also, make sure the small weights used to originally balance the driveshaft are in place and securely attached. Whenever the driveshaft is removed it must be reinstalled in the same relative position to preserve the balance.
7. Problems with the driveshaft are usually indicated by a noise or vibration while driving the vehicle. A road test should verify if the problem is the driveshaft or another component.
Inspection
8. Raise the rear of the vehicle and sup- port it securely on jack stands. Block the front wheels to keep the vehicle from rolling off the stands.
9. Crawl under the vehicle and visually inspect the driveshaft. Look for any dents or cracks in the tubing. If any are found, the driveshaft must be replaced.
10. Check for oil leakage at the front and rear of the driveshaft. Leakage where the driveshaft enters the transmission or transfer case indicates a defective transmission/transfer case seal (see Automatic transmission). Leakage where the driveshaft enters the differential indicates a defective pinion seal (see Pinion oil seal — replacement).
11. While under the vehicle, have an assistant rotate a rear wheel so the driveshaft will rotate. As it does, make sure the universal joints are operating properly without binding, noise or looseness. Listen for any noise from
the center bearing (if equipped), indicating it’s worn or damaged. Also check the rubber portion of the center bearing for cracking or separation, which will necessitate replacement.
12. The universal joint can also be checked with the driveshaft motionless, by gripping your hands on either side of the joint and attempting to twist the joint. Any movement at all in the joint is a sign of considerable wear. Lifting up on the shaft will also indicate movement in the universal joints.
13. Finally, check the driveshaft mounting bolts at the ends to make sure they’re tight.
14. On 4WD models, the above driveshaft checks should be repeated on the front driveshaft as well. In addition, check for leakage around the sleeve yoke, indicating failure of the yoke seal.
15. Check for leakage where the driveshafts connect to the transfer case and front differential. Leakage indicates worn oil seals.
16. At the same time, check for looseness in the joints of the front drive axles. Also check for grease or oil leakage from around the drive axles by inspecting the rubber boots and both ends of each axle. Oil leakage around the axle flanges indicates a defective axle-shaft oil seal. Grease leakage at the CV joint boots means a damaged rubber boot. For servicing of these components, see the appropriate Sections.