GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

Driveshaft and U-joints

Print

Full-size Buick, Pontiac and Oldsmobile driveshafts are of the conventional, open type. Located at either end of the driveshaft is a U-joint or universal joint, which allows the driveshaft to move up and down to match the motion of the rear axle. The front U-joint connects the driveshaft to a slip-jointed yoke. This yoke is internally splined, and allows the driveshaft to move in and out on the transmission splines. The rear U-joint is clamped or bolted to a companion flange fastened to the rear axle drive pinion. The rear U-joint is secured in the yoke in one of two ways. Dana and Cleveland design driveshafts use a conventional type snapring to hold each bearing cup in the yoke. The snapring fits into a groove located in each yoke end, just on top of the bearing cup. A Saginaw design driveshaft secures the U-joints differently. Nylon material is injected through a small hole in the yoke during manufacture, and flows along a circular groove between the U-joint and the yoke creating a non-metallic snapring.

There are two methods of attaching the rear U-joint to the rear axle. One method employs a pair of straps, while the other method is a set of bolted flanges. Bad U-joints, requiring replacement, will produce a clunking sound when the vehicle is put into gear and when the transmission shifts from gear to gear. This is due to worn needle bearings or a scored trunnion end possibly caused by improper lubrication during assembly. U-joints require no periodic maintenance and therefore have no lubrication fittings, except replaced U-joints.

Some driveshafts, generally those in heavy duty applications, use a damper as part of the slip joint. This vibration damper cannot be serviced separately from the slip joint. If either component goes bad, the two must be replaced as a unit.

REMOVAL & INSTALLATION



See Figures 1, 2 and 3

  1. Disconnect the negative (-) battery cable, raise the vehicle in the air and support it with jackstands.
  2.  
  3. Mark the relationship of the driveshaft to the differential flange so that they can be reassembled in the same position.
  4.  
  5. Disconnect the rear U-joint by removing the U-bolts or retaining straps.
  6.  
  7. To prevent the loss of the needle bearings, tape the bearing caps in place. If you are replacing the U-joint, this is not necessary.
  8.  
  9. Remove the driveshaft from the transmission by sliding it rearward. There will be some oil leakage from the rear of the transmission. It can be contained by placing a small plastic bag over the rear of the transmission and holding it in place with a rubber band.
  10.  
  11. To install the driveshaft, first inspect the outer diameter of the slip yoke to make sure it is not burred, or the transmission seal may be damaged. Apply automatic transmission fluid to all splined driveshaft yokes and then insert the driveshaft into the transmission. Don't force the shaft in. If you seem to be having trouble getting it to slip in, check alignment of the splines. If you're replacing the shaft, check for number and type of splines to make sure they are identical to the shaft you removed.
  12.  
  13. Before making the rear shaft connection, check the mating surfaces of the shaft and flange for nicks and burrs which could prevent proper seating of the shaft to the flange. Then, using the reference marks made earlier, align the driveshaft with the differential flange and secure it with the U-bolts or retaining straps. Make sure the bearings are aligned in the pinion flange yoke before installing bolts or bolts and straps. Torque bolt straps to 16 ft. lbs. (22 Nm).
  14.  



Click image to see an enlarged view

Fig. Fig. 1: Driveshaft assembly



Click image to see an enlarged view

Fig. Fig. 2: Driveshaft flange attachment



Click image to see an enlarged view

Fig. Fig. 3: Strap-type retainer on driveshaft

U-JOINT REPLACEMENT



See Figures 4, 5 and 6

NEVER clamp a driveshaft in a vise, as the tube is easily dented. Always clamp on one of the yokes, and support the shaft horizontally.

  1. Remove the driveshaft as explained above and remove the snaprings from the ends of the bearing cup.
  2.  


WARNING
The driveshaft is easily damaged using improper service methods. Use care not the dent or bend the driveshaft when removing the U-joints. If the bearing caps will not come loose, have a machine shop press them out.

  1. After removing the snaprings, place the driveshaft on the floor and place a large diameter socket under one of the bearing cups. Using a hammer and a drift, tap on the bearing opposite this one. This will push the trunnion through the yoke enough to force the bearing cup out of the yoke and into the socket. Repeat this procedure for the other bearing cups. If a hammer does not loosen the cups, they will have to be pressed out.
  2.  

A Saginaw design driveshaft secures its U-joints in a different manner than the conventional snaprings of the Dana and Cleveland designs. Nylon material is injected through a small hole in the yoke and flows along a circular groove between the U-joint and the yoke thus creating a synthetic snapring. Disassembly of this Saginaw type U-joint requires that the joint be pressed from the yoke. If a press is not available, it may be carefully hammered out using the same procedure as the Dana design although it may require more force to break the nylon ring. Either method, press or hammer, will damage the bearing cups and destroy the nylon rings. Replacement kits include new bearing cups and conventional metal snaprings to replace the original nylon type rings.

  1. Using solvent, thoroughly clean the entire U-joint assembly. Inspect for excessive wear in the yoke bores and on the four ends of the trunnion. The needle bearings should not be scored, broken, or loose in their cups. Bearing cups may suffer slight distortion during removal and should be replaced.
  2.  
  3. Pack the bearings with chassis lube (lithium base) and completely fill each trunnion end with the same lubricant.
  4.  
  5. Place new dust seals on trunnions with cavity of seal toward end of trunnion. Care must be taken to avoid distortion of the seal. A suitable size socket and a vise can be used to press on the seal.
  6.  
  7. Insert one bearing cup about 1 / 4 of the way into the yoke and place the trunnion into yoke and bearing cup. Install another bearing cup and press both cups in and install the snaprings. Snaprings on the Dana and Cleveland shafts must go on the outside of the yoke while the Saginaw shaft requires that rings go on the inside of the yoke. The gap in the Saginaw ring must face in toward the yoke. Once installed, the trunnion must move freely in yoke.
  8.  

The Saginaw shaft uses two different size bearing cups (the ones with the groove) fit into the driveshaft yoke.



Click image to see an enlarged view

Fig. Fig. 4: Partially inserted bearing cap



Click image to see an enlarged view

Fig. Fig. 5: Installing the retaining ring



Click image to see an enlarged view

Fig. Fig. 6: Tapping the yoke to seat the retaining ring

DRIVESHAFT BALANCING



See Figure 7

This service should only be performed if you have access to a proper lift or hoist.

  1. Place the car on a twin post hoist so that the rear of the car is supported on the rear axle housing and the rear wheels are free to rotate. Remove both the rear wheels and reinstall wheel lug nuts with the flat side next to the drum.
  2.  
  3. Mark and number the driveshaft at four points 90° apart at the rear of the shaft just forward of the balance weight.
  4.  
  5. Install two hose clamps on the rear of the shaft and slide them rearward until they stop at the nearest balance weight welded to the tube. Align both clamps to any one of the four marks and tighten them.
  6.  
  7. Run the car through the speed range of 50-55 mph (89 kph). Note the amount of imbalance.
  8.  


CAUTION
Never run the car higher than 55 mph (89 kph). Also, everyone should stay clear of the area to avoid possible injury. Do not run the car for long periods of time on the lift due to danger of overheating the engine or transmission.

  1. Loosen the clamps and rotate clamp heads 90° to the next mark on the shaft. Tighten the clamps and repeat Step 4.
  2.  
  3. Repeat Step 5 until the car has been run with clamps heads at all four marks on the shaft.
  4.  
  5. Position the clamps at the point of minimum imbalance. Rotate the clamp heads away from each other 45°. Run the car and note if imbalance has improved.
  6.  
  7. Continue to rotate the clamps apart at smaller angular increments until the balance is best.
  8.  
  9. Install the wheels and road test the car for a final check. Vibration felt on the lift may not show up on the road test. If the balance is not improved, replace the driveshaft.
  10.  



Click image to see an enlarged view

Fig. Fig. 7: Positioning the hose clamps to achieve best balance

 
label.common.footer.alt.autozoneLogo