GM Full Size Vans 1967-1986 Repair Guide

Driveshaft and U-Joints

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REMOVAL & INSTALLATION



See Figures 1, 2, 3, 4 and 5



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Fig. Fig. 1: Remove the straps retaining the driveshaft to the differential



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Fig. Fig. 2: View of a common rear driveshaft U-bolt attachment



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Fig. Fig. 3: View of a common rear driveshaft strap attachment



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Fig. Fig. 4: Common two-piece driveshaft mounting



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Fig. Fig. 5: Common two-piece driveshaft alignment

  1. Raise the vehicle and support it on jackstands. There is less chance of lubricant leakage from the rear of the transmission if the rear is raised.
  2.  
  3. Matchmark the driveshaft and rear pinion flange and both halves of 2-piece driveshaft. Remove the U-bolts or straps at the rear axle. Tape the bearing cups to the trunnions.
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  5. On models with 2-piece driveshaft, remove the bolts attaching the bearing support to the frame crossmember.
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  7. Slide the driveshaft forward and lower it. Slide the driveshaft toward the rear of the vehicle and disengage the splined sleeve from the output shaft of the transmission.
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  9. Remove the driveshaft from under the van.
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  11. Installation is the reverse of removal. Use the matchmarks made previously to help facilitate alignment. For models with 2-piece driveshaft, install the front half into the transmission and install the support to the crossmember. Rotate the shaft so that the front U-joint trunnions so that all are vertical. Rotate the rear shaft 4 splines to the left of the vehicle and connect the front and rear shaft. Some 2-piece driveshafts can only be assembled one way, in which case these instructions can be ignored. Attach the rear U-joint to the axle. On automatic transmission models, lubricate the internal yoke splines at the transmission end of the shaft with lithium base grease. The grease should seep out through the vent hole.
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A thump in the rear driveshaft sometimes occurs when releasing the brakes after braking to a stop, especially on a downgrade. This is most common with automatic transmission. It is often caused by the driveshaft splines binding and can be cured by removing the driveshaft, inspecting the splines for rough spots or sharp edges, and carefully lubricating. A similar noise may also be caused by the clutch plates in Positraction (through 1973) limited slip rear axles binding. If this isn't caused by wear, it can be cured by draining and refilling the rear axle with the special lubricant and adding Positraction additive, both of which are available from dealers.

U-JOINT OVERHAUL

U-Joint is mechanic's jargon for universal joint. U-joints should not be confused with U-bolts, which are U-shaped bolts used to hold U-joints in place to the axle or transfer case.

There are two types of U-joints used in these trucks. The first is held together by wire snaprings in the yokes. The second type, first used in 1975, is held together with injection molded plastic retainer rings. This type cannot be reassembled, once disassembled. Repair kits are available, however.

Snapring Type

See Figures 6, 7 and 8



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Fig. Fig. 6: Exploded view of the snapring type U-joint components



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Fig. Fig. 7: Installing the trunnion on the driveshaft yoke



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Fig. Fig. 8: Installing the snapring

These U-joints may be found on all model years.

  1. Remove the driveshaft(s) from the truck.
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  3. Support the lockrings from the yoke and remove the lubrication fitting.
  4.  
  5. Support the yoke in a bench vise. Never clamp the driveshaft tube.
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  7. Use a socket to press against one trunnion bearing to press the opposite bearing from the yoke.
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  9. Grasp the cap and work it out.
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  11. Support the other side of the yoke and press the other bearing cap from the yoke and remove as in Steps 4 and 5.
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  13. Remove the trunnion from the driveshaft yoke.
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  15. If equipped with a sliding sleeve, remove the trunnion bearings from the sleeve yoke in the same manner as above. Remove the seal retainer from the end of the sleeve and pull the seal and washer from the retainer.
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  17. Disassemble the other U-joint. Clean and check the condition of all parts. You can buy U-joint repair kits to replace all the wearing parts.
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To assemble:
  1. Repack the bearings with grease and replace the trunnion dust seals after any operation that requires disassembly of the U-joint. Be sure that the lubricant reservoir at the end of the trunnion is full of lubricant. Fill the reservoirs with lubricant from the bottom.
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  3. Install the trunnion into the driveshaft yoke and press the bearings into the yoke over the trunnion hubs as far as it will go.
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  5. Install the lockrings.
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  7. Hold the trunnion in one hand and tap the yoke slightly to seat the bearings against the lockrings.
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  9. Replace the driveshaft.
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Molded Retainer Type

This type is found only on some 1975 and later models. It is held together with injection molded plastic rings.

Don't disassemble these joints unless you have a repair kit. The factory installed joints cannot be reassembled.

  1. Remove the driveshaft.
  2.  
  3. Support the driveshaft in a horizontal position. Place the U-joint so that the lower ear of the shaft yoke is supported by a 1 1 / 8 in. (28mm) socket. Press the lower bearing cup of the yoke ear. This will shear the plastic retaining the lower bearing cup.
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Never clamp the driveshaft tubing in a vise.

  1. If the bearing cup is not completely removed, lift the cross, insert a spacer and press the cup completely out.
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  3. Rotate the driveshaft, shear the opposite plastic retainer, and press the other bearing cup out in the same manner.
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  5. Remove the cross from the yoke. Production U-joints cannot be reassembled. There are no bearing retainer grooves in the cups. Discard all parts that were removed and substitute those in the overhaul kit.
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  7. Remove the sheared plastic bearing retainer from the yoke. Drive a small pin or punch through the injection holes to aid in removal.
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  9. If the other U-joint is to be serviced, remove the bearing cups from the slip yoke in the manner previously described.
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  11. Be sure that the seals are installed on the service bearing cups to hold the needle bearings in place for handling. Grease the bearings if they aren't pregreased.
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To assemble:
  1. Install one bearing cup partway into one side of the yoke and turn this ear to the bottom.
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  3. Insert the cross into the yoke so that the trunnion seats freely in the bearing cup.
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  5. Install the opposite bearing cup partway. Be sure that both trunnions are started straight into the bearing cups.
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  7. Press against opposite bearing cups, working the cross constantly to be sure that it is free in the cups. If binding occurs, check the needle rollers to be sure that one needle has not become lodged under the end of the trunnion.
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  9. As soon as one bearing retainer groove is exposed, stop pressing and install the bearing retainer snapring.
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  11. Continue to press until the opposite bearing retainer can be installed. If difficulty installing the snaprings is encountered, rap the yoke with a hammer to spring the yoke ears slightly.
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  13. Assemble the other half of the U-joint in the same manner.
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  15. Check that the cross is free in the cups. If it is too tight, rap the yoke ears again to help seat the bearing retainers.
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  17. Replace the driveshaft.
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