GM Full-Size Trucks 1980-1987 Repair Guide

Rear Driveshaft

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REMOVAL & INSTALLATION



See Figures 1, 2 and 3

  1. Jack up your truck and support it with jackstands.
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  3. Scribe alignment marks on the driveshaft and flange of the rear axle, and transfer case or transmission. If the truck is equipped with a two piece driveshaft, be certain to also scribe marks at the center joint near the splined connection. When reinstalling driveshafts, it is necessary to place the shafts in the same position from which they were removed. Failure to reinstall the driveshaft properly will cause driveline vibrations and reduced component life.
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  5. Disconnect the rear universal joint by removing U-bolts or straps. Tape the bearings into place to avoid losing them.
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Fig. Fig. 1: Rear driveshaft U-bolt attachment



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Fig. Fig. 2: Rear driveshaft strap attachment

  1. If there are U-bolts or straps at the front end of the shaft, remove them. Tape the bearings into place. For trucks with two piece shafts, remove the bolts retaining the bearing support to the frame crossmember. Compress the shaft slightly and remove it.
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  3. If there are no fasteners at the front end of the transmission, there will only be a splined fitting. Slide the shaft forward slightly to disengage the axle flange, lower the rear end of the shaft, then pull it back out of the transmission. Most two wheel drive trucks are of this type. For trucks with two piece driveshafts, remove the bolts retaining the bearing support to the frame crossmember.
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Click image to see an enlarged view

Fig. Fig. 3: A box wrench may be used to loosen the U-joint strap retainers

  1. Reverse the procedure for installation. It may be tricky to get the scribed alignment marks to match up on trucks with two piece driveshafts. For those models only, the following instructions may be of some help. First, slide the grease cap and gasket onto the rear splines.
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On K models with 16 splines, after installing the front shaft to the transmission and bolting the support to the crossmember, arrange the front trunnion vertically and the second trunnion horizontally.
 
Models with 32 splines have an alignment key. The driveshaft cannot be replaced incorrectly. Simply match up the key with the keyway.
 

  1. On two wheel drive 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 edges, and carefully lubricating. A similar thump may be caused by the clutch plates in positraction 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.

 
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