Repair Pontiac Mid-size 1974-1983 Repair Guide

Axle Shaft and Bearings

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Fig. Fig. 1 Cross-section of an axle shaft and bearing assembly



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Fig. Fig. 2 Exploded view of a standard rear axle assembly



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Fig. Fig. 3 Exploded view of a conventional differential case assembly



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Fig. Fig. 4 Exploded view of a disc-type limited slip differential case assembly

Two types of axles are used on these models, the C and the non-C type. Axle shafts in the C type are retained by C-shaped locks, which fit grooves at the inner end of the shaft. Axle shafts in the non-C type are retained by the brake backing plate, which is bolted to the axle housing. Bearings in the C type axle consist of an outer race, bearing rollers, and a roller cage retained by snaprings. The non-C type axle uses a unit roller bearing (inner race, rollers, and outer race), which is pressed onto the shaft up to a shoulder. When servicing C or non-C type axles, it is imperative to determine the axle type before attempting any service. Before attempting any service to the drive axle or axle shafts, remove the axle carrier cover and visually determine if the axle shafts are retained by C-shaped locks at the inner end, or by the brake backing plate at the outer end.

REMOVAL & INSTALLATION



Non C-Type


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Fig. Fig. 5 Removing the axle shaft



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Fig. Fig. 6 Nick the bearing retainer using a chisel-non C-type rear axle

Design allows for maximum axle shaft end-play of 0.022 in., which can be measured with a dial indicator. If end-play is found to be excessive, the bearing should be replaced. Shimming the bearing is not recommended as this ignores end-play of the bearing itself and could result in improper seating of the bearing.

  1. Raise the vehicle, then remove the wheel, tire and brake drum.
  2.  
  3. Remove the nuts holding the retainer plate to the backing plate. Disconnect the brake line.
  4.  
  5. Remove the retainer and install nuts, finger-tight, to prevent the brake backing plate from being dislodged.
  6.  
  7. Pull out the axle shaft and bearing assembly, using a slide hammer.
  8.  
  9. Using a chisel, nick the bearing retainer in three or four places. The retainer does not have to be cut, merely collapsed sufficiently, to allow the bearing retainer to be slid from the shaft.
  10.  
  11. Press off the bearing and install the new one by pressing it into position.
  12.  
  13. Press on the new retainer.
  14.  

Do not attempt to press the bearing and the retainer on at the same time.

  1. Assemble the shaft and bearing in the housing being sure that the bearing is seated properly in the housing.
  2.  
  3. Install the retainer, drum, wheel and tire. Bleed the brakes.
  4.  

C-Type


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Fig. Fig. 7 Rear axle shaft C-lock and pinion shaft lockscrew locations



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Fig. Fig. 8 Installing the axle seal



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Fig. Fig. 9 Removing the axle bearing with a bearing puller



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Fig. Fig. 10 Installing the axle bearing



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Fig. Fig. 11 Before removing the differential cover, clean the dirt from around the bolts with a suitable brush



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Fig. Fig. 12 Remove the lower cover retaining bolts ...



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Fig. Fig. 13 ... then pry the cover away from the axle housing and allow the fluid to drain completely



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Fig. Fig. 14 Remove the remaining bolts, then take the cover off the rear axle housing assembly



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Fig. Fig. 15 Place a rag over the internal components, then carefully scrape off all the old gasket material



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Fig. Fig. 16 Loosen the pinion shaft lockscrew using a wrench



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Fig. Fig. 17 Remove the lockscrew (see arrow) so the pinion shaft may be withdrawn



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Fig. Fig. 18 Pull the pinion shaft from the differential in order to access the axle shaft C-lock



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Fig. Fig. 19 If the axle shaft is pushed inward, the C-lock may be removed from the groove



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Fig. Fig. 20 Carefully pull the axle shaft straight out to remove it



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Fig. Fig. 21 A prytool (or the end of the shaft) may be used to dislodge and remove the old bearing seal



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Fig. Fig. 22 Use a suitable tool to drive the new seal into position



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Fig. Fig. 23 Remove the drain plug, then fill the rear axle with lubricant

  1. Raise the vehicle and remove the wheels.
  2.  
  3. Remove the differential cover. Remove the differential pinion shaft lockscrew and the differential pinion shaft.
  4.  
  5. Push the flanged end of the axle shaft toward the center of the vehicle and remove the "C" lock from the end of the shaft.
  6.  
  7. Remove the axle shaft from the housing, being careful not to damage the oil seal.
  8.  
  9. Remove the oil seal by inserting the button end of the axle shaft behind the steel case of the oil seal. Pry the seal loose from the bore.
  10.  
  11. Seat the legs of the bearing puller behind the bearing. Seat a washer against the bearing and hold it in place with a nut. Use a slide hammer to pull the bearing.
  12.  
  13. Pack the cavity between the seal lips with wheel bearing lubricant and lubricate a new wheel bearing with same.
  14.  
  15. Use a suitable driver and install the bearing until it bottoms against the tube. Install the oil seal.
  16.  
  17. Slide the axle shaft into place. Be sure that the splines on the shaft do not damage the oil seal. Make sure that the splines engage the differential side gear.
  18.  
  19. Install the axle shaft C-lock on the inner end of the axle shaft and push the shaft outward so that the C-lock seats in the differential side gear counterbore.
  20.  
  21. Position the differential pinion shaft through the case and pinions, aligning the hole in the case with the hole for the lockscrew.
  22.  
  23. Use a new gasket and install the carrier cover. Be sure that the gasket surfaces are clean before installing the gasket and cover.
  24.  
  25. Fill the axle with lubricant to the bottom of the filler hole.
  26.  
  27. Install the brake drum and wheels and lower the car. Check for leaks and road test the car.
  28.  

DETERMINING GEAR RATIO



Determining the axle ratio of any given axle can be a very useful "tool" to the contemporary car owner. Axle ratios are a major factor in a vehicle's fuel mileage, so the car buyer of today should know both what he or she is looking for, and what the salesperson is talking about. Knowledge of axle ratios is also valuable to the owner/mechanic who is shopping through salvage yards for a used axle, who is repairing his or her own rear axle, or who is changing rear axle ratios by changing rear axles.

The rear axle ratio is said to have a certain ratio, say 4.11. It is called a "4.11 rear" although the 4.11 actually means 4.11 to 1 (4.11:1). This means that the driveshaft will turn 4.11 times for every turn of the rear wheels. The number 4.11 is determined by dividing the number of teeth on the pinion gear into the number of teeth on the ring gear. In the case of a 4.11 rear, there could be 9 teeth on the pinion and 37 teeth on the ring gear (37 ÷ 9 = 4.11). This provides a sure way, although troublesome, of determining your rear axle's ratio. The axle must be drained and the rear cover removed to do this, and then the teeth counted.

A much easier method is to jack up the car and safely support it with jackstands, so BOTH rear wheels are off the ground. Block the front wheels, set the parking brake and put the transmission in Neutral. Make a chalk mark on the rear wheel and the driveshaft. Turn the rear wheel one complete revolution and count the number of turns that the driveshaft makes (having an assistant here to count one or the other is helpful). The number of turns the driveshaft makes in one complete revolution of the rear wheel is an approximation of the rear axle ratio.

 
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