GM Cadillac 1967-1989 Repair Guide

Final Drive Unit (FWD Only)

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The final drive unit is secured to the transmission by six screws. It is held at the front by a support bracket which is attached to the engine block.

The 8 in. ring and pinion gear set is the hypoid type, having the pinion above the ring gear center. A splined transmission output shaft fits into and rotates the drive pinion gear. Two preloaded tapered roller bearings are used to support the drive pinion in the housing.

When the pinion nut is tightened, a spacer is compressed between the outer bearing and a shoulder on the pinion stem. This spacer allows bearing preload adjustment. The fore and aft position of the drive pinion is adjusted by the use of a measured shim placed between the drive pinion head and the inner bearing.

Torque from the drive pinion is transferred to the ring gear attached to the differential case. The case is held in the final drive housing by two tapered roller side bearings. Shims are used to adjust and maintain preload on the side bearings. Proper ring gear to pinion backlash is obtained by varying the shim thickness from side to side. Two side gears, inside the case, have splined bores for driving the output shafts. They are positioned to rotate in counterbored cavities in the case. Two pinion gears, also inside the case, have smooth bores and turn freely on the pinion cross shaft. The pinion gears are in constant mesh with the side gears and act as idler gears when wheels turn at different speeds. These gears are backed by steel thrust washers and the cross shaft is retained by a roll pin.

REMOVAL & INSTALLATION



See Figure 1

1967-78 Eldorado
  1. Disconnect the negative battery cable.
  2.  
  3. Unbolt the transmission filler tube bracket and remove the filler tube.
  4.  
  5. Remove screws A, B and the nut H.
  6.  
  7. Disconnect the transmission cooler lines from the final drive support bracket and slide the clip out of the way.
  8.  
  9. Remove the locknut, washer and long through-bolt holding the final drive support brace to the engine mount bracket.
  10.  
  11. Remove the right hand output shaft.
  12.  


CAUTION
The shock absorbers act as rebound stops. Before performing the following Step, be sure that the right hand shock absorber lower sleeve cannot be dislodged from the stud.

  1. Place jackstands under the front frame side rails and lower the hoist that was used when removing the right hand output shaft.
  2.  
  3. Remove the final drive cover and allow the lubricant to drain into a drain pan.
  4.  
  5. Remove the 6 screws holding the left hand drive axle to the output shaft. Compress the drive axle inner C.V. joint and hold it in this position to remove the final drive unit with the left hand output shaft installed.
  6.  
  7. Remove the bolt, washer, and nut holding the left tie strut to the frame crossmember. Loosen the bolt holding the strut to the side rail and rotate the strut outboard until the strut is clear of the final drive area.
  8.  
  9. Remove the large through-bolt nut and washers, securing the final drive support bracket to the final drive.
  10.  
  11. Remove the final drive support bracket.
  12.  
  13. Remove the final drive cover and gasket(s).
  14.  
  15. Remove the final drive with a transmission lift and adapter. The adapter should have a rotating feature to ease removal and installation.
  16.  
  17. Place a drain pan under the transmission and remove screws C, D, E, F and nut G.
  18.  
  19. Disengage the final drive splines from the transmission and let the unit drain.
  20.  
  21. Remove the final drive unit from under the car by sliding the unit toward the front of the car and permitting the ring gear to rotate over the steering linkage. Lower the housing from the car.
  22.  
  23. Remove and discard the final drive-to-transmission gasket.
  24.  

To install:
  1. Positioning new gasket on transmission, install final drive unit, permitting ring gear to rotate up over steering linkage.
  2.  
  3. Align final drive splines with splines in transmission.
  4.  
  5. Align bolt studs G and H on transmission with holes in final drive.
  6.  
  7. Install bolts C, D, E and F and nut G finger-tight.
  8.  
  9. Install support bracket on final drive unit.
  10.  
  11. Install other support brackets.
  12.  
  13. Install bolt in fluid cooler lines, clamp and tighten to 8 ft. lbs. (11 Nm).
  14.  
  15. Tighten bolts C, D, E and F and nut G to 25 ft. lbs. (34 Nm).
  16.  
  17. Reposition left drive axle and install screws to 65 ft. lbs. (88 Nm).
  18.  
  19. Install right output shaft and axle.
  20.  
  21. Position final drive cover to final drive and install screws to 30 ft. lbs. (41 Nm), through 1973; 13 ft. lbs. (10 Nm) for 1974-78.
  22.  
  23. Fill final drive unit. Tighten lower shock.
  24.  
  25. Install wheels and tires, tightening nuts finger-tight.
  26.  
  27. Lower car and tighten wheel nuts to 105 ft. lbs. (142 Nm) through 1972; 130 ft. lbs. (176 Nm) for 1973-78.
  28.  
  29. Install bolts A and B and nut H, tightening to 25 ft. lbs. (34 Nm).
  30.  
  31. Install new O-ring on transmission filler tube, remove plug in filler tube hole and install filler tube.
  32.  
  33. Position the transmission cooler line clips and secure the support bracket with the screw.
  34.  
  35. Connect battery.
  36.  
  37. Check/add engine oil and transmission fluid. Start engine and add fluid as needed.
  38.  
  39. After running check the seals for leaks.
  40.  



Click image to see an enlarged view

Fig. Fig. 1: Final drive-to-transmission assembly - 1967-78 models

1979-85 Eldorado and 1980-85 Seville

See Figure 2

  1. Disconnect the negative battery cable and raise the car. Place jackstands underneath the front frame horns and the lower front post.
  2.  
  3. Remove the frame brace attaching bolts and pivot the braces outward in order to gain access.
  4.  
  5. With a drain pan under the final drive cover, loosen the final drive cover screws and allow the fluid to drain. Remove the cover and gasket material.
  6.  
  7. Remove the screws on both sides attaching the output shaft to the drive axle. Separate the flanges of the shaft and axle to obtain clearance. The final drive assembly will be removed with the output shafts installed.
  8.  
  9. Remove the battery cable retaining screws from the right output shaft and the screws securing the support to the engine block. Rotate the support downward for clearance.
  10.  
  11. Remove the screws which attach the final drive shield to the transmission and the support bracket. Remove the shield.
  12.  
  13. Remove the remaining final drive screws.
  14.  
  15. Remove the final drive support-to-engine block attaching screws.
  16.  
  17. Using a puller, separate the steering linkage from the pitman arm. Push the linkage toward the front of the car.
  18.  
  19. Slide the final drive assembly forward, off the transmission shaft and remove the unit. Do not hold the unit by the output shafts as the seals or splines could easily be damaged.
  20.  

To install:
  1. Thoroughly clean all the gasket surfaces and position a new gasket on the final drive. Do not use a sealer on the gasket.
  2.  
  3. Align the final drive assembly, with the output shafts attached, to the transmission and install all the attaching screws except the one used to hold the shield. Torque in rotation to 30 ft. lbs. (41 Nm) in two steps.
  4.  
  5. Loosen the front support bracket screws and install the bracket to the engine block while holding the bracket flush on the housing pad. Torque to 50 ft. lbs. (68 Nm).
  6.  
  7. Install the final drive shield. Torque the drive-to-transmission screw to 30 ft. lbs. (41 Nm) and the bracket-to-housing screws to 34 ft. lbs. (46 Nm).
  8.  
  9. Align the right output shaft support with the attaching holes in the engine block. Do not allow the shaft and support assemblies to hang from the drive unit. By moving the flange end of the shaft up and down and installing the screws and washers loosely, locate the centered position. Torque the screws to 50 ft. lbs. (68 Nm).
  10.  
  11. Install the battery cable retainer.
  12.  
  13. Align the right drive axle to the output shaft and install the attaching screws. Torque the screws to 60 ft. lbs. (81 Nm). Repeat for the left side.
  14.  
  15. Position a new cover gasket or apply silicone sealer on the final drive cover. Install the cover and torque the screws to 7 ft. lbs. (9 Nm). Refill the unit. Torque the filler plug to 30 ft. lbs. (41 Nm)
  16.  
  17. Install the steering linkage to the pitman arm and torque to 60 ft. lbs. (81 Nm). If the cotter pin hole does not align properly, tighten the nut slightly. Do not loosen to align. Install a new cotter pin.
  18.  
  19. Install the frame braces and torque the nuts to 50 ft. lbs. (68 Nm).
  20.  
  21. Lower the car, connect the battery cable, start the car and check the transmission fluid. When the final drive has reached operating temperature, check it for leaks.
  22.  



Click image to see an enlarged view

Fig. Fig. 2: Front wheel drive components - 1979-85 models

 
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