REMOVAL & INSTALLATION 1979-90 Models
See Figures 1 through 9
- Raise the vehicle and support it safely on stands.
- Remove the rear wheel.
- Remove the rear brake drum.
- Disconnect and plug the brake line(s) at the wheel cylinder. A small container will be needed to catch the leaking brake fluid before the line is plugged. If a plug for the line is not available, drain the brake fluid into a container.
- Disconnect the parking brake cable from the shoes and remove the cable from the backing plate.
- Remove the 4 nuts behind the brake backing plate holding the bearing case to the axle housing assembly.
- Remove the backing plate, bearing case and the axle shaft as an assembly. If this is not possible by hand, use a slide hammer to remove the assembly.
- Remove the O-ring and the bearing preload shims. Save the preload shims for reassembly.
- Remove the oil seal from the axle tube with a hooked slide hammer.
- To remove the axle shaft bearing, remove the notched locknut with tool MB990785-01 or a brass drift.
- Remove the lockwasher and flat washer.
- Screw the locknut back on to the axle shaft about 3 turns.
- If tool MB990787-01 is not available, it will be necessary to fabricate a metal plate that fits over the axle shaft and abuts the locknut. Drill 4 holes in the plate that align with the 4 bearing case studs and fit the plate onto them. Refit 2 nuts and washers to the bearing case studs diagonally across from each other and tighten them evenly to free the bearing case and the bearing.
- Use a hammer and drift to remove the bearing outer race from the bearing case.
- Remove the outer oil seal from the bearing case.
- Apply grease to the outer surface on the bearing outer race and to the lip of the outer oil seal. Drive them into the bearing case from each side.
- Slide the bearing case and bearing over the rear axle shaft. Apply grease on the bearing rollers and fit the inner race by pressing it into place. Be careful not to damage or deform the dust cover.
- Pack the bearing with grease.
- Install the washer, crowned lockwasher and the locknut in that order, then tighten the locknut to 130-159 ft. lbs (176-215 Nm).
- Bend the tab on the lockwasher into the groove on the locknut. If the tab and the groove do not line up, slightly tighten the locknut until they do.
- Drive the new inner oil seal into place after greasing it and refit the assembly.
- Install a new O-ring, install the shims and apply silicone rubber sealant to the face of the bearing case.
- Install the entire assembly to the axle housing. Tighten the retaining nuts to 36-43 ft. lbs. (48-58 Nm).
- Check the axle shaft end-play. If it is not between 0.0020-0.0079 in. (0.05-0.20mm), proceed with the axle shaft end-play adjustment procedure.
- If the end-play is within specifications, install all removed brake parts and bleed the system.
- Install the wheel and lower the vehicle.
- Road test the vehicle. Check for leaks.
1991-93 Models See Figures 10 through 18
- Loosen the wheel lug nuts only 1 / 2 a turn.
- Raise and support the vehicle on jackstands.
- Remove the wheel(s) from the vehicle.
- Remove the parking cable attaching bolt and disconnect the parking brake cable end from the brake assembly. Remove the parking brake assembly from the end of the axle-refer to Brake Operating System for this procedure.
- On vehicles with the ABS system, remove the speed sensor.
- Remove the brake tube. Before disconnecting the brake tube, drain the brake fluid from the bleeder screw at the left side of the rear brake.
- Pull the rear axle shaft out of the axle housing. If the rear axle shaft is difficult to remove, use a slide hammer (impact puller) to remove it. Remove the shoe from the brake assembly.
- Remove the shim, O-ring and snapring from the inside end of the axle shaft. Remove one retainer bolt from the backing plate with a plastic mallet. Apply gummed cloth tape around the edge of the bearing case for protection. Fix the axle shaft in a vise or with a similar method. Using a grinder, grind down the retainer flat, on one side, until the thickness of the retainer is only 0.04-0.08 in. (1-2mm). That is that the retainer is ground down toward the axle shaft, not toward the flange. Cut, with a chisel, the place where the retainer ring has been shaven down and remove the retainer.
Only the retainer ring is to be ground down-NOT the axle shaft, the axle flange, the bearing or any other component.
- To remove the rear axle shaft, reinsert the lock nut on the shaft approximately 3 turns. Install the special tool MB 990787-A to remove the bearing case from the axle shaft. Be sure to install the nuts and washers diagonally.
- Turn the nuts with equal; pressure to ensure smooth removal of the wheel bearing.
- When removing the bearing outer race, use a hammer and drift to separate the outer race from the bearing case.
- Remove the oil seal from the end of the rear axle housing using the tool MB990211-01 (slide hammer with a hooked end), if necessary.
- Check the dust cover for deformation or damage. Check the oil seal for damage. Check the inner and outer bearings for seizure, discoloration and rough raceway surface. Check the axle shaft for cracks, wear and damage. For there are any of these indications, replace the part with a new one. The retainer, the bearing inner (inner and outer) and outer races and the oil seal need to be replaced with new components upon reassembly. After all of this work, it is probably a good idea to replace the bearings and the axle housing tube oil seals.
- Apply multipurpose grease to the oil seal fitting area of the axle housing.
- Drive the seal into the housing end using a seal driver. Apply multipurpose grease to the oil seal lip. Apply the great to the external surface of the new oil seal. Press fit the new seal into the bearing case until it is flush with the face of the bearing case.
- To install the outer bearing case, apply multi purpose grease to the external surface of the bearing outer race, then press fit the bearing outer race into the bearing case.
- Apply the same grease into the roller surfaces of the bearing inner race. Install the rear brake assembly attached with the bearing case and the bearing inner race in that order to the axle shaft. Press fit the bearing inner race into the axle shaft. Pack the bearing case with multipurpose grease.
- When pressfitting the retainer ring, use tool, MB990799, and press in the retainer to the axle shaft, confirm whether or not the pressure input is in the standard value or not. In case the initial pressure input is less than the standard value, replace the axle shaft.
- After snapring installation, measure with a feeler gauge the clearance between (A) snap ring and the retainer ring to see if it is in the standard value. Standard value is less than 0.0065 in. (0.166mm).
In case the standard value exceeds 0.0065 in. (0.166mm), select and install a snap ring by referring to the list so to make it in the standard value. Use the following adjusting snaprings:
Thickness of snapring-identification color.
- Install the whole axle assembly into the axle housing. Make sure that the grooves on the end of the axle shaft line up in the differential. Use a plastic or rubber mallet to help "persuade" the axle shaft into the differential unit. Tighten the four retaining bolts for the axle shafts to 36-43 ft. lbs. (50-60 Nm).
- Attach the parking brake cable.
- Place the brake drum onto the axle shaft.
- Tighten the brake hose to the frame brake line. Tighten the flare nut to 11 ft. lbs. (15 Nm).
- Install the wheels and tighten the lug nuts as tight as possible with the vehicle not on the ground.
- Bleed the brake system-refer to Brake Operating System for this procedure.
- Lower the vehicle until the wheels are touching the ground, then finish tightening the lug nuts. Lower the vehicle the rest of the way to the ground.
- Road test the vehicle and check for leaks.
See Figure 19
- Begin with the left side rear axle assembly and insert a 0.039 in. (1mm) shim between the bearing case and the axle shaft housing. Tighten the nuts to specification.
- Install the right side axle assembly into the right side housing without its shim and O-ring. Tighten the 4 nuts to about 4 ft. lbs. (6 Nm).
- Using a feeler gauge, measure the gap between the bearing case and the axle housing face.
- Remove the axle shaft and select a shim or shims that is the equal to the sum of the clearance measured in Step 3 plus 0.002-0.008 in. (0.05-0.20mm) and install them on the housing. Install the O-ring and apply sealant.
- Install the axle assembly and tighten the nuts to 36-43 ft. lbs. (49-59 Nm).
- Measure the end-play and complete the installation procedure.