The Mustang II came equipped with two different rear axles. The 6 3/4-inch rear axle was used in four- and six-cylinder cars and the 8-inch rear axle was used in some six cylinder and V-8 equipped cars. Both axles used a pressed on axle bearing with a bearing retainer that secures the bearing and axle inside the axle housing. Replacement of the axle bearings in these axles requires the use of a hydraulic bearing press and a bearing separator to slide the axle bearing off the axle.
Place the wheel chocks against the Mustang's front tires and kick with your heal to secure the vehicle. This will prevent the vehicle from rolling during the repair. Loosen, but do not remove, the lug nuts on the rear wheels using the lug wrench. Position the floor jack under the center of the rear differential (also called the rear end) and raise the Mustang until the rear wheels are off the ground. Slide jack stands under the differentials rear axle tubes between the differential and the wheel. Lower the car onto the stands and roll the jack from under the car.
Remove the lug nuts and roll the wheels out of the work area. Slide the brake drum off of the rear brakes. If it doesn't slide off easily by hand a few sharp blows with a hammer will loosen it from the axle so it will slide off. Lay the drums aside.
Unscrew the four 1/2-inch nuts that attach the axle bearing retaining plate to the axle tube. The retaining plate also locates and secures the brake backing plate to the axle tube. Hold the brake backing plate in position and slide the axle from the axle tube. If the axle is stuck in the tube a slide hammer can be used to pull it out of the axle tube.
Bolt the bearing separator securely around the axle between the bearing and axle flange. Lower the work surface of the press and place the bearing separator on the work surface so that the axle flange is between the two steel beams of the work surface and the hydraulic piston of the press.
Tighten the release knob on the press' hydraulic bottle jack. Insert the pump handle into the bottle jack's lever. Pump the handle until the press pushes the axle through the old bearing and bearing retainer. Loosen the release knob and remove the axle from the press.
Unbolt the bearing separator from the axle. Slide the new bearing and the new bearing retainer ring down over the axle. Move the work surface up towards the hydraulic piston.Slip the axle between the steel beams on the work surface and lay two 1/2-inch thick steel supports across the beams to support the bearing and retainer. Push the axle into the bearing and retainer, using the press in the same manner it was used to remove the bearing, until the bearing is seated completely flush on the axle.
Reinstall the axle through the brake backing plate and into the axle tube. Use the axle flange for leverage and push the axle into the splines inside the differential. It may take several tries to locate the splines with the end of the axle.
Reinstall the brake drum and wheel. Raise the car off the stands and remove the jack stands before lowering the jack until the wheels are on the ground. Tighten the lug nuts securely. Add gear oil, as needed, to the differential and test drive the Mustang.
