1990 Toyota 4Runner Replace the Rear Differential

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The early 90s Toyota 4 Runner was fitted with a single-wheel rear axle that was equipped with a drum-brake system. It featured a mechanical parking brake that was also attached to the rear drum-brake housing. From the factory, rear differential assemblies came with an "open" type of power delivery to the rear wheels. Service intervals are recommended at every 30,000 miles or 24 months, whichever comes first. The recommended lubrication oil is 2.5 quarts of 80w90 Hypoid gear oil.

Tools Used[edit]

Tools
10, 12, 14 and 24mm wrenches or sockets
Scraper or flat razor blade
Wheel star
Torque Wrench
Black RTV silicone gasket maker
Jack and jack stands
Wheel blocks or chocks
Hammer or mallet
Brake Fluid
2.5 qts. of 80w90 Hypoid gear lube
2 drain pans or oil safe containers

Replace the Rear Differential[edit]

Removal

  • Raise the rear of the vehicle off of the ground with a jack until you are clear to remove the rear tires.
  • Chock or block the front tires to prevent the vehicle from rolling in either direction.
  • Set jack stands beneath the rear axle housing tubes and lower the vehicle onto them.
  • Using an Allen wrench or socket, remove the rear-axle drain bolt from the housing and drain the gear oil into a safe and suitable container.
  • Using the appropriate tools, remove the rear wheels from the vehicle.
  • Using a hammer, knock the rear brake drum loose and remove it from the axle.
  • Place a suitable container under each drum-brake assembly.
  • Using a 10mm wrench, remove the brake lines from the drum assembly and leave in place.
  • Using a 14mm socket, unbolt the four nuts on the inside of the axle housing flange.
  • Remove the brake-drum assembly carefully, using your hands. The break drums are also attached to the rear axle shafts.
  • Using two 12mm wrenches, remove the four bolts from the rear drive shaft located at the rear differential drive flange. Using a 12mm socket, remove the surrounding nuts and cones holding the differential carrier assembly to the axle housing.

Installation

  • Using a scraper or flat razor blade, remove and clean both matting surfaces of the differential carrier assembly and axle housing.
  • Be sure to remove any visible metal shavings or debris that could have fallen into the rear axle housing.
  • Using black RTV silicone gasket maker, apply approximately a 1/8-inch bead to the matting surface on the axle housing.
  • Carefully reinstall the differential carrier assembly to the rear axle housing.
  • Secure it in place by reinstalling the nuts and cones hand tight.
  • Using a torque wrench, torque the nuts to 18 foot-pounds, working across from each other around the differential carrier.
  • Reinstall the rear drive line to the rear differential assembly and secure the nuts using the two 12 mm wrenches.
  • Carefully reinstall the rear axle shaft and brake-drum assemblies to the axle housing. Spinning the axle shaft drive flange may be necessary in order to align the splines.
  • Secure the drum-brake housing to the axle housing with the four nuts and the 14mm socket.
  • Reinstall the brake lines to the drum brake housings, using the 10mm wrench.
  • Top off brake fluid reservoir with the specified brake fluid.
  • Bleed the brakes, using a second person operating the brake pedal while you operate the bleeder screw located next to the rear brake lines at the rear brake-drum assembly.
  • Pump the brake pedal until the pedal feel is solid. With pressure on the pedal, loosen the bleeder screw until fluid emerges and then close it quickly. Repeat until all air is removed from both brake lines
  • Reinstall the drain plug, using the Allen wrench or socket.
  • Remove the oil-level check bolt with a 24mm socket located above the drain bolt on the back of the axle housing.
  • Fill the axle housing with approximately 2 qts. of recommended 80w90 gear lube.
  • Reinstall the wheels and torque to 85 foot-pounds.
  • Raise the vehicle with the jack and remove the jack stands to allow the vehicle to be lowered to the ground.