Rear Axle Seals
The rear axle seals are large rings that stop the oil inside the rear axle housing from leaking out. There is one seal for each rear wheel, located just in front of the axle bearing. The seals are long lasting but they can fail if worn bearings allow the shafts to deform them. Another cause of failure is a blocked breather port on the differential, which can allow enough pressure to build up inside the housing to rupture the seals. Signs that the seals has failed include the presence of oil around the rear wheels and reduced braking from oil falling on the brakes. Replacing the seals is not an easy task but it can be done without the service of a mechanic. The seals are cheap and can be purchases at most stores that sell automotive parts.
The rear differential is a set of gears inside a steel housing that is located between the rear wheels. It connects the engine drive shaft with both rear axle shafts. The role of a differential is to allows the wheels to turn at different speeds when the vehicle is turning. Like all moving metal parts, the gears and bearings need to be covered in oil to prevent abrasive wear. The rear axle housing is filled with oil, which the seals prevent from leaking out of the ends where the bearings support the axle shafts.
Rear axle seals can be bought separately or in packs that also contain wheel bearings. It's important to know the make and model of the vehicle before buying the seals because they can have slightly different sizes. Seals that are too small will leak oil, while seals that are too big will be damaged when inserted. Since it is very easy to damage the seals during installation, it is a good idea to buy several pairs. Extra gear oil may be needed to replace the oil which has leaked out. Brake cleaner may be needed to remove any oil that has dripped onto the brakes. The tools used to replace the seals include a jack, spanner set, screwdriver set, hammer and drip tray.
Replacing the rear axle seals takes considerable time and effort. The wheel, brake assembly and axle shaft need to be removed to gain access to each seal. Use a jack to raise the rear axle and remove the wheel and the brake assembly. Brake calipers can be left connected to the brake line but they should be supported by something other than the brake line. Place a drip tray under the differential and remove the cover to drain the oil from it. Remove the wheel axle and pull out the old seal. Before installing the new seal, clean the seat of any oil and debris.
Place a new seal into the seat and use a hammer to gently tap it into place. If the fit is too tight and more force is required, use the old seal to protect the new seal from the hammer. With the new seal in place, carefully insert the axle shaft, keeping it level to avoid warping the seal. Attach the backing plate to the axle housing, and then put the brake assembly and wheel back on. Once the differential cover has been put back on, put the old oil back in and bring it up to level with some new oil.
After all the excess oil has been cleaned up, the new rear axle seals should be tested with a short drive. During the drive, test the brakes to check that they are not slipping due to oil dripping on them. Afterwards, look for any new oil spots on the wheels, wheel wells and driveway. Also check that the oil level in the differential has not changed. Small oil leaks can take a while to become visible so check again after the vehicle has been left standing for several hours. Finally, this is only a general method for changing the rear axle seals. Always consult the service manual or a mechanic before attempting any major repair work.