Peter Boyer
While not an overly difficult DIY project, replacing the rear axle seal does require some planning and specialty tools.
Words by Peter Boyer
Rear axle seal failures are not uncommon on Jeep Wranglers. But, with the severe use that the seal encounters in a 4X4 rig, and its minimal design, it’s surprising that it doesn’t fail more often. This repair is fairly straightforward, as we shall see, except for the requirement to use some specialty tools that may be out of the comfort zone of some DIY mechanics.
However, don’t be intimidated. Like all mechanical repairs, a careful step-based approach, an understanding of the functions of each component involved and having the right tools for the job makes these repairs much easier with efficient results. If you decide to have your local shop do it for you, you’ll get a clear understanding of why it costs what it does for the parts and labour!
One telltale sign that the axle seal has failed is the noticeable oil at the bottom of the backing plate of one of your rear wheels or an oil-spray mark on the inside of the rear tire. This seal is designed to contain the gear oil in the differential and axle tube, while allowing it to lubricate the rear wheel bearing located at the far end of the axle, where the rear brakes and wheel bolt on at the axle hub.
What Causes a Rear Axle Seal to Fail?
Longevity
Some seals seem to last forever, but many don’t. Friction from the axle shaft spinning on the tight, thin lip of the seal simply wears and in the case of my 2011 JK with low mileage, I suspect that age is a factor as the flexible compound the seal is made of lost resilience and was no longer able to hug the axle shaft tightly enough to retain the gear oil.
Normal deterioration happens slowly, which is why it’s important to inspect your vehicle regularly, particularly once it exceeds 100,000 km (62,000 mi). If a small oil leak goes unnoticed, it will only increase, and accumulate to contaminate the nearby brake components, increasing the cost of the repair.
Premature Failure
Premature failure may include a defective seal, improper installation, or inadequate maintenance related to exposure to dirt and contaminants. A defective seal is the least likely of these possibilities given today’s quality manufacturing capabilities (but it could occur, nonetheless). A more likely cause of premature failure is a recurring repair from improper installation the first time, such as improper alignment during installation, or a scored axle shaft during bearing removal.
My speculation is that most premature rear axle seal failures on Jeeps are caused by dirt, water, and rust compromising the external surfaces of the axle. Going off-road exposes chassis components to mud, sand, gravel and water. It’s extremely difficult to clean a chassis after total immersion in muddy water even with a pressure washer. This is where regular brake service is important as components are disassembled, checked and cleaned thoroughly with brake cleaner and compressed air. Even though the seal is somewhat protected inside the hat of the rear rotor, it’s amazing how much debris can accumulate in the area.
Replacing the seal:
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Secure a jack stand under the side of rear axle that needs to be repaired. This will raise the wheel slightly and prevent gear oil from running out of the axle tube once the axle is pulled. Cleanliness is next to godliness when doing mechanical repairs – not only for convenience, but it keeps the surfaces of moving parts as clean as possible during reassembly.
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Remove the 18mm bolts holding the brake caliper and gently remove the caliper, securing it on the suspension so it doesn’t hang on the brake line. Remove the four 18mm nuts from the axle retainer and the 8mm small bolt that holds the ABS sensor in place. It’s not necessary to remove the ABS sensor completely, pulling it through the backing plate as far as it goes should be sufficient. If you own an older Jeep like mine, these bolts and nuts will be rusty and definitely need some penetrating oil and a careful application of heat to remove so that they can be reused.
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Everything is now ready for removal. Use a slide hammer to coax the axle retainer, seal, wheel bearing and collar retainer out of the axle tube. This shouldn’t be difficult, but may require two or three firm taps. Have a rag ready to wipe up any oil that might be released when the axle is removed and slide the axle assembly out of the axle tube. I borrowed a slide hammer from my local CTC store, through their loan-a-tool program, at no cost.
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Stuff a clean rag in the axle tube to prevent any debris from entering, and clean the backing plate with brake cleaner. Closely inspect the wheel hub for any damage. If the oil leak is significant and the brake shoes are saturated with oil, they’ll need to be replaced. In my case, I discovered the leak early while servicing the brakes and the brake shoes were fine so I simply cleaned them up with brake cleaner.
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Sometimes the outer race of the tapered bearing comes out of the tube at the same time, but more than likely it will still be in the axle tube if you can see the exposed tapered bearings. You can remove the race by hand, grabbing the edge with a pair of pliers if it protrudes slightly, or by attaching a washer smaller than the diameter of the axle tube to your slide hammer and positioning the washer on the back edge of the race and tapping it out. Sometimes slide hammer kits come with puller attachments. Mine didn’t so I improvised with a thick washer of suitable diameter.
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Always be sure to take a photo of the order and placement of the components before disassembly to use as a reference during reassembly.
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Use a grinder with a cutting wheel to remove the collar retainer and wheel bearing, making sure not to cut completely through to prevent scoring the axle shaft in the process. This is the trickiest part of the job. Just take your time, allowing your cut as close to almost through as possible. Then use a cold chisel to tap off the collar retainer and the inner bearing race. When the cage holding the individual tapered bearings is cut, remove it with a pair of pliers so the cut on the inner race can be accomplished carefully. Note: Once the cuts have been made nearly through, the strength of the parts is compromised, and they can be removed using a hammer and a cold chisel.
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Remove the seal and the axle retainer by sliding it off the axle. I like to check the seal once it’s removed. In my case, the seal had just started to leak and looked alright to the naked eye. But it was extremely crusty and dirty and it was also 10 years old – time for a new one!
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On the work bench, reassemble the new components in the proper order and facing the correct way starting with the axle retainer, seal, bearing and collar retainer. Refer to the photo and make sure that everything is in the proper order and facing correctly on the shaft so it will reseat into the axle tube.
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With some clean machine oil on the axle, use a hydraulic press to gently press the bearing and the collar retainer into place. If you don’t own a press, take the axle to a machine shop or your local mechanic and ask them if they could perform this step for you. It will only take a few minutes and should be an inexpensive service. I just reached out to Jamie at H&R Machine Shop in Fergus, ON, who did the honours.
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Next, slide the axle into the axle tube, taking care to line up the splines on its end within the differential, and gently press it into place by hand. Make sure the notched side of the axle retainer corresponds with the ABS sensor location. The axle should slide easily into position. Once the axle is in place, slide the ABS sensor back in position on the backing plate and install the 8mm bolt.
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Bolt everything back up. I didn’t find a torque setting for the axle retainer nuts, so I used ‘G&T’ (good and tight), and 77ft/lbs for the caliper bolts. All is now good to go for another 100,000 km (62,000 mi). However, keep a close eye on it for the next 50 km, while everything reseats into place.