Your unit bearings are the main bearing that keeps your wheels turning on the outer part of your axle. They will need to be replaced once in a while. The time frame for this will depend on how often you wheel, the mileage on your Jeep TJ, and many other factors like how often you see mud, etc. when it comes to replacing them you will need a little grunt work, but it’s generally a job anyone with basic tools can do. You will save yourself some time (likely, depending on your time to get to/from the mechanic), and some money. Ok, enough babbling, on to the install!
- 13mm 12 point socket
- 13mm wrench
- 3/4″ deep socket
- Breaker bar
- 36mm 6 point socket
- 1/4″ 12 point wrench
- Pliers or Needle nose pliers
- BFH (big f’in hammer)
- Metal chisel
- Floor jack or bottle jack
- Jack stands (at least one, two is better)
- Unit bearing(s)
- Bearing grease
- 1-1.5 hours
1: Park your Jeep TJ, leave it in gear and put on the e-brake. Chock your rear tires. Crack the lug nuts on the side you intend to work on first. Jack the tire up off the ground by your axle and place a jack stand under it. Remove the tire and place it underneath the axle.
2: Remove the two caliper bolts from the back of the caliper with a 13mm wrench. Once you crack them they should turn out by hand as they are greased (or should be). Keep them clean and set them aside. You can then grab the top of the caliper and pivot it outwards to remove it from the rotor. Try not to leave it hang by the brake line.. you can set it on the tire, grab a wood block to set it on, tie it up with zip ties to something.. whatever you can find.
3: Remove the rotor. Check the wheel studs for retaining clips. If there are still some on there you can remove them with some pliers or side cutters. The rotor should just pull off by hand, but it might not. If you are having troubles getting it off by hand, some taps on the face of it (in between the studs not where the brake pads touch) with a hammer should do the trick to break loose the rust holding it on.
4: Remove the cotter pin that holds in the slotted retainer. Careful not to lose the spring behind the retainer when you remove it. You can now remove the axle nut. These are torqued down to 175ft lbs, so you will need that 36mm 6 point socket and a breaker bar. You also might need a little more leverage on the breaker bar.. a piece of tubing of a hi-lift handle works well. If you need a way to keep the axle shaft from spinning while you break it, I’ve got two simple methods for you. If you have a front locker, put it in 4wd and lock the front. That will allow the traction of the rear tires touching the ground to keep the front from spinning. The second method is to place a pry bar through your u-joint yoke so it will hit on the axle knucle stopping it from spinning. Once it’s cracked remove it and the washer behind it.
5: Turn your attention to the back of the steering knuckle. There are three 12pt 13mm bolts that hold the unit bearing on. Remove these… they are usually very tight from the factory. It says 75 ft lbs in the service manual, but I don’t believe it. I used a 12 point wrench and another larger wrench (box end) on the end of that one as leverage. Probably not something that’s *good* for the wrenches.. but it works good!
6: You can then remove the unit bearing. It might come off by hand depending on the age of your Jeep TJ and the type of wheeling you do. If not, I’ve got three methods that will hopefully help you out.
method 1: Put the tire back one and use a large breaker bar to pry the tire off. You can pry from anything you need, like a lower control arm, etc. Be careful and make sure you are prying on something strong!
method 2: Use a hammer and a steel chisel to tap around the edge of the unit bearing. It does take some effort, and it will likely scar up your dust plate a little bit.. but it works great.
method 3: I cannot take credit for this one. I found this method over on Stu Olsen’s site, and he gives credit to his friend Blaine (mrblaine on jeepforum). So, thanks to both of you! Find an appropriate size nut and bolt (grade 8 is better). Place one side of the bolt on the inside of the steering knuckle right beside where the axle shaft disappears into the axle tube. The other side should be resting on the outer axle shaft yoke that holds the u-joint. You can adjust the bolt length with the nut to get it to rest in there. You can then turn the steering wheel to force outwards pressure on the yoke, which will unseat the unit bearing. If you are having troubles visualizing what I mean, click the fullsize version of the image above.
7: You can then pull the unit bearing out. This will require holding the axle shaft in while you pull it out to separate it from the shaft. You can just leave the shaft and dust sheild hanging for now. Grab your new unit bearing and grease the contact point a little bit so it won’t sieze up with rust for next time! Grease up your axle shaft splines as well, and put the new one on. Line up the splines, and the dust plate and put the three bolts back in that hold it to the knuckle and tighten them to 75 ft lbs.
8: I’m not going to write too much about putting it all back together because you’ve just learned how all this stuff works! Put your large washer, and axle nut (175 ft lbs) back on. Next is the spring washer and slotted retainer with cotter pin. Then you can put your rotor and brake caliper back on. The brake caliper should be placed on the downside first, then swung upwards.. the exact opposite of taking it off. You then put the two 13mm bolts back in and torque them to only 11 ft lbs. Reinstall your tire and tighten up the lug nuts a bit (criss-cross pattern) just so the rim is seated properly. Put your jeep back on all fours, and tighten the lug nuts to 95 ft lbs using a criss cross pattern as well.
Congratulations, you’re a pro; you’re ready to do the other side now! Aside from a couple hitches (like getting the damned unit bearing off) this was a pretty straight forward and easy install. Unit bearings can be had brand new for about $80-$100, and I would hazard a guess that the labour alone to take a job like this to a shop would be more than that.. so pat yourself on the back and have a beer! Hopefully your jeep’s nasty noise has gone away.