After buying ZJ 4.0 selectrack last year, we rebuilt rear diff. It was quiter before, but now i can hear roaring sound. it is faint but it is there. how can i understand if it is due to bad bearings at rear wheels? how to diagnose?

 

take cover back off and take a peak

 

Jack up the rear of the vehicle & support it with stands. Then remove the wheel and the brake drum. See if the is any play by attempting to move the axle flange up, down, fore, aft. Also when you turn the axle shaft you may feel it binding.

 

A leaking axle seal is also a good warning of the bearing being bad. You should look carefully at the shaft to make sure the bearing did not wear a groove into it, you MUST replace the axle shaft if there is a groove worn into it.

 

understood. thank you for info. how about the bearing sound characteristics? is there a way of telling diff is still ok without removing the cover?

 

So I did this today (jacked up removed hub) and it looks clean and no leaks, but I get a little movement back and forth. Also, I have a little bit of noise coming out of the rear driver side at low speeds. Think mine sound shot?

 

C-clip axles will have a bit of in and out play. your looking for side to side or up and down

 

Thanks for the reply. Not any of that I noticed.

 

This sounds like a good start but the real test is the axle flange run out?
This can be checked with a Dial Indicator gauge just turning the axle 360.
Does any one know how much run out ok?

I just tested both of my rear axles drivers side .015 and passenger .010.

What is too much axle flange run out is the best question?

 

Those answers are all respected but leave out the bearing noise under load and while you are driving. Not to change the subject but I had bearing noise in my acura. I did all the shaking up and down left and right to every wheel and I everything was just fine with not enough movement to conclude that the bearings were bad. I listened too much to mechanics and changed all of my 4 tires with new ones and nothing happened. One mechanic was telling me my transmission is grinding and it is going bad. One day I dedided that enough is enough and I am going to use some common sense approach. The car has 225,000 miles on it and I am going to put new hubs/bearings on it becuase it could use them. I did just that and all of my road noise problem went away. At first the car drove like it was glude to the road. After changing the bearings it drives easier and I feel like it is giving better gas millage. My point here is that don't leave out the fact that those tests leave out the load while you are driving. now back to cherokee and the reason I am on this site. I am the new owner of a 1992 cherokee that seems to have the same problem. At 55-60 miles the road noise is realy load. It has 171,000 miles on it. Instead of going around and paying for the wrong appoinions, I may want to change some parts starting with putting new bearings on it all around. Thank you for hearing me my friends.

 

Sorry for bringing this back from the dead, but my curiosity is piqued. Why does the seal leak when the bearing goes bad?

Mine had this exact thing happen. The bearing was bad, and the seal was leaking. I thought it was just that the seal let fluid out of the diff and ran the bearing dry.

 

The bearing wears a groove into the axle shaft, that allows the shaft to move up in the axle housing and the bottom of the seal loses contact with the shaft letting the oil to escape.

 

Hmm... So it's not play in the bearing, it is wear in the shaft? Does that mean I will have the same issue with the new stock bearing and seal I just installed this morning?

The shaft looked fine and didn't appear to feel grooved?

 

You might be ok, just keep an eye on it.

 

Gonna have to bring this thread back once again. any help would be appreciated..
Im also getting a weird noise coming from the rear diff on my 95 cherokee chry..8.25
underload while driving getting a strange clicking noise ( like baseball card in bike spoke )
throw it in neutral while truck is rolling -- no noise--
jacked up the rear axle on jack stands put the jeep in drive, heard no noise but only one wheel spins..
possible bad axle? wheel bearings? or etc?
already checked pinion gear and internal's inside diff, and nothing seems broken, cracked or loose. rear Drive shaft had also be re checked and serviced.

thnx for any words from the axle gods..