I've noticed a humming noise from the rear driver side. I previously thought it was simply tire noise, but suspect that is not the case. I've paid attention to see if applying the brakes effects the noise and it doesn't. I will most likely need to take it to the shop, but was hoping for some feedback before doing so. Any suggestions will be appreciated.

I am experiencing the same exact situation with my 99 JGC. Took it to be looked at for possible brake hang up or bad bearing. Everything checked out ok, so now we are thinking that maybe the rear end is starting to self destruct starting at the drivers side carrier bearing. Anyone else have this problem?

best way to check it out if your concerned is to have the diff lube changed.

run a magnet thru the oil or let it sit in the oil for a while you clean up the inside of the housing.

gray filings are ok but shouldn't have any shiney ones.

I'd suggest synthetic diff oil for sure. It 'll run cooler and bearings and gears will last longer.

Tire noise can be mistaken for bearing noise at times so check that angle out too.

Jd

I will probably replace the fluids in both front and rear diffs over the weekend to see if it quiets the groaning/humming noise. I might even change out the transfer case fluid. I guess if the rear end does quiet down, I'll be looking at rebuilding the rear end soon. Any recommendations on fluids or additives?

Any recommendations on fluids or additives?

I used Mobil 1 in the front and rear with 4 oz of mopar limited slip additive in the rear.

for the transfer case I used amsoil ATF.

The synthetic will lower the gear box temp because the main source of heat is friction and synthetic is slipprier (sp) :)

JD

Maybe possibly perhaps a wheel bearing on its way out?

Could be a wheel bearing or maybe a dry ujoint too.

Mine has a bit of noise too, so I did the diff oil change thing front and rear. I pulled the rear axles, front hubs and both diff carriers while I had it apart. Not a thing to suggest a cause for noise - just normal bearing wear.

It was all good and no bad stuff in the oil so my mind is easy with the noise now.

We will see what change there is when I put on new tires next month.

JD