shazaam

Hi, folks. I'm new to the forums and hoping that someone here can enlighten me as to what might be going on with my 1998 Jeep Cherokee Classic (2WD Auto). I took it in to a local shop for some routine maintenance today (oil change, tire rotation, coolant flush), and, once the work was complete, the tech mentioned hearing a noise that suggested a problem with either the rear differential or transmission. They didn't have time to investigate, and, since I hadn't noticed any alarming noises previously, I decided to go ahead and drive it home and look into it later. So I went out, cranked it, put into gear, and headed for the parking lot exit. As soon as I began to move, I heard a god-awful grinding noise that seemed to be coming from the rear end -- I've never heard it before, and it certainly wasn't making that noise before they serviced it. So I parked it and went back in. The tech explained that this was the noise that he was referring to and repeated what he said earlier about it being either the rear differential or transmission. I had no alternative but to drive it home for today (luckily it was a short drive), and I had the pleasure of listening to that grinding noise all the way home. It's most apparent in low gear, and it drops off in intensity as soon the transmission shifts into third. It seems really suspicious that the noise began only after they'd had it up on the lift, but, at the same time, I don't want to jump to conclusions and blame them for something that's just a coincidence. Anyone have any thoughts as to what might be going on? Did they screw up and damage something? Would it even be possible for them to do that given the fact that they weren't even working on the transmission or rear differential?

DFlintstone

Just a thought...Take it somewhere for a free brake inspection. There might be an outside chance during the tire swap something in the rear got monkeyed up somehow.

If the grinding is that bad maybe the source of the noise could be found with the rear up on stands? I've seen shops do ridiculous stuff, but outright sabotage? Sheez, sure hope not! Check the fluid.

UnderPhoenix

Do you feel any resistance when the vehicle is in motion?

This sounds very peculiar to me but again I dont want to jump to conclusions and blame the mechanic. Take a look around and see if you can find signs of wear/rubbing or anything hung up.

shazaam

Thanks for the tips. Since my earlier post, I've come across an older thread where several people reported having very similar problems that might point to damaged planetary gears.

https://www.cherokeeforum.com/f2/gri...se-only-86237/

The suggestion to check the brakes is a good one, as well, but the fact that the grinding noise drops off substantially when the transmission shifts into third makes me wonder about the planetary gears explanation...

shazaam

No, I don't notice any resistance...nothing but the noise.

shazaam

I just talked to the owners of a couple of nearby transmission specialty shops. After describing the problem to them, they both concur that the planetary gear is the most likely culprit. Of course, they would evaluate it first since it might be something simpler and less costly, but, worst case scenario, they say that it will need a transmission rebuild. One shop quoted $1800 and the other quoted $2000 to $2500. How reasonable does this sound? It's interesting that they also said that these transmissions usually last 250K or more without a problem like this (mine has 135K, regular maintenance, and has never been used for towing).

Nate.S.

I had the same noise last weekend. Went to a fam get together and heard nothing, when we were leavin, I heard grinding. I just did a lift so I started checking bolts ect. Turns out my driver side lug nuts were loose.

shazaam

I'll check the lug nuts just in case -- thanks for mentioning it. I'm not encouraged by the fact that the noise I'm hearing changes as the gears shift, though. It's loudest in first and reverse, less audible in second, and I don't really hear it at all in third and fourth. Did you notice any change in the noise level or was it consistent at all speeds?

Nate.S.

At first I only heard it around 20-30mph. Then a few miles later it got louder and and was happening all the time. At first I thought it was just the tcase needing the drop after the lift.

I ARE EL1TE

It would be MUCH cheaper to swap a working one from the jy

shazaam

For future reference for anyone who might have similar symptoms, my transmission turned out to have broken teeth on two of the three planetary gear sets, as well as a pulverized bearing. It's not clear what happened first or why it happened at all, though. The shop owner who rebuilt my transmission said that, unless the vehicle is used for towing (which mine hasn't), the AW4 transmission is usually very reliable.