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Grinding noise/vibration from the rear when accelerating

C

Complex

NAXJA Forum User
Location
Nixa, MO
Need help figuring out what this is. I've got a 98 XJ Classic, stock axles front and rear, regeared to 4:56 with a Powertrax locker in the rear.

My problem is that when I accelerate or put on the gas a bit more, I can sort of feel and hear a grinding noise coming from the back end. It's not too loud, but it's noticeable, and only when you're on the gas. When you coast, it goes away.

Am I going to have to replace the whole rear end, or what? Could it just be the locker?

I'll answer any questions.. just need some help before I dish out the money for a replacement rear axle. This sucks, because I was getting ready to sell it too, but if there's something wrong with it I'll never get my asking price. :(
 
Mine is doing the same thing, I have a lock rite back there and it just started over the last month or so. But its definetly getting worse. Make sure its not something simple like ujoints or something before you spend on a new axle
 
97cntryxj said:
Is this right after you regeard the axle? after a lift was put on? How much lift do you have?
Click to expand...

No, all the work was done quite a while before I got it. It's an 8", probably settled at 6" though. Never had any problems before, but this noise started about a month and a half ago probably. I never thought anything of it until my dad drove in it with me and said it sounded pretty serious.
 
Mine had the exhaust pipe hitting the axle under acceleration. New springs solved a lot of problems for me. I had a shiney spot where the exhaust pipe hit the differential housing.
 
I'm hoping it's something as simple as u-joints. I can't afford to replace part or all of a rear end just to turn around and sell it. That's a huge hit in the money I'd be getting.
 
Check your tranny mount!!! It's easy to check, just lift tranny slightly with jack using block of wood to protect pan and observe the mount. If it appears to separate then replace. Not that expensive either, I had this problem and the mount was the source. If not that, then I wish you luck and better help to you from the rest of this forum!
 
It might have something to do with driveline angles. When you accelerate, it changes the pinion angle. That could be why it only shows then.

Which rear axle? I had a problem on my 8.25 when I got it regeared, and they didn't set the crush washer right. Drove fine for a while, then it failed and the rear diff went bye bye.

Have you checked the pattern (or had someone check it) to see if the gears are still lined up correctly?
 
I looked at it yesterday with my dad, and he noticed something almost instantly. Around the ends of the u-joints towards the rear, they are shiney. Well there is a small tab that comes out over the edge that is exactly the same distance out as the width of the shiney part. So we're thinking they are loose (there are also some hairline cracks in the metal where it is shiney), and are moving around slowly. The little tab is what is causing the shiney ring around the edge, because it's scraping the metal so much.
 
Hey man, check your tranny mount, mine was destroyed, and it was hard to tell. I had to pull the t-case cross member to tell. Mine vibrated really bad from start to the shift into 2nd gear. When I pulled the mount it came out in 3 pieces. Start there before you go buy a rear end. In fact I have a mount that was only used for 3 months I could sell you cheap! Let me know.
 
I thought I might have broken part of the t-case chain and was getting horrible grinding noises and vibes. The u-bolt/pinion strap bolts came loose on my 8.25. Just one more thing to check, I guess.
 
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