Rear End Thumping Sound

**bigmac776** · 11-19-2006, 12:08 PM

All right guys, I need some help. I have a thumping sound coming from my rear end. It occurs when I'm driving straight and when I turn left but goes away when I turn right. It also does it when I let off the gas. I went through the rear end and replaced all of the bearings in the differential, put new Mosier axles and wheel bearings. Set up on the pinion depth and backlash looks good and preload is set up correctly. After all of that work, the noise is still there. Has anyone had a similar noise? Could my limited slip unit make a clunking noise? It sounds similar to a tire that has a flat spot but it's definitly in the rear end. Oh yeah I replaced the U-Joints as well. I am suspect of the limited slip unit. It's about the only thing I haven't messed with.

**dafaic** · 11-23-2006, 09:16 PM

I have a similar issue that started tonight after some spirited driving. If i let off the gas a loud thumping sound come from the back driver side. I thought i had a flat tire or something at first. I kinda been leading to a wheel bearing but not sure? Specially after all the reading I have been doing and stories like your's bigmac!

**lvbroham1** · 11-25-2006, 08:18 AM

i've had this same problem with my ride. the clunking ended up being the control arm nuts being loose. I thought of everything even replacing shocks. The trick is replace the bushings when tightening them back down, because the time they were loose probably destroyed the bushing.

**dafaic** · 11-25-2006, 09:21 PM

took my mechanic friend out for a ride and he said it sounded like the pinion nut was loose. He felt like the pinion was being pushed in under acceleration and then when force from the engine was taken away the pinion was able to back out just enough to make rear end noise. Well i decided this was easy enough so i jacked the car up as high as i could as i was going to pull the drive shaft and check the bolt. Well i grabbed the back driver tire when i got under the car to reposition my self and the tire wobbled. Checked the other side and it was solid. So I pulled the center cap off and a lug nut fell out. It still had part of the stud in it. Another lug nut was missing and 2 other lug nuts were hand tight. So do the math and you realize only 1 lug nut was holding the tire on. I replaced the wheel stud, got all new lug nits for that side and then checked all the other studs and nuts on the car. The rear passenger was missing a lug as well so i replaced it. I have had the car a month so it's not complete disregard for the car and it's condition but something i haven't got to yet but now its been done and checked my brake life while i was at it. It's funny alot of the what i thought was rear end noise is gone as well.

**camaro322hp** · 12-11-2006, 08:38 AM

big mac - your problem is eerily similar to mine, even the part about the sound being there when i turn left, but not right. i even replaced all the bearings (diff & wheel bearings) as well as both u-joints, and the noise is still there. i took it to my mechanic (f-body knowledgable, owns 2 of his own), and he is stumped. he did all the work for me, and he can't figure out what is causing the noise. have you figured anything out since your post?

below is a copy of my post over at camaroz28.com.

Originally Posted by me at camaroz28.com

my car is a 99 Z28 M6.

anyway, about 2 years ago, i heard a cyclical whining noise coming from my rear end. i took it into my guy, and he found a bad bearing around the pinion seal, as well as bad axle bearings. he replaced the pinion seal bearing, as well as both axles and axle bearings. i had him put 3.73 gears in while he was in there.

up until a couple months ago, all was good. however, recently, i've started hearing a different noise from the rear end. this noise is definitely different from the cyclical whining i heard 2 years ago. this noise is more of a clunking, or a knocking, and it's proportional to the speed of the car.

i took it to the same guy, and he heard the noise while we road-tested. he took the rear end apart, inspected every bearing, and said he couldn't find a problem. all the bearings were good. while he was in there, i had him go ahead and replace every bearing in the rear end, as well as both u-joints on the drive shaft.

after all this work, the noise is still there! what else could it be? what else should i look at?

thanks for any help. this noise is going to put me in the crazy house....

**bigmac776** · 12-14-2006, 05:26 PM

Guys,

I figured my noise out. I'm embarassd to say what it was but for the good of the thread I'll spill the beans. After tearing into my differential about 4 times to find nothing wrong I decided to live with the noise. I also decided to go back to my SLP muffler instead of my Loudmouth. I drive long distances to work and the drone was wearing on me. The next day on my way to work, I was listening to the noise in my quieter surroundings and it suddenly didn't sound like it was coming from the rear. It was in the front. A long story short and 2 wheel hub assemblies later, the noise is gone. It's a beautiful thing to be rid of it. The car rides and sounds so smooth now. It should after all of the new parts I have put in to it. I really missed the diagnosis but I learned from it. I will also say that I couldn't feel anything wrong with the front bearings when I was changing them. But it all made sense that the turn of the steering wheel would make it go away in one direction. I hope this helps. Also, I found the hub assemblies to be the cheapest at Advanced Auto Parts. $114 per side with a 1 yr warranty. I believe Parts America has them for this price as well.