Rear End Noises

Topic: Rear End Noises (Read 4624 times) previous topic - next topic

Rear End Noises

October 14, 2018, 12:08:07 AM

My rearend area in my 86 TC is making clunking noises on accel and deccel from a stop, and sometimes bumps. I don't think it is the actual rear end. I put it up and ran it and it seems the like rearend is moving a lot, the front of it seems to move up and down a lot with power and all. Im not sure what's up, I recently replaced the rear end with an 8.8, and used the same stock control arms, and they were fine before I took my 7.5 out, so Im hesitant thinking thats the problem but that is all I can think off.

Any input would be appreciated! Thanks

Rear End Noises

Reply #1 – October 14, 2018, 01:57:53 AM

How are the bushings in the upper and lower control arms? Clunking on Accel and decel could be a lot of different things, but if it's the same noise going over bumps I'd look into all of the bushings and make sure all of the control arm bolts were tight as a first step.

Rear End Noises

Reply #2 – October 14, 2018, 02:32:38 AM

Did you torque the bushings bolts while there was weight on the suspension?

Rear End Noises

Reply #3 – October 14, 2018, 12:30:43 PM

I haven't super checked the bushings, they are the same as before the swap and ran fine, so I didn't think that was the issue. I'll take it apart and look closer soon though. But I jacked up the diff and then torqued them, any different than with it just sitting? And would that cause that much of a problem? Thanks for the responses though

Rear End Noises

Reply #4 – October 14, 2018, 01:54:10 PM

Rear end noises?

There's this stuff called beano, keeps that from happening lol.

No, seriously, what's the gearing in the swapped in rear?

Some folks have reported vibration and noise when they went to 3.73. Though in your case, doesn't seem like it's the problem.

How's the u joints?

Rear End Noises

Reply #5 – October 14, 2018, 01:58:48 PM

It is a 3.73 gear, but it isn't those types of noises it sounds like. It's just when I start going forward or backward, just a clunk really. But the u joints are both new.

Rear End Noises

Reply #6 – October 14, 2018, 04:10:14 PM

Last time I had a clunk on Accel and decel it was my ujoints in my old foxbody, wouldn't happen over bumps though, if we forget about it happening over bumps I would look hard at the u-joints, slipyoke, pinion, could even be a loose ring gear. One thing you could do is have somebody move it forward while you are watching underneath to see if you can see something move excessively with the clunk noise. Just please don't get run over.

Rear End Noises

Reply #7 – October 14, 2018, 07:46:39 PM

If you have access to a shop or garage with a concrete floor, jack it up, put the car up on stands, so the wheels/tires are free and off the ground. Make sure it's safe to be under. Have a friend start it and being sure to hit the brakes between, shift it from drive to reverse and back and forth and see if anything is loose. Again, be safe. A friend of mine died under his Mustang because he was in a hurry and only the jack was holding the car up. Well, it didn't exactly do a good job holding up his car. And neither did his body...

Safety, always time for it.

Rear End Noises

Reply #8 – October 14, 2018, 07:54:44 PM

I had the driveshaft and the rearend both gone through and fixed by a driveline shop, with new ujoints and I can only assume they tightened the ring gear lol, I guess last resort I can check over that. But yeah I've done those both now and can't see anything obviously wrong, It just seems like the rearend is moving up and down more than it's supposed to, so I guess the only thing I can think of would be bushings/control arms. Thanks for the replies

Rear End Noises

Reply #9 – October 15, 2018, 07:39:45 PM

How's the rear shocks?

Rear End Noises

Reply #10 – October 16, 2018, 09:37:55 AM

Wow! There must have been a full moon when I went through the same thing. First I checked backlash. Was at. 012 so I tightened it to. 008. No difference. Replaced the spider gears and cross shaft. No difference. Looked closer and found the poly bushing on the upper arm was shot. I had boxed the uppers and installed poly bushing which I know now that doesn't work on a street car. Removed the plates I used to box the uppers and replaced the bushings. Still clunking.....WTF. I'm now at my wits end. Grabed the driveshaft and gave it a twist. Seemed a lot more than. 008. Pulled the cover AGAIN! Everything looked fine. Checked backlash again and it was all over the board at different spots. Looked closer. Found the problem. Friggin ring gear bolts were finger tight! Years ago when I didn't trust myself to do a gear change, I had a reputable shop do it. Lesson learned.

Rear End Noises

Reply #11 – October 16, 2018, 10:55:42 AM

Rear shocks are brand new.

Rear End Noises

Reply #12 – October 16, 2018, 10:58:28 AM

I had a known rear end shop do mine, but sounds like I'm going to be taking the cover off and checking it out myself. I've heard off shops not having things properly tightened or torqued... I guess that's what I'm checking next. Thanks for the help! I'll let you know if it works out.

Rear End Noises

Reply #13 – October 16, 2018, 04:55:21 PM

If they didn't put fresh lock tight on the ring gear bolts they may have come loose. Usually doesn't happen but sometimes small things like that get over looked in high volume shops just something to look at.

Rear End Noises

Reply #14 – October 16, 2018, 09:12:23 PM

Yeah I will have to see, I'm interested to see what I find when I pop that cover off