Rear Thumping

[jasbogart]

Rear Thu;mping

I drive highway miles to and from work in my '94 6 speed, and recently noticed a peculiar noise from the rear end. At highway speeds (50+) there is a noticable thumping coming somewhere from the rear (varies with speed). It goes away under any type of load, it dissappears when under any acceleration, no matter how slight and also dissapears when touching the brakes in the slightest. The only time I hear it is when the car is "coasting". I've been reading some other posts and am leaning towards the possibility that it may be the U-joints (which I believe to be original with 90K miles), but it doesn't seem to meet some of the other criteria I've been looking at. Any thoughts? Thanks in advance.

 

[Eagle85C4]

When was the last time you had the half shaft u-joints checked?

 

[jasbogart]

I haven't yet.....thats one of the first places I was going to start.

 

[Eagle85C4]

Mine did not get to the point of thumping...but what I did notice was that giving it gas and letting off the pedal caused the rear to "wiggle" a bit... Vigman suggested I look at the passenger side half shaft and lo and behold the u-joints were deviod of all the needle bearings and nearly ready to fall out.
It is possible to remove the shaft without taking the whole rear apart as suggested by the manuals. Remove shock, remove nut holding spring on the side and remove the bottom trailing arm. Remove the u-joint caps and gently pry the rear housing away from the car and pull the inside end of the shaft out and up then just remove the outside end and out it comes. Make sure to be careful when removing the joints from the shaft as it is aluminum and easy to scratch, ding and or bend.

 

[vigman]

Dont forget

While your back there... ckeck the rear wheel bearing's too!


Vig!

 

[Da Hawaiian Punch]

Half shaft U-Joints!!! The exact thing happened to mine, I changed the rotors, rear bearings, brake assembly, and pads, still had the problem, my buddy said it was the u-joints from the very begining. I did'nt believe him!! after all that money that I had spent on parts trying to fix the problem!!!!!!!............ I finally listened to him, and sure enough! it was the Half shaft U-joints!!!!! I went a head and changed all the U-joints on the car, theres 6 of them to change out! Hope this helps!!!!!

 

[jasbogart]

The thumping is getting louder and at almost every speed now (as opposed to only on the highway)...my follow up question is this: How long can I wait to do them and what could happen before then? I don't have time to get the U-Joints done right now but I don't want to drive it anymore if something critical could go wrong. If its just a matter of noise and a nervouse feeling then I'll probably wait. Thanks.

 

[dmd]

I found this post while doing a search - five years without a reply, I hope jasbogart hasn't been sitting by his computer waiting patiently all this time!

I hope he checked his lugnuts, because that's probably what was wrong. Been there. Sounds like the wheel was ready to fall off, hope that's not why he never came back.

Dave D

 

[aboatguy]

Wow you dug this up from the dead

 

[bczee]

Check the tires for flat spots, out of round or balance..

I get that thumping after a few laps around the Autocross and if I lock up the tire or spin or anything.. sure thing thump thump all the way home!!

Not sure of your setup, but if they are the same size, you can rotate the tires front to back, that might isolate the noise. Just somehting else to check.