This is in regards to my '89 IROC.

I've been noticing this problem in my car where the rear of the car will make a "thunking" noise, especially when going into some turns. If I stand on the side of the car, behind the rear wheels, and push against the car such that the car shakes from side to side, I can clearly hear what sounds like a metallic rattle coming from underneath the car.

Any ideas what the likely culprit might be? Bad C-clips on the axles? Panhard bushings?

Thanks!

 

Tighten up the bolts on the panhard rod. Same thing on my '89.

 

"thunking" noise hmm i had this problem then i took the dead body out of the trunk all better now.

honestly i really dont know what would cause this a bolt could be loose

 

"thumping" noise when going over bumps is usually a loose or broken upper shock mount on whichever side it's coming from.

"Metallic rattle", especially if it sounds like coins jingling in your pocket, is usually the sway bar end links.

 

I had a "metallic rattle" not so long back. Turned out to be my exhaust muffler banging against the body. Expensive repairs flashed before my eyes before I found out the real culprit!

 

Looks like it could be a lot of things.

For what it's worth, this only started happening after I had to remove and weld my gas tank--which obviously required that the whole rear end be dropped out. I did change the LCA bushings while I had the LCAs out.

Mabye I need to get back down there and tighten everything up. Whenver I'm tightening bolts that go through bushings (i.e. the bolts that hold the LCAs in), I purposely don't tighten down too much on them because it seems like making them too tight could keep them from moving at all.

 

This may sound crazy but if none of the above fixes the problem try lifting the back of the car off the ground by the body and not by the rear. The rear has to hang down to where there isn't alot of preload on the coil springs. Now just take both hands and twist the springs 180 degrees.

My 94 Z-28 clunks just like you described. Sometimes it does it when I just get out of the car. I don't know how it does this from the spring but I can turn the spring and it fixes the problem for about 3 or 4 months then comes back. I'll twist the springs again and same thing happens. I've done this for several years now.

 

For what it's worth, check your trans mount. Broken trans mounts are a very common problem that causes that type of thumping.


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Well, it's definitely not a transmission mount--mine is pretty much new.

After driving my car with the stereo *OFF* for once (what a concept), I'm going to change my description of the sound from a "thump" to a rattle. I know that sounds weird--I wish I had thought of a better word the first time.

Anyway, there is definitely a rattle that comes from the back of the car (trunk area) that is constant as long as the car is moving.

From what I can tell, the whole rear end definitely has some left-to-right play in it. The play becomes very obvious when backing out of my driveway and kicking it into drive: I can feel the whole rear of the car slip a little, accompanied by a loud rattle.

Which is responsible for keeping the axle from moving from side to side: the panhard bar, or the track bar? Also, which is which (I know one attaches to the body of the car)? Whichever bar is responsible for keeping the axle from moving from side to side is probably the one that needs to be tightened.

Thanks

 

Does it rattle when you are driving at a constant speed on cruise and you start to go down a hill or grade? My wifes car is doing that and it's the U-joints. It also does it if you are just cruising through a parking lot. Slop or play in the U-joints will rattle as you describe.

 

the panhard bar is the trackbar.

its called both, and it is responsible for side to side movement of the rear.