I had this knocking sound coming from suspension for a long time now... Recently it got worse - now it knocks even on pretty straight and flat road, not to mention bumpy roads... I (and as a matter of fact also friend who drove my car) hear the knocks coming from the rear, driver side area of the car. For a moment I tought the noise comes from the front end (it does knock a bit when you push the front of the car side to side and I've found out the top strut mounts have some excessive play. Everything else in the front suspension and steering seems nice and tight - checked with the car lifted and 'shaked' by the 'shaker' machine (I don't know how it's called in English). I had the rear end checked on the same machine and it does knock but when you under the car you can hear the knocks high on the passenger side - mechanic suggested to check the things in the trunk (I tightened the spare wheel and all the things in the right rear quarter but it still knocks). We also found out that panhard rod had some play on the drivers side.

Things I replaced recently:
- rear swaybar mounts and endlinks (I think it got worse after the replacement, although I must admit I've performed some fast, hard turns after the replacement, to check if everything is in order).

- panhard rod (I've replaced it today with another one. The "new" one had factory bushings as well (in a bit better condition) unfortunatelly, I couldn't replace the bushings as well, at this time).

Things I suspect (I don't want to suggest anything though):
- The rubber "gaskets" over the springs?
- Springs (cracked?)
- Top rear shock mounts?
- Loose axle (broken axle bearing)?

This knocking 'sensation' takes all my driving pleasure away ;/

 

Im not 100% sure of what it is.....but i had a knocking noise in rear as well adn it turned out that an exhaust mount had broken and my exhaust was sitting on rear sway bar causing all the noise....check it out...if exhaust is laying on there it may be that....good luck
-Troy

 

The exhaust mount (rubber block) is pretty loose but nah, exhaust isn't touching anything - and I'm sure it's not causing these noise...

Thanks for reply though...

 

I would take the shocks off and take it for a short test drive just to see if the noise goes away.. .you may even figure it out just by removing them. check all bolt holse to make sure they're not egged out, if so check the bolt for wear..

 

Does the sound vary with suspension ride height? Get worse as it digs under acceleration? I've seen pinion yokes knock against the exhaust only when the rear dropped. Be more specific.

 

Nope, it knocks all the time, it doesn't really matter if I'm accelerating hard or not, but when I push gas pedal slightly I have a single 'knock' (on the bumpy road it's series of knocks). Those knocks are not loud, but I actually can feel some of them "through" the floorboard...

I have ES polyurethane mounts under the motor and transmission, so there is very little twist etc. there. Last year I tought this knocking (although it wasn't as bad as It's not) was tranny crossmember - one of the threads there was stripped, I fixed it with my friend (rethreaded it and used larger bolt) but it wasn't that and I'm loosing my head now...

I'll check the rear shocks and top rear shock mounts today - I'll also disconnect the swaybar on both sides...

 

Looks like the problem lies in the rear-end itself...

Take a look (small 400KB videos recorded with the mobile phone) and tell me what you think - any input will be welcome:

Right side with the tire in the air:
http://www.astercity.net/~airwolf/02-07-06_1808.avi

Right side with the tire on the ground:
http://www.astercity.net/~airwolf/02-07-06_1812.avi

Left side (it's where I hear this knocking when I'm driving) with the tire on the ground:
http://www.astercity.net/~airwolf/02-07-06_1813.avi

There is some play - on the right side it's like 1-2mm and I guess it's more on the left side.

I think this 'wobbling' can be definately audible as a knocking while In car (I'll check it out later when my friend will be at my place).

So - for now - I decided not to remove the shocks after all...

 

well some of that is just the normal C clip axle, but i wouldnt think it was thatmuch movement. mabe change the diff fluid and look for any chiped Pinion/side gears mabe one of them has a notch that is causeing the rear to bind slightly and what you hear/feel is the gear sliding past that spot.

 

My friends 91Z did the same thing when you move the rear wheels toward and away from you while the car is in the air. I doubt that is what you are hearing but I guess you never know. I suspect it is a bushing somewhere. You might have checked some already, check em all: Panhard bar bushings (2), LCA bushings (4), Torque arm bushing (1), Shock bushings on top under the carpet by the rear seats (4), and swaybar endlink bushings (8). If you hear noise the bushing should be visually worn. Also, how old are the rear shocks themselves? Sometimes if/when they blow out they are known to make odd noises.

 

I talked to my friend last night. He drives '78 TransAm and he told me he has the same issue with his rear-end (but on one side only) - he told when he's driving alone - there is almost no knocking and when he drives with 2 or 3 passengers it knocks like crazy (and that's exactly how it was knocking in my car before it got worse).

Well to be honest - it definately sounds like a bushing. Like a metal touching metal throught the crack in the rubber...

Replaced panhard bar with another panhard bar - still knocks...

That's possible. I'll replace the bushings ASAP. Also one of the LCAs isn't totally straight hmmm

Replaced with the ES polyurethane bushing like 2 months ago...

Yup... I guess I got to check them...

Replaced swaybar endlinks, bushings and swaybar itself (I had another, same diameter swaybar, so I removed rust, painted it etc) 2 weeks ago - and that's when the knocking became more intensive...

I don't know - I have the car for three years now, I didn't replaced them yet. They perform very well - almost like new shocks though and there are no leaks. But I guess I simply have excuse to replace them

 

Swaybar links and worn LCA bushings can do it.

If its not that I'm gonna go worn c-clip and/or pinion bearing/slack.

The sooner you find it, the more stuff you can save when u fix it.

Other dumb one is u-joints.

later
Jeremy

 

I think I will replace LCA bushings ASAP then... One of the LCAs is slightly bent btw.. I have another one, but it need new bushings anyways...

U-Joints were replaced 3 months ago (I've used Precision Super Strength U-Joints and balanced the driveshaft after the replacement - in fact stock U-Joints were almost like new 8) ) - I did that because I have this loud clunk when I shift into drive/reverse (when engine is hot) and some minor clunks while I'm slowing down (downshifts). I tought u-joints gone bad, but it seems problem lies in the rearend (probably pinion bearing/shaft). Transmission has been rebuilded 1,5 year ago so I don't suspect it.

 

Sorry I didnt mean to imply that you should replace everything, just listing some things to check. Usually its hard to diagnose a bushing problem because so much force is required to see how the bushing reacts, but if the bushing is the problem and you're hearing what sounds like metal to metal contact its possible the bushing is worn to the point where you can visually see the problem, or its weak enough to be felt by your fingers. So I would check em out before spending any money.

 

The knocking noise described above is gone (I don't really know what caused it - it just disappeared on it's own), but now instead I have this really loud clunk/knock when I'm driving on the bumpy road (when rear right wheel goes over the curb for example)...

Since the last post in this thread I've replaced all (but a-arm) bushings with polyurethane parts, also replaced front upper strut mounts and bearings...

What you guys think?

PS.: Personally I think it's spring and shock removal time - maybe I'll just check the shock mounts...