Clunking noise...revisited - need advice

Periokid · 10-28-2001, 04:54 PM

I while back I mentioned a clunking noise when going over certain bumps.

I could not figure it out until I looked at the transmission. A clean spot on the transmission caught my eye and then I figured it out.

Apparently the center of the rear sway bar comes in contact with the center of the transmission. There is a clear mark on both the transmission and sway bar. I placed a peice of rubber on the sway bar just to see if the noise would go away and to my amazement, THE NOISE DID GO AWAY!

Why would this occur? I changed the shocks recently thinking this might be the cause of the noise (and it needed it anyway) but there was no change. I think the mounts for the sway bar are ok but i am not exactly sure what to look for. I certainly can't move it (ie, does not seem loose).

Any suggestions?

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David

1988 911 Carrera Coupe
Leonoff Net

Superman · 10-28-2001, 06:02 PM

That should not happen. The tranny and the sway bar are both bolted to the car frame. They shoudl not move (much) relative to one another. I am thinking that the tranny may be drooping down at times, hitting the sway bar. If so, you have transmission mount issues. Check to make sure the transmission cross-bar and mounts are okay.

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'83 SC

Periokid · 10-28-2001, 06:44 PM

I should mention that when the car is on the lift there is no contact between the bar and the transmission. There is at least a cm of space with the wheels unloaded.

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David

1988 911 Carrera Coupe
Leonoff Net

movin · 10-28-2001, 08:03 PM

It's possible the swaybar was installed upside-down. If done so the trans and bar will be in contact. Sometimes this happens during a clutch job and someone is not mindfull of the proper position.

Superman · 10-28-2001, 08:30 PM

Well, that's probably it then.

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'83 SC

Tim L · 10-29-2001, 05:01 AM

I had a similar clunking noise I thought could be a broken swaybar mount but when I checked the mounts they were OK. I recently removed my engine and transmission and found that the Engine mount carrier was cracked almost completely trough allowing the engine to move. This might be the cause

Tim

Periokid · 10-29-2001, 05:24 AM

Swaybar upside down? Interesting. I'll look into it.

How does one check the engine and transmission mounts?

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David

1988 911 Carrera Coupe
Leonoff Net

Tim L · 10-29-2001, 06:25 AM

On my car all the mounts were OK. It was the carrier that was cracked.

Tim

dtw · 10-29-2001, 06:56 AM

Broken sway bar mounts on the rear are pretty infamous. Have you checked those yet? A friend of mine had a mount break in turn one at Road Atlanta. I was working the corner when it went. Pretty spectacular loss of control. He and the car were shaken but unscathed afterwards. Not as dangerous if you're not driving 10/10ths, but you will still experience lots of understeer if your sway bar is not functioning properly.

Supe's right though- something is not right, these should not be clunking. Sway bar mounts are more common but trans mount failures are not unheard of either. Be careful driving till you diagnose! And good luck..

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Dave
'72 911T to '73 RSR Replica Project

gblumenstock · 11-10-2001, 08:01 PM

I also have this clunking noise in the rear. It is really evident when I hit the "turtles" when making a lane change on the highway. For a short while I suspected the CV joint since the boot was torn. I replaced the boot and repacked the bearing but the noise stayed. I recently have narrowed the clunk to the rear shocks. The rubber at the top of the shock is old and cracked. When I stand on the rear bumper and bounce, the clunk is there. Hahhhh!

I have old Bilsteins on the rear. The shocks seem to damp well. (As observed by more vigorous bouncing) It is almost like the nut on the shock mount is not tightened enough so there is a bit of slack in the shock travel. With my oscillating weight on the car and the rear deck lid open, I can see the "slack" appear as the rubber mount compresses/decompresses and even creates a gap between itself and the body. I tried to tighten the nut following Wayne's instructions for rear shock replacement in 101 Projects but I could not turn the nut without the shock shaft turning.

Any suggestions? Does this really mean that the shocks need replacement? Should I try again to tighten with a vise grip holding the shaft?

GB

Howard Nelson · 11-11-2001, 06:26 AM

How much of a gap is typical between the sway bar and the transmission mount? I have a Weltmeister 22mm in my '72 and it touches the transmission mount even at rest. Does this suggest the transmission is sitting too low? All engine / trans mounts were recently replaced, and the sway bar mounts are solid. Thanks.