Joe - Does this sound familiar? See if you can play this .wav file of my clunk when taking off.

 

I remember Joes car having a more metal to metal sound...it will be interesting to hear joes recording next to yours.

 

Can't say it does Steve. I think I hit paydirt with these. Oh, it was 7 times we tried not 4.

http://members.rennlist.com/jserio/P5170285.MOV

http://members.rennlist.com/jserio/P5170286.MOV

 

This is a very very rare movie op of the 405 at 6pm on a weekday with 1) traffic wide open and 2) me doing under the speed limit .

Thought I'd share.

http://members.rennlist.com/jserio/P5170287.MOV

 

I can see I'm going to go running naked and yelling in the streets because this will make me nuts. Okay, after posting my upload I went to the garage, put the car in the air and went to work. Of course the shield covers the tube pretty good but there are peep holes in the front and back so I put an extension in the hole and tapped it lightly and a wrapped it hard. No noise or vibration that I can tell.

NEXT

 

In my case
1. The sound. It came under braking only, not acceleration. I would say I felt it 4? out of 5 times. As explained earlier, (sledge)hammer-like. At the same time I could feel it in the (5-sp) gear lever, but very weak.

2. The investigation.
(a) battery.
Firmly in place as it should be.

(b) exhaust
Nothing was loose.

(c) driveshaft/differential.
Since it was a heavy sound, the initial suspect was the rear axle. There was a small play (3-4 mm?) where the right side drive/half-shaft enters the differential - ie if you pull on the differential connection of it, it moved in and out a bit - and while one person did so, I sat in the car and could clearly feel this movement in the gear lever. However, this amount of play appears normal and within tolerances, so it was regarded non-related to the noise.

(d) axle/torque tube/clutch housing.
No play at all.

(e) rear axle itself.
Took it off. It's hold by 2+1 bolts on each side, total of 6. One of these were in fact broken and had to be drilled out, but still this should not be enough to make the whole axle move!

(f) clutch assembly.
Again, no anomalies found.

(g) torque tube
As explained, knocking as hard as you could with the hand on the rear 2/3 of the tube did produce a metal-to-metal sound, indicating an inside failure. Takin it off and tilting it from side to side, re-produced the heavy sound.
With internals out all made perfect sense: The huge heavy damper had separated from the front rubber-seal failing, making (i) the front metal piece to tilt down and contact with the inner tube housing, and (ii) (I guess this) more and more play eventually causing it to slide back and forth. Again guessing, It clonk'd only when braking because it was the front part that was separated from the seal - the rear seal was still attached to the damper, hence under acceleration the rubber-seal hit the rear bearing (ie rubber-to-rubber). But under braking I assume the (tilting) exposed front-end metal-part of the damper hit against the center bearing, it making the metal-to-metal sound.

The car's not back on the road yet so of course I can not be 100% sure - but I'm pretty darn sure this is the culprit in my case.



ps, maybe an omen, I'm off to Dubai in 5 hours to view a Felsengrun '87 AT for sale, a friend of mine looks at buying it.

 

That's it. The exhaust and shield come down this weekend. I gotta get my hand on it.

 

Just make sure to verify your AT car has a similar TT with a damper inside - not all models do.

 

Hey Kol, How do I go about that? You mean some had them and some didn't?

 

I'm certainly not sure what year/models has the damper, but perhaps Villhuer knows? He's the expert on torque tubes. In one of his posts, quote: I have heard damper being in '88 S4 automatics TT . You might PM him for more information. Also in his post (scroll down) there is a picture of both 5sp and AT damper for 90-91 model years. Maybe all model years have it?

Here's misc online information about tt rebuild;
http://www.nichols.nu/tip814.htm
http://home.comcast.net/~gq-beej/928/ttrebuild.htm

 

just had this same noise diagnosed on my 1989 AT s4. Its the vibration damper in the TT. Very puzzling as the noise was in the front when braking and in the rear when accelerating. We are taking the damper out and replacing the bearings as they have taken a (literal) hammering.

I know that the damper was dropped from the 928CS, does anyone know how this will effect the level of vibration coming from my S4's TT?

thanks

 

I had a metallic noice some times which turned out to be the metall strip between the engineblock and header/exhaust flange.
On my car the bolt at the blockside was missing but I can see yours is there.
Just make sure it is tight, if it is I think Kolbjörn is right about the TT.

Cheers/Peter