Broken Torque Tube

I have a 1990 S4 automatic with approximately 90K miles. The torque tube snapped when I was on the interstate about a month ago. The mechanic said he had never seen that happen to a 928. He checked with Porsche & they told him in never happens on standards, but automatics develop a "harmonic vibration" that can cause wear to the point that it eventually breaks. This sounds like a manufacturing defect to me & I'm quite disappointed. Anyway, after the car was repaired I noticed a new sound coming from undeneath the passenger side & I feel a vibration in the accelerator when I floor it. Also, when I'm on the interstate (above 80 or 90) it feels as though it doesn't have as much power when I accelerate. The mechanic test drove it with me & said it seemed normal to him. I was wondering if anyone else had a torque tube break on them. I was hoping to get a local owner of a 928 automatic to drive mine & get their feedback. I live in New Orleans & can be reached at 504-376-4270. thanks.

Frank Gordon

Sounds to me like it is out of balance or perhaps the bearings are bad.

Either situation should be the responsibility of the installer, or the rebuilder of the torque tube.

So the TT broke and you had it repaired.

How was it repaired? welding or replaced?

Were new TT bearings installed?
Could it be that a bearing was damaged from incorrect instalation?

When the TT broke were you on the highway or under engine load?
There may be more damage do to the shock of it braking.

Brad

If the shaft broke the shrapnel may have got into a bearing(s).

If the bearings were not replaced they should have been. How are the front and rear flex plates?

There are superior bearings available from a company in florida who also sells the the super clamp. Do all this work and youll never worry about the TT ever again ....

Thats what Im doing this winter as preventative maintenance of a 23YO car.

Surely they put a newly rebuilt torque tube in when they did the work. The vibrations could be as simple as the transmission is not shimmed or aligned properly. It's a simple task that anyone with the workshop manuals should be able to do in less than an hour.