wopfe

Just took a spin around the city which I enjoyed a lot, summer is here I think I have a new thing to work on on. When I floor it in any gear its smooth until about 50 MPH...if I floor it in any gear at 50+ MPH the car gives a grinding sound...

I think I noticed the sound also when driving over a big bridge...so It could just be related tot the engine load?

I am afraid it is the transaxle or does it sound familiar tot somebody and is it something else? Hopefully easier

Cheers

'79 euro stick shift 928

19psi

Fan hitting the shroud? Had that happen on an old Corvette when the motor mounts were worn. Only did it under heavy load when the drivetrain would twist from torque.

SteveG

Torque tube bearings? Search here. Hard to diagnose as you can't just put it on a lift and listen to it. Need to eliminate those other things, like the fan shroud. I've heard it in another car and it is between "chatter" and grinding, at least that one sounded that way. And at initial stage, it is intermittent: a particular harmonic had to occur within the drive train or it wouldn't do it. Maybe yours is more advanced. How many miles on car?

wopfe

It has at least 100.000 miles on it, nut probably more (previous owner was not sure about the history)...original fan is still there...

Any tips on how to find out if it is the fan shroud? Take of the belt and test it shortly? Other thoughts? Thx

19psi

If it was making contact, there should be obvious scrape marks on the shroud. A quick 10 second check before moving onto other things like the torque tube.

wopfe

Good one, thanks!

Wisconsin Joe

There will also be obvious marks on the fan blade tips. Usually polished clean and bent just a little.

wopfe

This could be it, check the picture I made a little movie where you can see the the fan looks to have some play, i am going to look into that too...

MainePorsche

If it isn't the fan, one more thing to consider before going to the big job of the TT.
How are your tires ?
I had a dramatic sound and vibration from 65 - 70 mph only. I had flat while in Canada and threw on a used 255 in the rear to get me home. A few days later I thought the worst. When my Potenzas came in the sound/vibration were gone.
Just something to consider.

wopfe

Thought about (front) tires top, their pretty old..thx for the suggestion...

19psi

I think you found your problem.
There's not supposed to be any play and those appear to be scrape marks on the shroud.
I'm guessing you have collapsed motor mounts which caused all the above.

wopfe

I will report back later...this weekend i will work on the fan tot make sure that is causing the noise! Will start reading about the engine mounts

wopfe

Got the fan and clutch off. Question, is this normal:
Shouldn't it be stuck in the bearings?

thx!

wopfe

Got underneath the motormounts, how bad is this? Anybody?


Not sure if this is the cause of the noise, noise seams to stop when goong faster ten 80mph...

SteveG

I can't really tell from the video. If they are original, they can't be very good. If so, you might also want to replace pan gasket while the suspension is out of the way. Best indicator is, does the engine "rock" or pivot when you blip the throttle from idle? Another would be to measure another '79 with good mounts, the distance from a given engine part to the cross brace.