If anyone can figure this out... i'll label you a genius!

[derek924s]

I have searched this forum for days and have not found anything resembling the problem I am having. It is an 88' 924S with 150,000 miles. Heres the rundown:

1) There is a rumbling/grumbling noise that is definately coming from the area beneath my feet as I drive. I can only describe it as rolling a bag of stones around on the ground. It is also a muffled sound.

2) It only, and I mean only occurs when I accelerate hard (under load and up hills) or decelerate really quickly. (it is not as noticeable on deceleration).

3) If I am easy on the acceleration, there is no noise at all. There is no hesitation and the car runs smoothly. It will make the sound if I try to ease it up hills (because it is under too much load).

4) It happens in 1st and 2nd gear and is less noticeable in 3rd and almost non existent in 4th. The problem has not occurred in fifth gear at all.

5) There are no clutch related symptoms like the ones people have posted on here such as backlash, metallic noises, and high pitched rumbles. There is no sign of the rubber centered disk having disintegrated. The clutch operates great.

6) It is not speed or rpm related. It does not happen at idle no matter how hard and fast I rev it. It is not speed related because it happens only when I accelerated hard, whether I'm at 20, 40, or 50 mph. It also can happen at 2000 or 4500 rpm. It is more intense in the lower gears.

7) It is definitely drivable. If a little old granny were to drive it (providing she could drive a stick) she would never notice a problem (assuming she wasn't a former race driver). I have been driving it daily and it is of the same severity today as it was on the first day.

This is what I have recently done in the past six months:

New motor mounts (3 weeks ago)
New CV Joints on driver side (last week)
New front wheel bearings (last month)
New belts and rollers (6 months ago)
New swepco gear oil (2 months ago)
New slave cylinder (2 months ago)
New fuel filter (last week)

Just as a side note, the problem happened immediately as I took a test drive after I replaced both motor mounts. I don't know why it happened at that point in time. Maybe it was just coincidence. If anyone has any ideas i would be extremely grateful. Hope this is enough info.

[landrover88]

clutch

[962porsche]

i bet the cat core has come lose from the outter housing . lift and jack stand the car . bang on the cat with your hand like your hitting a volley ball . if it is the catalytic converter and you need to replace it becouse its falling apart then you should change the muffler also . when the cat . starts falling a part all the crap from the cat gets trapped in the muffler .

[rennbay]

Torque tube bearings....

[derek924s]

if it is the cat falling apart , then why would the noise be coming from the footwell? I can literally feel the vibration in my feet as well as hear it. If it was exhaust related I think I wouldn't be able to feel it. I'm leaning towards the torque tube bearings as well, although I don't don't know how to access them. Would it be an easy job? (I'm trying to rule out all causes before I begin to enetrtain the thought of replacing the clutch)

[derek924s]

962porsche, I used to live in branford about two years ago. small world. I live in meriden now.

[krystar]

so it's load based, non rpm related. hmm

torque tube bearing might be a very good possibility. otherwise, u'd still be looking at clutch.

another test to try. jack the car's rear end up and put it on jack stands. with both rear wheels off the ground, start the car and put it in gear. a small rev should reproduce the sound since it's drivetrain related.

[rennbay]

A rumbling noise "felt" from the underside of the car under loading is usually the torque tube bearings. They are indeed a pain to replace and if you can find a good used torque tube in your area it is best just to switch it out.
What area are you in BTW? Maybe I can set you up with somone that has a used one, if that indeed is your problem.

[Flatsixhead]

It's most likely the Torque tube..

[Flatsixhead]

One more thing... If it is the TT - Get one that has been rebuilt properly. It's a big job and you will not want to do it twice.

[962porsche]

i have had 2 of my own 944's with bad bearings in the tork tube . yes you do feal it but they tend to be speed related . the faster the drive shaft spins the more the car shakes . and you tend to feal them starting to go only at higher ground speeds . the cat starts about were your feet are and ends about were the shifter is . i would still bang on the cat before i would rule it out . Branford ? it an ok town . i have lived there most of my life . i moved away then back 5 times .

[John_AZ]

When did you have the rubber clutch disc replaced?

Did you have it done or DIY?

Was the pilot bearing replaced?

Did you replace the TO guide tube?

If you know the answer to these questions, I would guess the TT.

Additional information if interested:
http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/465869-mechanic-says-my-new-torque-tube-will-be-noisy.html
OR
Torque Tube Compatibility for 944s2

GL
John_AZ
1988 924S 60K + 1987 924S 113K DD

[krystar]

Originally Posted by 962porsche

i have had 2 of my own 944's with bad bearings in the tork tube . yes you do feal it but they tend to be speed related . the faster the drive shaft spins the more the car shakes . and you tend to feal them starting to go only at higher ground speeds . the cat starts about were your feet are and ends about were the shifter is . i would still bang on the cat before i would rule it out . Branford ? it an ok town . i have lived there most of my life . i moved away then back 5 times .

why would torq tube be speed related? it should only be rpm related. rpm doesn't get transferred into speed until the tranny.

[924RACR]

Yeah, I'd be expecting torque tube bearings.

[962porsche]

rpm doesn't get transferred into speed until the tranny ????? pushing in the clutch pedal disengages the drive line at and after the clutch . every thing that spins has RPM but then setting at a red light with the clutch in the drive shaft is not spinning this is why i'm referring to it as speed related (ground speed ) and not RPM . i'm not counting out the tork tube ! yes i would check it . i would also check the CV's . along with a half a dozen other things . so insted of trying to split hears try posting some replys that Derek maybe over looking .

[75ohm]

Originally Posted by rennbay

torque tube bearings....

+1

[toolboy62]

Originally Posted by 962porsche

rpm doesn't get transferred into speed until the tranny ????? pushing in the clutch pedal disengages the drive line at and after the clutch . every thing that spins has RPM but then setting at a red light with the clutch in the drive shaft is not spinning this is why i'm referring to it as speed related (ground speed ) and not RPM . i'm not counting out the tork tube ! yes i would check it . i would also check the CV's . along with a half a dozen other things . so insted of trying to split hears try posting some replys that Derek maybe over looking .

yes, the torque tube is spinning at engine RPM not wheel RPM/final drive ratio like a "normal" car. so high engine speed in a low gear can still cause torque tube vibration.

most annoying vibration in my car I finally tracked down to a bad wheel

nate

[bxtech]

I agree with the others here............Most likely it is your torque tube. The bearings inside are failing.

-What happens when you put the car in neutral (when the car is running) and you let up the clutch? Sometimes when the bearings are bad, you can hear the bearings "growl" underneath and then it will go away when you push the clutch back in.

[bxtech]

There was a guy in Crockett, CA that was rebuilding these torque tubes. His name was Pete and the shop was called Porsche and BMW Restoration. I don't know if he still runs the shop. I believe that Partsheaven in Hayward, CA also stocks these rebuilt tubes.

Or............it's been awhile, but I remember there was a member on one of these Porsche forums that showed how to rebuild one of these yourself. They showed how to remove/replace the bearings. They had pictures and all.

[944 Ecology]

We rebuild torque tubes and give a lifetime warranty (mine, not yours).