edco

Bill Ball and I have been trying to trace down a rattle in my 88 5 speed. We thought it might be clutch related and with the car showing 140k and no real history we decided to do a clutch job. We replaced everything, the clutch needed attention but was not the cause of my rattle.

The rattle appears when the car is warm and been driven. It’s only noticeable when the clutch is out “Foot Off the Pedal” throw a rev and as the rpm’s fall there is a rattle. It almost sounds like a heat shield rattling but unfortunately that’s not the problem. Once you know what to listen to you realize the rattle is there at idle once the car is warm. Push in the clutch and it’s gone.

Any ideas on where to head from here? Both Bill and I are thinking the torque tube is suspect, but I guess it could also be in the transmission. If you have any ideas on how to approach this pesky rattle please let us know.

original thread

Thanks,

Matt

Mrmerlin

my best guess is the torque tube needs a new set of bearings, otherwise check the clamps on the T/Tube you will need to remove the exhaust and heat shields its not to hard but easy if you have a lift and a helper to lift the exhaust, while the ex is down check the shields for loose rocks also check for anyyhing else that might be contacting the drive line how are the M/Mounts? check these as well

edco

Hey Stan,

The motor mounts look ok, we just had the front pinch bolts off and back on, all looked as it should. I need to take a closer look at the rear pinch bolt, but it looked good as well. The rattle is defiantly something in the driveline or tranny. I guess the main clue here is that you have to drive the car and get the driveline to operating temp before you hear anything.

Bill has offered to help do the TT but I would like to make sure that’s the likely cause rather than troubleshoot with $$$ parts. Both front and rear TT bearings are in the correct location around 9 to 10 inches back.

Bill Ball

The noise is pretty even volume throughout the driveline from the bellhousing to the transmissiton housing. Since we've ruled out the clutch, that leaves the TT and tranny. Neither are doing anything more objectionable than the rattle, so nailing down the source is a problem.

I was thinking of undoing and moving the rear clamp so we could spin the TT w/o the tranny spinning, but Matt pointed out that wouldn't work too well as the rattle only appears after the car warms up. Still I think we should try it. If the rattle is still there, it would indicate the TT is the source.

Any other ideas on how to isolate the source? Maybe we just need to wait until it becomes more obvious.

IcemanG17

I listened to this last weekend at Bills.....my 1st thoughts are TT......since its loudest just off idle when hitting the gas with the tranny in neutral....if the clutch is depressed it doesn't do it (because the TT isn't moving).....another thought I had is some odd kind of resonance from the exhaust or exhaust heat shield.....worth checking out since thats just a loose bolt vs $400+ for a TT..... Either way I'll lend a hand

adam928

Im guessing torque tube bearings...

But i also got a real long shot Its a bit of a crazy thought and might just be jibberish... But I came to think about it when I read that it the sound only appeared when warm...

How does the gearbox oil cooler work? Does it have a thermostat? IF SO... could it be the oil cooler lines on top of the torque tube that has come loose? When gear box become warm... and the oil start to flow through the lines they push against something (tt maybe?) and the noise appears. As I said.. just a long shot...

Bill Ball

Brian and Adam, good idea - we should take a look at things around the TT. We did look at the heatshields, but maybe not close enough. And the items running along and attached to the top of the TT should be looked at. If it were the TT bearings, I would expect more than a mild rattle, although this could be an early stage symptom.

low miler

Absolutely 100% sure it's your torque tube bearings! I've been down this road waaaaaay to many times to not know. And yes, I learned the hard way, Porsche dealership, rattling, heat sheild, no problem........wrong!

If it sounds like a loose heat sheild or catalytic convertor sheild, unfortunately, it isn't. It's your torque tube bearings. Your actually lucky you've made it this far!

Best of luck my friend!

Vilhuer

Its manual gearbox and not a GTS. So no cooler lines. Othervise good idea. I'm not sure if there is thermostat or not but suspect not as oil goes into radiator end tank. One idea behind this is that coolant will heat up gearbox oil more quickly in cold weather. Having thermostat blocking flow to cooler until oil gets warm would be against this idea.

AO

I'm not so sure it's TT. If you're driving down the road at, say, 40MPH and you push the clutch pedal in, while leaving it in gear, does the sound go away? If so, it cannot be the TT because by leaving it in gear, the TT is still spinning, just not at the same speed as the engine. If the sound persists, then you might be right in suspecting the TT.

This is dangerous, but you might try putting the nose of the car against a STRONG wall and the jacking up the rear end and putting it on jack stands. Run the car through the gears and try to recreate the symptoms. Have someone try and listen with a stethoscope to locate the source of the sound.

An exhaust rattle might be the best explanation since it seems to be heat related. That's where I'll put my money.

adam928

Aah... I didnt know the manual cars lacked gearbox oil cooler

Mike Frye

Matt and Bill,

Sorry it turned out not to have been the clutch. I agree that with no history, a new clutch is always a good thing though .

You specifically said 'foot off the clutch' for the noise. With mine, I was getting a rattle only with my foot off the clutch completely, in or out of gear. I sometimes drive with my foot on the clutch pedal, but without depressing it, it wouldn't make noise for me when I did this. I'm not sure from your description, but it sounds like it happens in or out of gear (and at idle once you know what to look for).

I don't remember whether mine only happened when it was warm or all the time, I suspect all the time, so it's probably not the same issue.

I'm going to go against conventional wisdom here and throw one out there since you know my experience level with this (or lack of) and can give it the proper amount of weight . Is there any play in the release arm? I know you said you replaced everything and the release arm bushing is most likely one of these items, but could it be the release arm/ball cup/release bearing alignment that's not quite right? I'm thinking heat may be expanding something just enough to cause a rattle when it's warmed up. With mine it was caused by a worn out bushing, but if something's not lined up right it would leave it loose under some conditions, no?

Or how about that little spring ring that you said gave you trouble? If that's in backward or bent or something would that make a sound?



I'm probably wrong, just throwing it out there for things to consider.

Vilhuer

5sp GTS uses same separate front cooler as automatics.

Courtshark

I had a very similar problem show up in an SPG with a brand new rebuilt transmission. Sounded like gack-gack-gack-gack (fast chattering, and LOUD) under load. This is not Porsche, obviously, so take it FWIW.

Anyway, we went through everything, including replacing the flywheel, pressure plate and clutch. Even removed the whole engine & tranny from the car and went through the box again. We had not done the rebuild ourselves (P/O had just done it befre I bought it). Turned out to be an incorrectly installed chain oiling shield that came into contact with the primary gear chain under heavy load (i.e. clutch all the way out). Compounding the problem was that the rebuilder installed the wrong primary gear for a Saab turbo transmission (easy to do, the differences are minimal between N/A and turbo boxes), giving the chain just enough slack to come into contact with the slightly-too-large oiling shield but only under load. Replaced them both with the correct parts and problem solved. What a HUGE PITA though. I've never been through a Porsche 5spd box, so I've no idea if it has a similar part. This one stumped three Saab master techs for two days.

AO

I almost forgot. When I did my clutch (the 1st time), I about freaked out when I started hearing this tick, tick, tick, well it was more of a scratch than a tick... here, watch the video:
http://members.rennlist.com/andrewmolson/MVI_3140.AVI (might need to right click and Save-As)

Turned out the shaft coupler was rubbing on the head of one of the bolts for the guide tube that had backed out a titch. Those bolts are lock-tighted in now and the sound has never come back.

Edit: Here's that thread....
https://rennlist.com/forums/928-forum/256378-metal-to-metal-scratching-noise-after-clutch-job-now-with-video.html