Clunking/Whirring noise from Rear

[billy mild]

My car is a 1986 944 Turbo. After the car is warmed up and ready to go, if I get on it in lower gears the car will make this kind of clunking/whirring noise. It is way more pronounced while taking turns. Now if I let the car cool off a for a bit and do the same thing it will be okay, but after getting on it for a little bit the sound will come back. So if I do all all highway driving for about 15 minutes and just go WOT while drivnig straight there will be this kind of clunking/crunch type noise, more clunking though, and it id will be repeated clunck,clunk, clunk, ... Once I let the car sit for a while it will be fine.

I have replaced the CV axles with rebuilt ones and there was no difference in change of sound for this.

Could this be a transmission mount or wheel bearings?

[wild man]

Wheel bearing(s), maybe. But probably more likely to be looming ring/pinion failure. How does the gear oil look? How many miles are on the tranny?

[billy mild]

The Transmission was replaced before I got it. This one is supposed to have 60,000 miles on it. It was from Oklahoma foreign.

I had a 924S that had a ring and pinion failure and it never made noises like this. I hope to god its not a R&P problem.

[John_AZ]

Cross your fingers and check the torque on the shocks and muffler mounts. Porsche put out a TSB on this:



GL
John

[billy mild]

I just found out what my issue was. Since someone pointed to the tranny I figured why not just change the oil if I'm going to check it. I checked it and couldn't get my finger wet with oil. So it must have been low. I picked up some valvoline 75w-90 it is meant for GL4 service as well as Hypoid Transaxles. Drained my oil looked a little dark. Put in 2 liters. Checked the level and could feel oil. So I knew it was full. The car no longer makes these noises. I guess it was low on oil. So after replacing my axles and some other stuff, it turned out to be low tranny oil.

Just some info for anyone else who has some problems like mine.

[wild man]

Yup, that's the one thing that everybody (not just porsche drivers) either "forgets" to do, or simply doesn't bother with. It should be changed at 50 and 100K miles, and at every 25K miles thereafter, if you are looking for it to last. And NEVER allow it to get low.

[smokin_944]

+1 wild man. The Porsche shop here didn't even have a clue about the transaxle service. They don't even have it listed...

[billy mild]

This noise is still there. I will post what another person posted on rennlist. I'm trying to see if anyone has any suggestions.

Here is a little more information to help.

Car has a noise in the rear end that sound like wheel bearings grinding. We initially thought it only did it under boost, and with a bad turbo with a chewed up impeller blade, thought the noise might somehow be transmitted through the exhaust from the turbo being out of balance etc. Drive around normally without any hard/sharp actions and you will never hear the noise.

1. Jeff installed new axles, no change

2a. We swapped the turbo for a rebuilt unit since it had to be done. no change

2b. After test driving the car after the turbo swap I had a little more one on one time with it. I could get it to make the noise any time the rear end squated excessively. Hard acceleration, just punching the gas pre boost, hard/sharp slow corners, etc.

3. Figured....classic wheel bearing noise, especially after getting it to do under turning. Pulled the rear brakes apart, pulled the axles, spun the hubs....crunchy. Perfect. Change the wheel bearings on both sides. Noise changed maybe slightly, but still there. Bearing races were grooved significantly.

4. Trans mount does have play in it. Is it excessive? I don't think it is bad enough to make any noises, but who knows.

5. I believe in one of Jeff's post (either here or kcws) he said the transaxle was exremely low on fluid, which he either topped off or changed completely. I wonder if the bearings were starved of lube, but the transmission makes no noise when just driving around normally, braking, etc. Could the diff bearings be loading up under acceleration, making the noise? Not sure. There is some play in the output shafts, but not really enough to make the seals leak, which is usually the first thing to go before you hear any noise. IIRC when he bought the car, the shop that sold it had just installed a used tranny in it.

6. Shocks in the car are definitely shot. It floats like a cadillac. The rear end squats excessively when accelerating, so it needs new shocks all around for sure. Is there geometry out of whack when the car squats, causing the noise?

I hate recommending just throwing parts at a problem, but if it were me, I would get new shocks installed and maybe pull the trans mount and at least inspect it. If the rubber looks toast, urethane it and reinstall it. If the noise is still there after that, then I would swap in another tranny to see if that cures it.

_________________

I would also like to add that I am putting a urethane'd trans mount into the car tomorrow as my mount seems to be soft.

[John_AZ]

"wheel bearings grinding" or like this= small marbels rolling around??

Ring and pinion failure...

You can remove the inspection plate to check.



John

[billy mild]

BTW. My car is a 944 Turbo. I don't think this is a common thing to fail on the turbo transmission.

[Rasta Monsta]

Depends on how it was driven. These Audi boxes don't like clutch dropping, even the Turbo models can blow up the R&P.

[CorsePerVita]

John, that picture makes me cringe. I have developed a sound that sounds like a rattling from the rear. Thinking it had to do with my clutch, after my entire rebuild of TT and clutch replacement, the car was perfectly silent except for this dominant sound (which was MORE audible due to everything else being quiet) in the rear. Sounds like a rattling. Very audible upon decel, or under hard load. Thinking I'll pull my inspection plate and hopefully not cringe. Although I could be low on gear oil. Oddly enough the sound hasn't got worse and has not changed, it has simply stayed the same.

[billy mild]

I replaced the mount with a urethane filled one and there isn't really a difference in noise level. My trans doesn't really move at all now, but no difference in noise. If the R&P was bad wouldn't the car not be drivable.

[looneybin]

i know you mentioned that you replaced the axle shafts, but what about the CV joints??

[billy mild]

Sorry I meant to say I got rebuilt Axles. Meaning the CV's were rebuilt. They were rebuilt by A1 Cardone.

[romad]

turn the stereo up

[billy mild]

Rear end noise.m4a - 1.15MB

Really listen the first 4 seconds. And again at around 14 seconds.

[Aufgeladen944]

Is A1 Cardone the same Cardone that supplies Advance and Autozone with their calipers and axles?

Because...yeah, I would never trust any of my cars with that stuff.

[billy mild]

I got these from AutoZone actually. Do you really think that they could be bad?

[Aufgeladen944]

Yup.

But NAPA's axles aren't any better. It made it about two weeks on my car before it failed catastrophically. That was a fun experience...

I would rule out everything else first but it wouldn't surprise me if the replacement axles are bad as well.