924Board.org

MAAS · Joined: 19 Jan 2003 Posts: 72

OK... I have an 87 924S (stick). I've had the car for 2 years now, and I'm pretty much up on all of the major maintenance.

However, about 6 weeks/2 months ago, I noticed a faint "rotational" sound that seemed to be coming from the left rear wheel of the car.

The I immediately assumed that it may be:

1) Bearings

2) Tire probs

At this point, I should stress that this sound is dependent on the speed of the car only, and has nothing to do with what gear I'm in, or whether the clutch is in. Also, it is not CV joints, I know what these sound like, and I had all 4 replaced less than a year ago. I should also stress that this sound is not hugely loud... in fact the average person may not notice it. But I do, since it wasn't there until recently.

I assumed that it may be the bearings. So I took it to my local Porsche mechanic (a very reliable guy). He had it up on the jack, and confirmed that there was some slight bearing noise coming from the right rear wheel.

Fair enough. So he replaced the (slightly) worn bearings on the right rear.

Unfortunately... no improvement.

OK... now to the tires. I had the Michelin Pilots put on about a year ago, so I took the car in to the tire dealer to check the tires and rotate them.

Unfortunately... no improvement. Same faint sound same place. So it's not the tires.

Brakes maybe? But the sound doesn't change when the brakes are applied, nor do the discs feel like they are in any way warpped.

Parking brake? Maybe... but again, no change in sound when I pull on the brake.

OK... so could I be completely wrong about where the sound seems to be coming from? For example, lately my speedometer needle has been more "jumpy" than it used to be. And, come to think of it, the sound does sound a little like a faulty cable. Is there a quick and easy way to disconnect the speedo cable so I can know for sure?

... and any other ideas?

Thanks

-MAS

Techno Duck · Posted: Tue Mar 04, 2003 10:35 am Post subject:

i believe the speedometer runs off the front left tire, so i dont think that could be your problem.
_________________
1987 Zermatt Silver Porsche 924S <-- Sold in Nov. '04
1987 Guards Red Porsche 944 <-- Sold in Jan. '08
1988 Guards Red Porsche 951 <-- Das Boost

Smoothie · Posted: Tue Mar 04, 2003 10:47 am Post subject:

If it's the same as an earlier 924, you take off the front left wheel, remove the little E-clip from the center of the bearing cover and pull the cable out from the other side.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

MAAS · Joined: 19 Jan 2003 Posts: 72

"i believe the speedometer runs off the front left tire, so i dont think that could be your problem"

True... but I didn't think for a moment that the speedo cable was connected anywhere to the rear wheels. The only things that have been making me consider the speedo, is that the sound is somewhat similar, and the speedo started to get more "jumpy" than usual (I think) around the same time.

On the other hand, though... the sound does seem (underline: *seem*) to be coming from the back.

Thanks,

-MAS

AznDrgn · Posted: Tue Mar 04, 2003 11:28 am Post subject:

didn't some of the later 924S's have the speedometer take off from the transmission? I'm not sure, just thought I heard something about that.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

Roger · Joined: 06 Jan 2003 Posts: 1235 Location: Cordova, TN

I doubt its the CV joints they make a clunking noise. Try replacing the tranny fluid. I replaced mine with swepco and my trany noise was decrease quite a bit. Also the sound can travel down the torque tube and sound like its comming from the rear. I do not belive you have a clutch problem but when I heard a clunking noise from the right rear I assumed it was the CV joint. It turned out to be the clutch.
_________________
1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

MAAS · Joined: 19 Jan 2003 Posts: 72

No, it's definitely not the CVs. I know the clicking sounds well, and anyway... I had all of the CV joints replaced fairly recently. This is a much much softer sound, like a tire with uneven tread... which it's not because I had the tires checked and rotated today.

As for the tranny, and/or clutch... pretty unlikely, since the noise is dependent on the wheel speed and has nothing to do with the engine rpms/what gear I'm in/and whether the clutch is in or out.

(Oh, and the clutch is fairly new too... about 2 years... works perfectly)

Thanks for the feedback anyway

Anymore ideas?

-MAS

Techno Duck · Posted: Tue Mar 04, 2003 2:17 pm Post subject:

curious, what does the mystery noise sound like? I currently have a problem with my front left wheel. I believe it is a problem with my brakes as the noise will get faster as the car accelerates, and goes away as i depress the brake pedal. I believe there is something wrong with either the brake rotor, or the pads. havent had a chance to take it apart yet (its a very chilly 10 degrees here!). But to describe the sound, its like a scraping almost. It does however go away after about 15 seconds after accleration. Its not loud, but is noticable from inside the car with the radio on (not blasting, but at a reasonable volume).
_________________
1987 Zermatt Silver Porsche 924S <-- Sold in Nov. '04
1987 Guards Red Porsche 944 <-- Sold in Jan. '08
1988 Guards Red Porsche 951 <-- Das Boost

MAAS · Joined: 19 Jan 2003 Posts: 72

Yes... well, that sounds like a brake problem alright. The problem with my car is that the sound seems to have nothing to do with the brakes. I've tested this on a quiet road, and there is no difference no matter what position the brake pedal (nor handbrake either) is in. Also, I've driven many cars with disc brake problems, especially ones with slightly warped rotors, etc. So I'm familiar with that sound.

The problem is that it sounds exactly like either:

1) bearings, or

2) Uneven tire wear

But both of these have been eliminated.

I guess I could describe the sound as a kind of soft "Shhh... shhh... shhh" sound.

-MAS

crazyinkc · Joined: 10 Nov 2002 Posts: 226 Location: Olathe KS

Just a thought, check the final drive for wear. I sounds like you might have some worn spider gears, maybe ring and pinion. Drain transaxle and look to see if the lube has a greyness to it or some metal debris in it.

Lizard · Posted: Wed Mar 05, 2003 2:16 am Post subject:

I was going to say check the tranny fluid but someone beat me to it, but I would also say take out the speedo cable and drive around the block and the noises in the car bounce really well and can be misleading, and yah pull off front left tire undo circlip and pull cable out the back and tie it up and out of the way, the plug the holes so no dirt gets in, as for the speedo jumping does your odometer work cause it could be the gear that drives the odometer that is skipping
_________________
3 928s,

924man · Joined: 29 Nov 2002 Posts: 25 Location: springfield ohio

My 2 cents: I had a real light noise in the rear and it sounded as if it was to much back lash in the diff. gears, I retorked the big nuts on the axles and the car sounds like I put a new rear end in. Chris
_________________
924 man and luv it

MAAS · Joined: 19 Jan 2003 Posts: 72

Update:

[I should stress that this is not by any means a loud sound... in fact, a passenger may not notice it... and it's certainly completely inaudible with any window slighly open]

I earlier this week I had a full 4 wheel alignment done on the car (it turned out that it needed it). Anyway, still the light noise... but, over the last couple of days it seems to be getting quieter, and sometimes inaudible. I'm wondering if alignment problems maybe caused some slight uneven tire wear... and that now the correct alignment is perhaps slowly "evening out" any small irregularities with the tires.

However, last night the roads were very wet, and the sound was slightly audible again. This would seem to indicate a tire contact sound of some kind, I think???

Anyway, one of the alignment guys suggested that it may be one of the output shaft bearings in the gearbox. The only problem with this is that to know for sure, they'd have to take apart the gearbox. Not something I 'm too keen on at this stage. Also, he may have been hearing the normal 924/944 gearbox drivedshaft/gearbox sounds that I'm only too familiar with (for the record, I've never had any problems with the gearbox... shifting is smooth and solid)

-MAS

MAAS · Joined: 19 Jan 2003 Posts: 72

"My 2 cents: I had a real light noise in the rear and it sounded as if it was to much back lash in the diff. gears, I retorked the big nuts on the axles and the car sounds like I put a new rear end in."

I might give that a try.

-MAS