996 C4 Transmission whine - what's the best way to identify?

I've recently acquired a 99 C4, there's a noticeable whine somewhere in the drivetrain (not engine as changes with road speed and not revs). Whines in all gears and if I dip the clutch, the gears seem fine and change nice and smoothly. From what I've read it's pointing to the pinion bearing however is there any way of determining this (or at least ruling other things out) before I send the box away for a new bearing? I'm doubtful it's a wheel bearing noise as doesn't fade in/out with changes in lateral load. And lastly, if it IS the pinion bearing who is best at sorting these? Cheers.

Rule out that it isn't an issue with the aircon. http://911uk.com/viewtopic.php?t=130442&sid=08ecfd0d8b75dae440f79bbe7a4c3d9f

Thanks for the reply, I don't think it's A/C though as the noise is present with the AC/fan off and is related only to road speed not engine RPM.

If the noise disappears when you dip the clutch it could be the first motion shaft if it just whines all the time it may be one of the other big (expensive) bearings. There is a cheaper bearing available the same spec as the Porsche one, I can't remember which bearing off the top of my head. Most people go to Sports and Classic for their gearbox rebuild but there may be a wait as they get very busy. The tonnage to get the gears off is around 40-50 ton so it needs to be someone who knows what they are doing.

Thanks infrasilver, I've just sent them an email.

Can you give more info on that? Never even heard of the first motion shaft. How is this remedied?

http://www.helicalgearboxes.com/ I got these guys to rebuild my gearbox when the pilot bearing was knackered, very happy with the work they did and would recommend. Also pretty local for you in West Sussex.

It can also be called input or primary shaft. It's a similar noise to when a clutch release bearing goes, not noisy when you dip the clutch pedal, it's usually down to pitted gears on the shaft.

Sound clip and preferably on a twisty country road please . Wheel bearing tends to be load specific so on a right hand it is noisy and a left hand its not .. this isn't set in stone though .. Input shaft bearing and diff bearings are going to be similar .. easy enough to pull the diff and out and inspect .. input shaft and its box out . You really though only need to determine if its a wheel bearing or a box issue as with a gearbox fault it's going to be stripped and checked where as a wheel bearing .. you just replace it .

Re: 996 C4 Transmission whine - what's the best way to ident Is the wife in the car with you? :coat: Could be any number of things. 1st job is identify if said noise is coming from the gearbox. With it being a C4 could easily be any part of the whole drivetrain as noises and vibrations seem to expose themselves in different areas on these cars. Could be something as simple as having the original powerflex gearbox bushes and the sound is amplified through the chassis due to the rigidity of them and it's normal gearbox noises. Also, when was the gearbox oil and front diff oil last changed? A fresh set of oils in both may easily remedy the problem.

Re: 996 C4 Transmission whine - what's the best way to ident Thanks gents, No wife in car, plus she lets me go out and buy these toys without complaint so I'm a very lucky man indeed! I'll get some recording of the noise next time I go out. I only picked up the car on Saturday last service was in Sept last year, I'll check the history re: transmission fluids though. I don't think it's a wheel bearing as it doesn't vary in lateral load and is higher pitched than the typical wheel bearing noise which I'd describe was more of a " deep wobbly rumble", this is more in the tune of "mildly cross cat" kind of whine. Thanks again. M

If you decide to change the GB oil, try removing the filler plug first. Mine needed a breaker bar to shift it!!

Just a thought but as you are only really down the road from me ( i'm in Fishersgate ) you could drop round my place and take me for a drive .. I can give any advice i can then as i would be able to hear it first hand . I can't fix it or even work on it but i can listen and give advise if you want . It would have to be at a weekend though .

That's very kind of you deMort, I'll likely take you up on that although it might need to be after I've changed my suspension (see other post :sad: ) In the meantime, I went for a drive this evening and tried to record the sound with my phone. I've also noticed that it does seem to go when the clutch is depressed (at town speeds anyway) https://youtu.be/bxYJn6Gqwps

My C4 had a whine from the front diff which turned out to be the prop shaft carrier bearing. In the C4 it's in the front diff housing, but easy and cheap to replace. I had the diff out for other work (seals, oil, seized drain plug) so the shop charged ~70€ for the bearing and an hours labor to change it.