Gearbox question..

I am currently trying to track down this whining noise in my A2 TDI. The noise stricly follows the road speed and I initially thought it was either a wheel bearing or a CV joint. So today I had the car in the air and checked all four wheels for play, smoothness and noise, but they all moved freely and quiet with no play at all. CV joints all looked and felt good too with only minimal play.

I recently swapped my gearbox to a second hand JDD box, and now I am wondering if its gearbox or differential noise.. The sound is a clear whine, not a rumble og grinding sound, and as mentioned it strictly follows the road speed. And it doesnt matter if the car is in gear or coasting in neutral, the whine stays the same and only goes down as the speed goes down. My knowledge about gearboxes is pretty basic so my question is, can I rule out the gearbox/diff when the whine is also present when coasting in neutral or clutch depressed.? Or are the cogs/diff still moving with the wheels even in neutral and could cause this whining sound.?

Thanks - Alex.

I had something similar a few years back on the GF car. For all the world it sounded like a wheel bearing or CV joint. Changed all manner of things; bearings, gearboxes, CV joints all to no avail. It was only when I put a completely different set of wheels (tyres) on the car that the sound went.

It was caused by having hard Avon ZV3 tyres on that had "50p'd" circumference. Front to back didn't cause a change as they'd all done it. The leading edge of the tyre treads had worn faster than the back so was creating a hum. That's why I never fit avon / hard tyres anymore.

Might not be that, but worth checking as I know how annoying it can be.

Hi

please don't rule out tyre noise.

I have in the past replaced gearboxes only to find the noise remained.

I swapped wheels (for an unrelated reason) and the noise disappeared.

This is worse with cheaper tyres.

The noise matches the speed exactly in neutral and coasting or when decelerating in gear.

So before you spend money on replacing gearboxes. See if you can borrow a different set of wheels to see if that makes any difference. As Dal has said.

Steve B

Thanks for the good advise on tyres.. Today I changed over to my winter wheels to see if that made a difference, but no such luck.. The whining/humming noise is still there, so back to my original question which I hope someone here can help with..

Can the gearbox/diffential still be the cause of the noise when it follows the road speed and is still present when coasting in neutral.?

Thanks - Alex.

motosport said:

Thanks for the good advise on tyres.. Today I changed over to my winter wheels to see if that made a difference, but no such luck.. The whining/humming noise is still there, so back to my original question which I hope someone here can help with..

Can the gearbox/diffential still be the cause of the noise when it follows the road speed and is still present when coasting in neutral.?

Thanks - Alex.

Click to expand...

In short, yes.

I changed my gearbox because the noise was identical to a diff noise, so yes, it does sound like a diff noise that you are describing (Possibly a driveshaft noise too, but that would give a different noise when slowing down on a ben in one direction compared to the same thing while slowing down with the wheel turned the other way (a bit like bearing noises that do that, but you are sure it is not a bearing I think)

Steve B

how did you check the bearings while the car was in the air? The only reliable way I know is to spin the wheel with your hand on the spring... a dodgy bearing will vibrate teh spring, a good one won't.

- Bret

Excellent advice Bret..! I checked by spinning the wheel and listening for any noise and feeling for any loosenes, vibration or resistance, and all four wheels where spinning freely and quiet so thats why I ruled out bearings. But I will try your trick of spinning the wheel with one hand while holding the spring with the other..

It would be great if its only a wheel bearing causing the noise and not the gearbox itself..

Thanks - Alex.

Id go for differential bearings as the diff is always turning even when in neutral , did you change the gearbox oil when you fitted the jdd box , as may help ive done both my A2s and the oil in them was both past there sell by dates, could possibly just be low on oil if youve not even checked oil level is correct

Bret, thank you so much for that very helpful advice.. I was wondering how exactly one could identify a bad wheel bearing, but figured I would be able to either hear or feel it when spinning the wheel. Well not so apparently.. So today I tried again with the car in the air to spin the wheel while holding my fingers on the spring. From inside the car, the noise seemed to come from the front right corner, and sure enough when I spun the front right wheel there was a distinct vibration in the spring..!!

I then tried the other side, and there was a tiny bit of vibration but nothing like the right side.. So it seems like the bearing is the problem after all.. It has been getting increasingly worse and when driving today it was driving me nuts, so now two new SKF wheel bearings are on its way and the noise hopefully soon gone..!!

Once again this great forum comes to rescue and a special thanks to Bret this time..

I will report back when the new bearing are installed..

Alex.

Picked the car up yesterday after having both front bearings replaced with SKF items. And what a difference that made..!! She rolls so quiet and smooth now and all these various whines, rumblings and grinding noises are gone.. My mechanic said the right one was quite bad but the left one still had some life in it, but as always it was a wise decision to replace both..

So problem solved thanks to Brett's great advice and I am a happy A2 owner again..