Whine on overrun

sco

sco

A2OC Donor
I test drove a TDi 90 today that had a vague whine audible on overrun. Definitely did it in 4th and 5th and seemed road speed dependant rather than engine speed. The seller said the car had had a replacement gearbox recently and that the whine was there before the change. Does this ring any bells with anyone, a search doesn't really find anything similar apart from a wheel bearing but it didn't sound like the rumble I'd normally expect for a failing bearing to me.

The gear change in itself was ok - perhaps a bit more rubbery and notchy than I might have expected and the gear lever was loose but the syncros seemed to work well enough.

Thoughts and suggestions please,

Simon.
 
it's possible it's the diff bearing... but if it's road-speed dependent - and only really happening above 40mph, then I'd assume the wheel bearing is one source. Is *everything* else OK with the car? You'll need to get it on a lift to check the bearings over and the front ones are not a particularly easy fix.

- Bret
 
For it to be the diff, the gearbox you have would have to be the one you exchanged.

The diff is integral to the gearbox and so if you have fitted an exchange gearbox it would be almost impossible to have the same noise,

But if you had your own gearbox reconditioned then this it really could be the diff causing the whine, they would probably not have touched the diff.

Steve B
 
So as its somebody else's car I don't really know the full details on the gearbox - it could have been a complete swap or just taken apart and reconned in which case it could be the diff and they just didn't do a thorough job.

Rest of the car was ok, everything felt taught and rattle free although the brakes were a bit wooden probably from standing. Bodywork was about what I'd expect for a ten year old car - few minor scratches and the odd scuff, alloys were largely unmarked. Interior trim was all good apart from bald climate buttons and a tiny hole in one of the rear seat squabs.

I did wonder if the vgt was seized or coked up - it pulled very strongly up to 2k but then seemed a bit lacking although it revved freely enough. Only I thing I noticed was quite a shudder on start up - was smooth and quiet apart from that though.

Simon.
 
The shudder on start up could well be the Dual Mass Flywheel (DMF) (only used on the TDI 90) but I hope not.

To replace that (and the clutch) cost me £600 and that was heavily discounted.

Steve B
 
At the same time as the gearbox it had a new clutch and dmf so shouldn't be that.

Simon.
 
But at that price I would expect that the gearbox had a warranty of some sort and the diff is an integral part of the gearbox< is it worth checking with them?

Steve B
 
The gearbox had 9 months warranty remaining but I suspect would not be transferrable to a new owner. You are right that it could be worthwhile talking to the garage that did the work to find out exactly what was done but at the end of the day the whine will still be there.

Simon.
 
sco said:
The gearbox had 9 months warranty remaining but I suspect would not be transferrable to a new owner. You are right that it could be worthwhile talking to the garage that did the work to find out exactly what was done but at the end of the day the whine will still be there.

Simon.
Click to expand...

Warrantees on things like that are normally transferrable, a bill of £1,400 should not only cover the car until the owner sells it.

The problem is that they would probably claim that they reconditioned just the gearbox and not diff.

Are you sure it is a whine? Is it high pitched, or low pitched.

The reason I ask is that the A2 is very sensitive to tyre noise (not sure why, perhaps because it is light?)

We have had three A2s that had noise on the overrun, especially when slowing down, one of them even caused vibration that you could feel through the car.

I had the bearings checked and they were fine, we had a slight crunch from the synchro when changing to third (sometimes happens on the A2) so I opted for an exchange gearbox. We fitted that and sent mine back afterwards. The gearbox was fine, but annoyingly the noise and vibrations remained.

I swapped the wheels over from one of our other A2s and was so surprised to find that the noise an vibrations had gone.

Fitted better tyres to the wheels and that was it, it was the tyres!!!

I am now having the same noise on "the project" and it is getting louder. Never when accelerating, only when slowing down (i.e. when the tyres are under load.)

But if yours is a definite high pitched (or reasonably high pitched) whine then it will probably not be the tyres.


A diff whine normally changes when cornering (because the diff is spinning differently) but unfortunately tyre and bearing noise also alters when cornering. But if yours sounds the same when cornering either way, then it could well be a bearing in the gearbox that they didn't replace.

Steve B
 
Agree with the view about warranty. The guarantee is on the part not the owner. Provided you've a receipt and an audit trail of who fitted and or supplied it there 'shouldn't' be a problem.
 
It could be tyres - they were cheapos on the front Contis on the rear. I wouldn't really describe it as high pitched exactly - trouble is one man's high pitch is another man's low pitch! If I had had more time I would have experimented a bit more to confirm whether it was worse with higher overrun torque - thinking back I think it remained when I dipped the clutch so that might point to it not being the gearbox. I'll have a chat to the seller as see if we can interrogate the garage as to what exactly was reconned on the gearbox and if they would honour the warranty across owners.

Thanks for the replies,

Simon.
 
sco said:
It could be tyres - they were cheapos on the front Contis on the rear. I wouldn't really describe it as high pitched exactly - trouble is one man's high pitch is another man's low pitch! If I had had more time I would have experimented a bit more to confirm whether it was worse with higher overrun torque - thinking back I think it remained when I dipped the clutch so that might point to it not being the gearbox. I'll have a chat to the seller as see if we can interrogate the garage as to what exactly was reconned on the gearbox and if they would honour the warranty across owners.

Thanks for the replies,

Simon.
Click to expand...

One way to eliminate the tyres as the cause would be to swap the rears on to the front (in your case). Any difference in the noise would indicate the tyres as a source of at least some of the noise?

Steve B
 
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