V70: General Transmisison whine

[grubby mits]

Hi

Its a while since I have posted on the forum - a testament to the reliability of the marque - however I am looking for a bit of advice. I have a 2008 V70 T6 AWD with 113,000 miles on the clock - I have had the car for about 50,000 miles and love it. Recently the transmission has started to whine - at about 40mph and particularly on overrun. I am sure it is not wheel bearings or the g/box, so my thoughts turn to the Haldex system and the transfer box. There is no sign of oil leakage but there is a fair amount of backlash in the prop shaft (engine off). Any advice as to further diagnosis to narrow this down please?

Thanks.

Robbie

[green van man]

I have normally associated such whine as a meshing noise, as in differential backlash between crown wheel and pinion. The problem is that to adjust the backlash you move the gear teeth deeper into mesh, great quiet diff for a little while then the whine is back as when you move the teeth deeper into mesh it is only the tip and root of the teeth you are measuring, these being the relatively unworn areas. They are however a small portion of the load area of the tooth and will wear quickly, hence the whine returns.

There are oil adatives or you could use a thicker oil that will quiet a noisy diff, at least for a while, the ultimate answer is a new crown wheel and pinion along with new bearings but that will be expensive. Another problem here is finding the information you need to rebuild a diff. Pinion bearing preload, differential bearing preload or cap spread and that's a straight forward differential rather than a limited slip where break tourque has to be taken into account. It is doable by a competent person with the right information and a couple of DTIs but as said it's finding the information.

Back in the day I used to rebuild and adjust ford limited slip differentials on rally cars, made a few brackets to hold the DTIs and set preloads with a spring ballence and a known radius, of course no one then was bothered about quiet, not with straight cut gearboxes.

If there is no obvious slack in the joints and you are sure it's diff you may find living with it the cheapest option. Afraid I have no knowlage of the haldex coupling or what a failing one would sound like.

Paul.

[MissSpentYouth]

Hi Robbie,

I have just had the rear differential rebuilt for a customers 2008 volvo v70 T6 AWD with 128K miles which was whining just as you describe. I used Hardy Engineering they are very familiar with this unit I believe it is also used in the free lander were it also causes problems.

The Haldex unit tends to be fine but worth changing the oil and filter whilst its out. The diff will require a new set of bearings the pinion and crown wheel should be fine to reuse.

Its quite a job to get the diff out cant remember how many hours I charged probably about 6 all together.

I think Hardy Engineering charged about £600 to do the reconditioning, they could also fit it for you if you could trek over to Leatherhead

I disconnected the prop shaft at both ends and tied it out of the way then test drove the car to check the noise was gone before pulling the diff as I wanted to be sure it wasn't the gearbox, wheel bearings, tyres etc.

cheers Ben

[grubby mits]

Thanks both for your input. Whilst I am handy with the spanners the Volvo AWD system is beyond my knowledge and from what you say I think I'll leave it to the specialists.

I'll have a word with Hardy Engineering next week and see if they'll confirm the diagnosis and give me a price for the whole job - fortunately I have other transport can leave the car with them for a week or so. Sounds like it won't be cheap, but then again I would rather that than change the car.

I'll post a conclusion when its all done.

Cheers.

Robbie

[grubby mits]

Well, I got the car back today and am very pleased. The problem was confirmed to be the input shaft bearing so I arranged for Hardy Engineering to drop the rear sub frame, dismantle the differential and replace the bearings - and change the Haldex oil and filter whilst they were about it. The transmission is now running beautifully silent again - at a fraction of main dealer prices!

Hardy were great, and I can recommend they be considered for any gearbox or differential work.

Robbie