Whirring noise from rear end

[Ralph S3]

Hi All,

My S3 has developed a rather loud whirring noise from the rear end which is proving hard to identify. Its really hard to describe in words but I'll try my best. It is a loudish whirring noise, not a constant noise but it pulses every half second or so. Its definitely from behind the rear seats. Disengaging the clutch has no effect. Its not the rear wheel bearings.

My first thought was the diff but as there is no diff whine or clunk I'm not convinced. Could this be caused by an out of balance prop or a worn prop UJ?

Any ideas.

Ralph

[ChrisGadd]

Could it be the fuel pump on it's way out ?

[ketvrin]

Is it related to road speed ? i.e, does it increase as roadspeed increases? or constant?
is it there all of the time or does it come in at a speed ?
is the noise the same when on the power and on over-run or is one of those worse ? which?
does the noise change when cornering ?

I'm thinking prop-shaft or drive shaft...

K

Edited by ketvrin on Monday 28th September 11:54

[Ralph S3]

Hi,

I going to have another drive tonight to be sure but from memory its related to roadspeed, in that it increases as speed inceases. Its there all of the time and I don't think being on or off power makes any difference. Its definitely does not change when cornering.

It's also not the fuel pump. I'm very familiar with that particular part..!!

R

[ketvrin]

its sounding more like propshaft UJ's to me now...

grease them up and see if the noise reduces. the front one does get hot and does not get much attention due to its location above the exhaust so may just be dry if you are lucky.

removing the propshaft is an interesting experience...

good luck

K

[clarenceboddiger]

Diff bearing?

[mep12345]

ketvrin said:

removing the propshaft is an interesting experience...
K

Only when you do it your way (i.e. the hard way) Kevin. If you are going to take the prop shaft out my site tells you how to do the job in 10 mins + exhaust removal and not getting coated in grease like Kevin is on his website

Must admit though from your discription I would agree with Clarenceboddiger

[GreenV8S]

A damaged CV joint would be my guess. I assume the frequency is increasing with road speed.

[Ralph S3]

Mystery solved. I have made the classic error of assuming that it can't be certain parts as I changed them recently. Turns out its the offside rear wheel bearing again. I only changed it 3000 miles ago so I assume either the hub carrier of hub itself were worn and should have been replaced.

Anyway, I'll take it off at the weekend and have a look.

Thanks for all the guesses.

Ralph

[Barkychoc]

I had the same with a front wheel bearing - it felt very rumbly (hub off the car) and the bearing seat was visibly damaged.
I changed the bearing (a fiver off ebay) and it was exactly the same, and when dismantled again it had grooves in the bearing seat again.
In the end I bought another bearing and thats been fine - I guess I maybe just wasn't careful enough to keep it clean or didn't get it in straight or something when I reassembled it the first time.

[ketvrin]

mep12345 said:

ketvrin said:

removing the propshaft is an interesting experience...
K

Only when you do it your way (i.e. the hard way) Kevin. If you are going to take the prop shaft out my site tells you how to do the job in 10 mins + exhaust removal and not getting coated in grease like Kevin is on his website

I do everything the hard way it seems these days Mark

Glad you found the culprit Ralph

K