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Dan1

S3 rear differential BANG!!!! your thoughts please??

Hi all. Please do take the time to read this. Iím not too sure how to kick this one off, but here goes.

Back in May this year my Audi S3 (pre-facelift manual on an 08 Plate) had itís haldex replaced - I donít know if this is relevant.

But jump forward to December and the car has developed the exact same symptoms as when the haldex had gone. Audi have diagnosed the car as the differential that has gone pop this time.

I will try and describe the symptoms for both as they are literally exactly the same:
On off (on for 1 second, off for 1 second) mid pitch humming sound at 30mph, this increases in on off speed as you speed up and the frequency goes up.
It does this at all points of driving mode, braking, accelerating, in gear, out of gear...
When the car would normally get perfect traction if you put your foot down in second, the traction control will light up and it canít put the power down.

I think thatís all of them but if you need to ask any more questions please do. Iím just struggling to understand how I have two sets of issues with both presenting the exact same symptoms.

Really need advice on either a diagnosis or how to present the case forward to Audi if the haldex can play a part.

Thanks for any replies in advance.
Ben H

My technical knowledge on this stuff is pretty much zero! But the fact you say the symptoms are exactly the same might suggest the fault is the same, i.e. Haldex?

You could do with some input from someone who knows their stuff on the Haldex and diffs, unlike me!
BennyBoo

I am the same as Ben.. Not just in name..

I would say though that it's something controling the Haldex, if it can't put the power down and it happens at all points of driving, in gear and out..?

Happy to help! (or not..)
scoobydood

Assume this is covered  by warranty?
dest

Does vagcom show any haldex codes? Might be worth checking with that if you've not already tried it
Dan1

The Haldex is covered by warranty but the rest is not. I'm not 100% sure what happens if the issue has being caused by the driving on a damaged haldex last time (under Audis advice I was ok to drive it!). Should Audi then be responsible for this?
audimad100

do you have written confirmation or something from Audi that states you were ok to drive the car with this type of issue? if you have and the haldex issue first time round has caused a further diff problem then i would say you have Audi by the balls and as said your new haldex will be covered by Audi's 2 year parts warranty
ScottR

Pull your Haldex fuse then go for a test drive. With the Haldex disabled, there won't be any power fed to the rear diff. Might help in the diagnosis.

If it was the diff, would you not expect more noise when turning a sharp turn?
Dan1

We ran a scan and it showed no fault with the haldex. However this doesn't (for me) say that it's defiantly not the haldex as we have had clear misfire and it hasn't shown that before.

It's just so strange how the symptoms a literally identical to last time when it was the haldex.

ScottR, could you tell me where the fuse is for the haldex please?

Also I have acquired the job sheet for the work that was done last time. It's says...
"REPLACED HALDEX IN THE REAR DIFF
AG 055 175 A2 HIGH PERFO £15.39
AN 904 433 01 O-RING ££2.72
A0AV 525 554 F HALDEX COU £891.72"

I don't know if this means anything to anyone? Plus I didn't realise the haldex is located inside the diff itself. Is this true?
Dan1

Just to reply to Audimad100. When the fault came around first time I didn't expect it to be this big of an issue so (like an idiot in hindsight) I didn't get anything in writing as I was just booking the car in over the phone.
dest

Where are you located?
It wouldnt hurt to call in to an Audi specialist for their opinion before Audi rob you blind!
Dan1

I'm in Wakefield/Leeds area. If anyone knows of a really good specialist that's not far away I'm open to taking it there?

That's a scary point, Audi rob you blind. I know some dealerships are bad, but would they really try and have my pants down for this one, and as big as this?
grizz

Dan1 wrote:
We ran a scan and it showed no fault with the haldex. However this doesn't (for me) say that it's defiantly not the haldex as we have had clear misfire and it hasn't shown that before.

It's just so strange how the symptoms a literally identical to last time when it was the haldex.

ScottR, could you tell me where the fuse is for the haldex please?

Also I have acquired the job sheet for the work that was done last time. It's says...
"REPLACED HALDEX IN THE REAR DIFF
AG 055 175 A2 HIGH PERFO £15.39
AN 904 433 01 O-RING ££2.72
A0AV 525 554 F HALDEX COU £891.72"

The heldex unit is bolted to the diff unit not inside the diff unit.

I don't know if this means anything to anyone? Plus I didn't realise the haldex is located inside the diff itself. Is this true?
Dan1

sorry grizz, I noticed you quoted me but there was no message with it?
grizz

The Heldex is not is side the diff unit , it bolts to the front of the unit ..
grizz

The heldex is the silver unit on the left of the photo

Click to download file
Dan1

thanks for the photo grizz, its nice to see what iv been talking about for the last few days. Am i right in thinking the prop shaft comes in from the left and drive will come out the front and rear of the photo?
Byzan a4

I recon its more likely it was misdiagnosed by Audi first time.

Unless they forgot to refill your diff with oil or check it as a minimum ?
Dan1

Finally got the car back from Audi all fixed. Audi paid the lot. Really appreciate all your help and comments.

Thanks everyone!
missmouse

grizz wrote:
The heldex is the silver unit on the left of the photo

Click to download file


Slightly off topic here guys but how can you open a file like this? I get a window saying I have to search the web for a program to open but if I click that I still cant open it! Am I missing something obvious here?
( running Vista)
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