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Audi A8 Noise

  #1  
Old 07-12-2010, 07:06 AM
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Default Audi A8 Noise

Hi Guys,
Recently bought A8 1997 (D2) Sport Auto, when bought all seemed fine the drive from Brighton to Bedfordshire was all ok, slight whirring noise but was told it was a wheel bearing. Got it home and gave it a good wash as it hadn't even been cleaned for viewing (Just thought they were being lazy).
Anyway next day on the way to mother in laws (about 100 mile journey) the noise got louder and suddenly it went into "Limp home Mode". and all the PRND12345 lit up. we turned round and went home. Upon investigation we noticed a wet passenger footwell, (Now we know why they didn't was it) pulled up the carpet and found lots of electrics, dried it all out over a few days and booked it in to be diagnosed.
20 faults cleared all electrical, 5 came back.
1236 - Shift Lock Solenoid - N110
526 - Brake Light Switch, Incorrect Signal
1196 - Engine/Transmission CAN BUS
1044 - Transmission Control Module Incorrectly Coded
293 - Multifunction Transmission Range Switch Malfunction (PRNDL Input) F125
We have changed a few bits that needed doing to the car i.e. CV Joint, Drive shaft, Flange shaft Oil seal. The car has been driven and it hasn't gone back into "Limp home Mode" (YET)
But my question is, this whirring noise is coming from somewhere, but where?
We originally thought the transmission oil and filter needed changing or that the gearbox was pooped, but on a very steep hill we put it in nuetral and let it rolldown, the noise was still there so surely this rules out Gearbox etc, do you think maybe the Torque Convertor, if so is this gonna be expensive. got lots of other questions but seems pointless asking them at the mo as the car may well go to AUDI HEAVEN at this rate


Any help or insite would be very much appreciated.
 
  #2  
Old 07-12-2010, 10:24 PM
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Even in neutral coasting, all 3 differential gear boxes are still turning. The same is true of many of the internal transmission parts...the trans in neutral is just not connected to the motor, but IS still mechanically connected to the road...from wheels through axles & driveshaft to trans.

A dry, under-lubricated or previously damaged (from lack of oil) differential or a bad bearing in the trans definitely can make a sound any time the car is rolling...in or out of gear....even on a 2 wheel drive with only 1 differential.

An incorrectly installed or unbalanced driveshaft can produce noise or vibration....it turns any time the car is rolling also.

A bad wheel bearing or bad tire should get louder or quieter during alternating side loads...turning left or right.

As for the original water leak, you may already know that's a clogged drain in your fresh air plenum under the hood (bonnet) AND very likely clogged AC drains inside the passenger compartment:

http://www.audipages.com/Tech_Articl...tordrains.html
 

Last edited by silverd2; 07-12-2010 at 10:58 PM.
  #3  
Old 07-13-2010, 04:57 AM
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Hi Silverd2
Thanks for the input, the drains were heavily clogged with leaves etc, we cleared them and [put a hose over the car to see if any more leaks occured, (Non yet) so hopefully that part is sorted now. The noise does sound like a dry, almost knocking noise, which to me sounds like its bad news, what would you suggest?
The Wheel bearing and the C.V Joint etc were changed to see if the noise went but it didn't so I doubt its any of them. We did notice that the diff oil was leaking so we bought some more oil and a seal, changed both, the oil was black and we only got 300mls if that out of it, how much should be in there, Audi said it takes a litre, but there is noway it will hold that, can you overfill the diff, (we only put in about 500mls untill it came out the fill hole.)
 
  #4  
Old 07-13-2010, 02:43 PM
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Posts: 624
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Bentley manual says 880ml in the center diff, with "new" fill. Just draining (no disassembly) might not empty it completely (?)....not sure. It also recommends a short drive and recheck after drain and refill, to assure that the "Torsen" box inside completely refilled. Overflowing out the fill hole is definitely correct, with level car. Overfilling would only be possible if car was leaned off level away from the fill hole....and, to my knowledge, a slight overfill should not cause a problem...the center diff is all mechanical.

As for the next move...?? That's tough. I'd try to isolate the location any way I could. Coasting next to a wall (something to reflect sound) with windows open, to find if it's audible outside the car....front or rear(?) ...Left or right (if either).
Car on a garage lift or jack stands, with wheels free and engine running with transmission in drive, ease on to gas pedal (if needed) to reproduce noise if possible and locate from underneath...if it's audible outside the car.

Hard to say more without actually driving the car(?).

Hope this helps and would like to hear an update, if you learn more.
 

Last edited by silverd2; 07-13-2010 at 09:22 PM.
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