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D2 - Axles, Brakes, Suspension and Steering Brakes, Springs, shocks, steering racks, steering columns, suspension arms, wheel hubs etc.

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  #1  
Old 26th May 2023, 06:11 PM
strummagnet strummagnet is offline
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Jumping in here. I am looking to replace front and rear bearings as noticed a low whining sound apparently emitting from the rear of the car which after 400ish miles has manifest into a not so low grumble sound (speed related) which is apparent as soon as you go over 20mph - which I can no longer discern whether it is the front or the rear.

Looking online the bearings for cars with 20" rims appear to be different front to back?

S8 Wheel bearings:

For the front: 4F0598625A - For cars with 20 inch rims

For the rear: 4D0407625D

You guys concur?
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Old 26th May 2023, 08:25 PM
MikkiJayne MikkiJayne is offline
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Yes, the 20" front bearing is larger.
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Old 13th June 2023, 12:04 PM
strummagnet strummagnet is offline
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Ok. Got to work on the suspected nearside rear. After jacking up checked the wheel for any discernable movement, none detected. Spun the wheel, no grindy bearing noises noticed either. Removed wheel, brake and discs and used a bar to try and detect movement. None noted. The bearing 'appears' ok.

So jacked up all four corners, and checked for movement noisy bearings. None noted. Im flumoxed. Do i need to go further to investigate a dodgy bearing? Odd as when driving the car yesterday (quick and failed trip to Halfords) the noise getting worse.
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Old 13th June 2023, 12:24 PM
MikkiJayne MikkiJayne is offline
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Next step then is to loosen the hub bolt on the suspect corner and see if the bearing is noisy once its no longer constrained by the bolt. I had the same problem on Lucy's TT a while back - a horrible howling on the left but with the car intact I couldn't feel or hear anything. As soon as I loosened the bearing it was obvious.
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Old 13th June 2023, 01:13 PM
strummagnet strummagnet is offline
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Quote:
Originally Posted by MikkiJayne View Post
Next step then is to loosen the hub bolt on the suspect corner and see if the bearing is noisy once its no longer constrained by the bolt. I had the same problem on Lucy's TT a while back - a horrible howling on the left but with the car intact I couldn't feel or hear anything. As soon as I loosened the bearing it was obvious.
Do you mean the big uber bolt on the driveshaft?
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Old 13th June 2023, 02:32 PM
MikkiJayne MikkiJayne is offline
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Yes. You'll need a 17mm allen / hex socket and a very long breaker bar, which you'd need to change the bearing anyway.

Torque on these things is something mad like 200Nm + 180°. I've never managed the 180° though - my 900mm bar is bending before it gets there, but that seems to be sufficient since I don't have any problems with them coming loose. Also they are supposed to be stretch bolts, but I reuse them a couple of times without any problems. Decent bearing kits come with new bolts.

I stick a few wheel bolts in the disc and then the handbrake should hold it enough to loosen the big bolt.
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Old 13th June 2023, 03:09 PM
strummagnet strummagnet is offline
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Quote:
Originally Posted by MikkiJayne View Post
Yes. You'll need a 17mm allen / hex socket and a very long breaker bar, which you'd need to change the bearing anyway.
I found out I needed a 17mm, much to my surprise as on my old A8 2.8QS I bought a 19mm specifically for the fronts, and that car was a 2002 model supplied with 20inch rims from factory. Strange?

Anyway, breaker and 17mm hex socket and bolt released with wheel on the ground. lifted with the trusty 'widow maker' and wheels checked for bearing noise and wiggled north to south and east to west. Found the dodgy bearing but not the one my ears thought it was (nearside rear) it was actually offside front!!

There is either something very wrong with my hearing or a shift in the space time continuum, it's nuts. I was convinced (well at first) the sound was coming from the rear.
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