[s-cars] UrS4 wheel bearing job

[Robert Rossato]

Duncan,

Not sure if there is an online guide but I'll try to hit the highlights
that I remember from replacing mine a couple of months ago.  I assuming
here that you have, or will be borrowing/renting the proper tool to pull
the bearing in situ.  But you can parse out the bits you need if you're
going to be removing the whole strut assembly and using a press.

Removing the half-shaft can be a bit tricky at times as you have to push
the inner CV joint up into just the right spot to give you enough room
to pull out the other end out of the wheel hub with wheel turned to
complete opposite lock.  After you first separate the inner CV joint
from the drive flange on the transmission, slip a couple of plastic bags
around the inner CV joint to prevent introducing dirt and grime into the
joint as you're pushing up into the engine bay.

Once you have the half-shaft out, you'll need to pull the wheel hub from
the bearing.  You'll need two long M14x1.5 bolts, and a bearing plate of
some sort to drive the bolts against as the wheel bearing housing isn't
large enough to drive the bolts against.  I ended up using two used A4
control arms that my friend had lying around and placed them between the
hub and the bearing housing.  They were thick enough for the bolts I was
using, and more importantly, light enough being aluminum (or aluminium
as the case may be) to hold up easily.  Thread the two bolts opposite
each other into the wheel hub and tighten them up against whatever
you've come up with as a purchase.  Continue to alternately tighten each
bolt to pull the hub out of the bearing.

Once the hub is out you can use the bearing puller to remove the wheel
bearing from the housing.  It is pulled out from the outside of the
housing.  Use the appropriately sized plate to pick up on the outer race
of the bearing to pull it out.  These are large bearings and it takes a
lot of torque to pull them out of the housing using the typical in situ
bearing puller.  You're not going to be able to use just a wrench.
You'll need at least a long 1/2" drive breaker bar, or preferably a 3/4"
drive, with the appropriate socket.

Once you've removed the bearing, clean up the bearing housing of any
rust.  And while the Bentley says not to, I put a thin coating of
anti-seize grease on the housing to make installation of the bearing
easier.  There is an outside and inside to the bearing so note how your
old one came out.  The inner race is split and one side has a smaller ID
than the other.

When you're pressing the bearing into the housing, the plate should push
against the OUTER race of the bearing.  You don't want to load the inner
race.  Once it's fully seated, you'll need to press in the wheel hub
into the bearing.  You'll need a plate at the opposite end that picks up
on the INNER race of the bearing only.  This will prevent you from
loading the inner race against the fixed outer race as you're pressing
the hub in.  Otherwise you'll damage the bearing.

After that you're ready to put your half-shaft back in.  

Torque on the inner CV joint bolts is 59 lb-ft (80 Nm) for 10mm threads,
and 33 lb-ft (45 Nm) for 8mm threads.  I think these cars have 10mm
threads, but can't recall and the Bentley manual and ETKA list both
sizes without specifying which application each is for.  Must have been
a model year change at some point, or it was whatever Hans and Fritz
felt like using.

The axle bolt is torqued to 148 lb-ft (200 Nm) initially, and then
tightened an additional 1/4 turn.

Hope that helps.

Bob




> -----Original Message-----
> From: s-car-list-bounces at audifans.com 
> [mailto:s-car-list-bounces at audifans.com] On Behalf Of Duncan Thomson
> Sent: Thursday, August 13, 2009 4:39 PM
> To: s-car-list at audifans.com
> Subject: [s-cars] UrS4 wheel bearing job
> 
> 
> Hey guys,
> 
> Lining up to do the front wheel bearings on my UrS4 this weekend. Can
> anyone point me to a walk through guide online, or even just 
> the torque
> specs. Don't yet have a Bentley (or even a Haynes) for this car yet.
> 
> Cheers
> Duncan
> 
> p.s. Managed to get the front bearing kits direct from SKF here in New
> Zealand. And they came complete with the replacement bolts, just like
> the dealer kit. With our trade discount, got them from half the dealer
> price. Nice!
> 
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