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Replacing axial bearing (&/or u-joint) on quattro driveshafts

I hear that this post didn't make it before ... and to think I stayed 
late on Friday to make sure it got out for the weekend!  Oh well, let's 
try again!

This post is in response to a direct e-mail from Bruce Bell who 
was wondering about a noise for which the source could not be 
identified.  Since someone else was interested in this info I 
decided to post it to the group.  

A few years ago I had a noise that came from the driveshaft between 
the center to rear diffs.  I found that Audi considers this drive-
shaft a unit and so individual parts are not available for it.  I 
took the driveshaft off the car and found that it was not too dif-
ficult to disassemble and the bearing & u-joint were available from 
non-dealer sources.  This was done on an '83 ur-Q.  I am including 
information from pages 39.42-39.44 of the Audi 4000S, 4000CS and 
Coupe GT Official Factory Repair Manual 1984-87 Including Quattro 
and Quattro Turbo.  Here is a quick rundown of the procedure:

SPECIAL TOOLS: Other than metric socket & open-end wrenches all I 
  needed was one of the 12 point modified hex keys that is needed 
  to remove the socket cap bolts that hold the CV joints to the 
  drive flanges.  Bentley shows a home-made alignment tool (which I
  didn't make).

PARTS NEEDED: It is recommended that the CV joint seals be replaced, 
  these seals go between the CV joint and the drive flange and are 
  available from the dealer.  I don't have part numbers for the bearing
  or u-joint, but the bearing is a standard FAG part.  I was able to
  get a replacement for the u-joint by measuring the dimensions of the 
  cap & spider (This was necessary because I broke one of the needle 
  bearings when I was putting it back together!  BE CAREFUL)

BENTLEY's CAVEATS: Do not bend driveshaft, always store and transport 
  in parallel position.  Tie up shafts when removing and installing 

STEVE'S OPINION OF BENTLEY'S CAVEATS:  If you've got the car up on a 
rack it might be possible for the driveshaft to hang down far enough 
to cause a problem.  If you are working under a car on jack stands all 
that is probably needed is to protect the CV joints from contamination.

DRIVESHAFT, Removing: (From Bentley)
- Detach driveshaft from transmission flange.  Tie up shaft end.  
  [I recommend putting a heavy duty plastic bag (ZipLock) over the end 
  of the CV joint.]
- Detach driveshaft from rear final drive flange.  If necessary en-
  gage differential lock and block wheel.  Tie up [and bag] shaft end.
- Detach center bearing from body and take out driveshaft.

[Installation is the reverse of removal]
NOTE: Driveshaft must be adjusted [during] installation

Tightening torques:
driveshaft/trans. flange       55 Nm(40 ft-lb)
driveshaft/final drive flange  55 Nm(40 ft-lb)
center bearing/body            20 Nm(14 ft-lb)

The Bentley manual has several pictures and special tools for adjust-
ing the driveshaft during installation.  The whole idea of the proce-
dure is to ensure that the two halves of the driveshaft are as co-
linear as possible.  During installation the center bearing housing 
can be adjusted up & down with shims and left and right with slots 
in the mounting holes on the housing.  I marked the bolt locations 
on the housing and installed the same shims that were originally 
test the axial bearing and u-joint at this point to verify that they 
need to be replaced!  The bearing might have a gritty feel as it is 
turned or make noise as the housing is spun as fast as possible.
Now that you've got the driveshaft out you will see that there is a 
nut that holds the fore end of the u-joint yoke to the the fore-shaft.  
It was not possible for me to fit an open-end wrench in there to 
loosen the nut until I had disassembled the u-joint & yoke (but I 
would recommend trying it because it would certainly be preferrable 
to keep the u-joint intact).  This was done by removing the spring 
clips for the cups in the fore-shaft yoke and then using a socket 
as a drift punch to remove the cups.  It should be possible to remove 
the spider from the foreshaft yoke after both cups have been removed, 
but it seems to me that I removed all 4 cups for some reason.  I re-
commend keeping track of which cup attaches to which leg of the spider, 
but that probably doesn't matter since they are machined parts.  
While you're at this point it is possible to check for proper lubri-
cation of the bearings in the u-joint and scoring on the bearing 
surface of the spider.  
ANOTHER AFTERTHOUGHT: I used a mallet and sockets to disassemble the 
u-joint.  It is probably much more civilized to create a makeshift 
press using appropriately sized sockets and a bench vise.
With the u-joint disconnected from the fore yoke it should be possible 
to get a socket in there to loosen the nut.  I held the fore-shaft in a 
vise to keep it from turning.  Once the nut is removed the yoke can be 
taken off (it is splined to the fore-shaft.  You may need to squirt a 
little penetrating lubricant in there to help.  

Once the yoke is removed the axial bearing and housing can be removed 
from the foreshaft.  The bearing was not pressed on, but it did take a 
little work to get it off.  

Looking at the bearing & housing it will be apparent which way the bear-
ing comes out.  It is pressed in, but it isn't too tough to press the 
bearing out with a mallet and something large enough to keep the housing 
stationary (I don't remember, but I probably adjusted the width of the 
vise jaws to be about the OD of the bearing and then used a socket as a 
drift punch (love that Craftsman guarantee :)  It wouldn't be a big deal 
to take the thing to a machine shop to do it right.  The part number for 
the bearing can be read at this point and a suitable replacement procured.
(I'll try to remember to look around this weekend to see if I have the old
bearing laying around for the actual part #, but I think it is long gone)

Reassembly is the reverse of disassembly, but be very careful when reassem-
bling the u-joint.  It is tough to know if one of the needle bearings has 
fallen into the bottom of the cup while you are driving the end caps back 
onto the spider.  As I recall I had to insert the spider into the fore-
shaft yoke (after reassembling the fore-shaft, bearing & housing and fore-
shaft yoke of course!) and then install the cups by hand.  It is probably 
best to use a vise to get the cups inserted as far as possible into the 
yoke (maybe even all the way with the help of a couple of sockets).  Then 
replace the spring clips and you're ready to reinstall the driveshaft in 
the car.  Go ahead and grease the u-joint before installation (service 
interval is 15K miles).  Also remember to clean off the sealing surfaces 
on the CV joint and the mounting flanges and to replace the seals when 
everything goes back together.  

All in all the procedure is not too involved and I'd rather do this than 
change a stupid water pump!  I replaced the bearing on the ur-Q shortly 
after I got the car, and it's given me ~8 years of trouble free service.  
I have tried to be thorough in my description, but feel free to contact 
me if you need further clarification!

Glad to have a chance to help out on the net!
Steve Buchholz

BTW - I didn't get a chance to look up the bearing # last weekend.  Let
me know if anyone would like me to head up a posse.