The outer CV boots are the most prone to wear. You should keep an eye on them, because if they split open, the CV joint will sling grease all over the wheelwell, and the dry CV will soon fail (clicking noises while turning). Fortunately, the outer boots are easy to replace. Don't bother with boots sold in cain auto parts places that are split down the side and allow you to change the boot without removing the joint--they don't work. Get the kit (available from most aftermarket vendors) that includes new grease, axle bolt, and circlip. If possible, verify that the axle bolt has threads all the way up to the head.
Here's a list of what you'll need:
Here are the steps for replacement:
Some of the 20V cars came with a center driveshaft made of carbon fiber. No mention of these is made in the Bentley manual, or on the Coupe parts fiche. The main difference that I know of is in the center u-joint. The joint on the standard driveshaft is open and can (should) be lubricated by the process described below. The joint on the carbon fiber driveshafts is sealed and looks like a donut.
NOT for cars with a carbon fiber driveshaft! Look at the connection point, just above where the rear diff is and look in there. Use a flashlight. You will see a small square looking piece that is slightly sticking out in that joint there. On (or in) that square piece is a little hole. Get your can of spray white lithium grease and spray some in there. Refer to section 39.22 of the Bentley manual. It said to do this approx every 10K miles. Most have NEVER been done! It has to be in a certain position to really get at it right.
(Steve Buchholz, Clint Calderwood)
If your center driveshaft bearing goes bad (driveline noise between center and rear diffs), you have three options. Audi says that you have to buy the whole driveshaft for big $$$. Blaufergnugen, or Novatechnik will rebuild it for you for less $$$. Or you can try the following for relatively few $. Be forewarned: The procedure below was performed on an ur-q and 4Kq, so you may have to modify some of the steps.
It seems that the whole carrier assembly is available that includes bearing and the mounting rubber. This is a BMW part (P/N 26 11 1 206 502 has been successfully used on a CQ, P/N 26 12 1 209 532 was used on a 4KSQ). Cost of this part is around $35 from GPR (800-321-5432) and has the advantage of replacing all the mounting rubber although the rubber isn't usually bad. They also have drive shaft CV Joints for $93 each.
Special Tools: Other than metric socket & openend wrenches all you should need is 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 homemade alignment tool (which wasn't used during this procedure).
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. You can get a replacement for the u-joint by measuring the dimensions of the cap & spider. You may not need to replace the u-joint, but be careful with it because it's apparently easy to break the needle bearings if it has to be disassembled.
Bentley's Caveats: Do not bend driveshaft, always store and transport in parallel position. Tie up shafts when removing and installing driveshaft. (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 engage differential lock and block wheel. Tie up [and bag] shaft end. Detach center bearing from body and take out driveshaft. You might want to 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 foreshaft. It was not possible for me to fit an openend 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 preferable to keep the u-joint intact). This was done by removing the spring clips for the cups in the foreshaft yoke and then using a socket as a drift punch to remove the cups. It is probably much more civilized to create a makeshift press using appropriately sized sockets and a bench vise. 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 recommend 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 lubrication of the bearings in the u-joint and scoring on the bearing surface of the spider.
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 foreshaft in a vise to keep it from turning. Once the nut is removed the yoke can be taken off (it is splined to the foreshaft. 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 bearing 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. The original bearing was made by INA with a part number of: 6006RSR The replacement was made by FAG and had a few more numbers on it (at least the box had more numbers): 6006.2RSR.T.C3
Reassembly is the reverse of disassembly, but be very careful when reassembling 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 foreshaft yoke (after reassembling the foreshaft, bearing & housing and foreshaft 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.
NOTE: Driveshaft must be adjusted during installation. The Bentley manual has several pictures and special tools for adjusting the driveshaft during installation. The whole idea of the procedure 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 present.
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