Hello Al,

Once the joint has started clunking, there's no way to know how much longer it will last. Generally, steady state (highway) driving is the easiest on the CV joint, as accel and decell put the most stress on it.

If it fails, a few things could happen: If you have a standard, or open differential, you will lose power to the rear wheels, i.e., you're stuck. If you have a limited slip, you'll be able to creep off the road. If the joint gets torn apart, it could destroy the axle or worse.

Regarding difficulty of change: I'm currently in the process of replacing two cv joints on my 944 (pretty much the same thing). Here's my write up:

As I did this last night, the procedures are pretty fresh:

Raise rear or vehicle, support w/jack stands. For this job, I placed the jack stands under the shock mount. This way, the rear suspension is loaded, and the axles are relatively level. I jacked the car from (horror of horrors) the transaxle, with a 2X4X10 piece of wood between the jack and the trans.

Place vehicle in neutral, hand brake off

Using brake clean, or whatever your favorite cleaner is, spray the BOLT HEADS of each CV bolt (there are 6 per side). Spray, rotate the wheel, spray the next bolt, etc. Do this for both CV joints on the axle. If you can, spray liquid wrench on the backside (threads) of the bolts.

You need a 'triple square' / 12 point allen / whatever you call it tool. I have the Lilse brand, which requires you to use a ½" socket on the other end. Snap on makes a socket one. I like the Lisle tool for this because it's longer and that makes it easier to get into the bolt. Seat the tool in the bolt, give a good whack with a hammer. I use a nice ½" drive long flex head ratchet (my favorite tool in the world, bought from The Home Depot for like $20) to loosen the bolt.
The I use an air ratchet to remove it. Repeat for all bolts. Note that I don't remember the size triple square you need, but that Lisle sells all 4 for about $12.

You can now remove the axel assembly.

Once the axle is removed, you can remove the CV joint from the axle. Some people say to keep the orientation of the CV's on the axle the same, others (me included) say to rotate them to even out wear. On my car, the CV joint removal is pretty simple.

Remove the clips on the CV Boots. Slide the boot down away from the CV joint.

Remove the snap ring / circlip from the end with snap ring pliers. Hold the CV joint, smack the axel end with a hammer. Remove CV joint.

Now it's time to disassemble the CV joint. Again, some people think it's important to keep the orientation of the cage, race, and inner thingy (what is that called?) the same, other's don't. Regardless, you have to remove the ball bearings, the outer part of the CV (the race?) the inner metal thing (the cage?) and then you'll have it all apart.

Clean everything very well, dry and inspect. If you see pitting, blueing, galling, or worse, the CV is bad and you need a new one. If the parts look good, you can reassemble, repack with grease, and re-install.

When you reassemble the CV, note that the there are two possible ways for the race to be orientated on the shaft. One way allows for a lot of movement (correct) the other causes the joint to bind (bad).

When you go to put the axel back in the car, make sure that NO grease is on the bolt threads. Get those puppies CLEAN and grease free, other wise they can back out during driving. Kevin Gross doesn't recommend it, but I use some lock tight on the bolts when I re-install it.

In case anyone is still reading by this point. I had some loud banging noises going on with my car. The noise was coming from the drivers side rear. In checking further, the noise appeared to be from the drivers side, inner CV joint. Last night I removed the axle and disassembled both CV's.
The inner one was a real mess. The grease (Swepco) had completely dried out or was cooked from the exhaust heat, and the CV was basically running dry. I have a severe case of blue balls (come on, ball bearings), and the race, cage, and inner metal thing have lots of plastic deformation.

The outer joint looks much better, but is still worn out. The inner thing is pitted, and the cage is also showing some wear.

Time for new CV joints, available for about $85 each at the dealer, with new boots, bolts grease, and clips. Anyone know of a cheaper source?
I don't need the boots. Joints must be Lobro, Reppa (?) or otherwise OEM quality.

Barry Lenoble
lenobleb@symbol.com
89 944 turbo, Alpine White