I have seen a lot of information that makes this seem like some sort of voo-doo, black box sort of difficult task. But my u-joints went bad, so I did it. And I'm here to tell you it's a piece of cake. And the new u-joints are SOOOO much higher quality than that crap that BMW put in.
First off, you will need new u-joints. You can go to eBay and search for either "e30 u-joint" or "26111105398 meyle" or "26117518304". The last two numbers are the BMW part number used on a number of cars with replaceable u-joints. The listers that show a picture of a u-joint with the retaining clips seem to be delivering a Meyle brand u-joint. It's a genuine German u-joint (that's, um, made in Japan). This u-joint is .070" longer than the original one - probably because the cups are actually machined out of metal and not just some stamped metal cup. Anyhoh, it doesn't matter. It will work better than the original one.
That's the only difficult part - finding the correct replacement part, taking all of the measurements, and making sure it will work. I've done all of that for you!
Now, you know those four little crimps that hold the old u-joint cups in? Yeah, right. Those are just for looks. Pretend they are not there. You'll notice that after the first whack with a good hammer.
You also will want a decent drift punch. I have one that resembles a 3/8" drive extension with the square end twisted off (do you know how I know what one of those looks like?).
One last tool you will need will be a set of dial calipers. You will use the back end of it as a plunge gauge to make sure you have the new u-joint centered.
Now, mark everything with some paint so you can put it all back together in the same orientation and keep your balancing. Put the driveshaft on the ground with one of the cups facing up. Put your punch in the middle of it and give it a good whack. Repeat. After two or three of these, the opposite cup should be bottomed out against the ground. Now, turn it over and do the same thing to the other side. This gets things moving and straightens out those crimps. Now, do the same thing to the other half of the u-joint. If you did the driveshaft part first, you will be working on the yoke part now.
The first part you want to remove is the yoke. The driveshaft will be your handle. If you take the yoke off of the driveshaft with the u-joint still attached to the yoke, you won't have a handle to hold on to when trying to remove the u-joint. So, one cup should be flush with the surface at this point and the other should be sunk-in. Set the driveshaft on the ground with the flush cup facing up and give the driveshaft a couple of good whacks with the hammer. This will shove the other cup down. When it gets flush, set it on a large socket (big enough for the cup to sink in to) and continue whacking until the u-joint bottoms out. Make sure you are hitting the strong, beefy u-joint housing and not the tube it is welded to. Now, flip it over and do the same thing to the other cup. When they are both extended all the way, you will have enough wiggle room to cock the u-joint sideways, catch the edge of a cup, and drive it out the rest of the way. With one cup out, you can separate the u-joint from the yoke. As far as the other cup goes, one whack with the drift punch should take care of that.
After you get the yoke off, you can do the same thing to the driveshaft half. But, instead of whacking the yoke (it's gone), you can put the drift punch against the bare shaft of the u-joint and accomplish the same thing.
Now, it's time to put in the new one. Grab your shiny, new u-joint and pull off two of the cups. Maneuver the u-joint into position and try not to get it dirty. Put one of the cups in one of the holes (from the outside) and slip the u-joint shaft down into it. It won't be in all the way, but just enough to keep the needles from falling out of place while you are beating on things. Hit the driveshaft a few times and drive it down onto the new cup until the new cup is flush with the outside of the driveshaft. Flip it over and put your other cup in place. Whack it until that cup's flush, too. This time, you'll want to hold the u-joint in the center so it holds both sets of needle bearings in place. Once both cups are flush, use your drift punch to countersink the cups until they are about even. Get it somewhere close, but it's not critical. You just don't want it going anywhere at this point. Repeat for the yoke.
Now, use the back end of the dial calipers as a plunge gauge and measure how deep the cups are. place the shallow one up, set your punch on it, and give it a couple of light taps. Measure them again and see how close you are. If you go too far, flip it over and try again from the other side. Keep going back and forth until you get it to within about .005". Now, go to the other half of the u-joint and do the same thing. If you started with the yoke, do the driveshaft now. Once they are both centered, the u-joint should be kind of tight. One cup will be a little deeper than the other (nobody is perfect). Place the deeper one face down on the ground and, the same way you removed the old cups, give it a little tap and drive that cup out .002" or .003". The u-joint should now have perfect clearance and have absolutely no binding. Do the same thing with the other half.
Replace the other u-joint the same way and you are good to go! As far as those clips go... The u-joint isn't going anywhere. I made a cutter that I can use to make a groove for the clips, but I doubt I will ever use it unless I get really bored. The first u-joint I put in, I left it tight (I wanted to see if the cups would move). The u-joint bound up and I was getting vibrations. I figured that, if the cups moved, the u-joint would loosen up and the vibration would go away. The vibration didn't go away. It just annoyed me for a few days. I took the driveshaft back out, fixed the tight u-joint, replaced the other one correctly, and life is good. Besides saving about $500.00, I have better u-joints than what BMW put in at the factory.
From <http://www.e30tech.com/forum/showthread.php?t=116979>
