It appears that one of the main reasons that older BMWs are scrapped is that their tiny U-joints fail, which often costs ~$1,000 to have replaced!
After reading all of the reports about the impossibility of changing U-joints on BMWs, we (my son and I) decided to give it a try with relatively primitive tools. Our efforts were quite successful, as we have no vibration even at freeway speeds and then some. I thought that I would share our method so that others can fix their own BMW U-joints for ~$20.
The most time consuming part was removing the old U-joint, because there is no way to press it out! Also, you should be careful to support the holders so you don't squeeze them together too hard and distort them. This is how we removed them:
- If you look closely, you'll see that the bearings are "staked" to hold them in place with no possibility of removal. We cut out the stakes with our Dremmel with an abrasive cutoff wheel, cutting into both the bearing and the housing to get it all and then some to make sure that things didn't jam during the following steps. Don't be afraid of making a mess of things, because the extra grooves you cut will HELP at the end of this project! When we got ours apart, we could see that we hadn't gotten all of the stakes, probably adding tons to the pressure we needed to get it apart. Don't forget to mark the relative position of the two bearing holders so you can get them back the way they were when you reassemble things, which will probably help to preserve balance.
- The first bearing we did by supporting the most destroyed bearing with a large enough socket for the bearing to enter it, and hammering on a socket placed on the opposite bearing. While this cannot completely remove the bearing, it can allow it to exit far enough that you can cut a giant X on the end with a Dremmel with an abrasive cutter, jam a large screwdriver in, and pry it out as its sides collapse where they were chewed up by the spider. With luck you can get the whole thing out this way, but all that is really necessary is that you completely expose the end of the spider for removal in the following step.
- Turn the drive shaft over, put a smaller socket onto the end of the spider and the large socket on the opposite bearing and hammer it out as far as it will go. Then, you should be able to remove the spider from the end piece that held the two bearings. Place a socket that is just slightly smaller than the OD of the second bearing onto the inside of holder, attach an extender that passes through the hole you cut in the first bearing, and hammer out the second bearing. Once it is out, if you failed to get the first bearing out in step 1, then just turn the drive shaft over and hammer it out the same way.
- You can do the other two bearings the same way, or you can now "cheat" like we did and simply cut the spider into thirds to remove it, cut the end out of one of the bearings, and proceed as in step 2 above. If you decide to cut the spider, you'll need a mean-business cutoff tool of some sort, because it is hardened steel. We used an angle grinder. Once the spider if out, you'll still need to punch a hole in one of the bearings to pass your extender through to hammer out the opposite bearing, then turn the drive shaft over and remove the bearing with the hole.
- Now you'll want to clean up any of the stakes you failed to remove in step 1, and if the spider has chewed up the housing you may want to get it fixed, e.g. at a machine shop. However, JB Weld probably works as well, just put some of that in there immediately prior to assembly and complete the job before it hardens. However, we just ignored the problem and that also seemed to work!
- Assembly is straightforward. Add LOTS of grease and just press one bearing in a ways, insert the spider into it, press the opposite bearing in a ways, center the spider into both of them, and proceed pressing both bearings in. BE CAREFUL because there is no correcting errors, as you'll have to just cut your mistakes out like you did the old bearings and start over with another new U-joint. We found that the correct position was VERY close to being equally deep on both sides, so use a depth gage and alternatively tap the bearings in until they are both in contact with the spider at about the same depth. Once all bearings are in approximately equal distances ...
- Construct an alignment jig. Ours consisted of a dining room table with the extra leaf in, two egg cartons, and a piece of 2x4 cut into an L shape. Trim the egg cartons to support the drive shaft at the balance points of each segment, so that you can turn it without hitting the balance weights or it wobbling. The L-shaped 2x4 should rest flat on the table, clear the end bolts, and contact the flat machined end of the U-joint, with the top of it being just barely below the top of the machined surface. Attach some masking tape to the top of the 2x4 to write on.
- Now for the fun! Push the 2x4 up against the end of the U-joint assembly to force it into full contact with the 2x4 and mark where the machined protrusion just crosses the top of the 2x4. Note that a small change in height makes a large change in the distance between the two points where the protrusion crosses the top of the 2x4. Check this at several points to establish where the protrusion is high, and hammer on the appropriate bearings while backing up the opposite bearings with something HEAVY to adjust their depth, until you can no longer detect ANY change in the height of the protrusion as you rotate the drive shaft. I estimate that this method can give you approximately 0.005" accuracy, whereas a good drive line lathe can give you maybe 0.002" accuracy. No, egg cartons are not as good as fine machinery, but they ARE good enough for this job.
- Now that it is all back together and aligned, clean up the ends VERY thoroughly to remove all grease, put a drop of Thread Lock on each bearing, followed by a bunch of JB Weld to hold things in place. Set it aside for several hours to harden, rotating it every few minutes to keep the JB Weld from drooping until it hardens sufficiently.
- Give it a day for the JB Weld to harden before you drive it.
If you have any questions, please email us directly as we don't usually monitor this group. Don't forget to remove the NOSPAM from our email address.
Lotsa luck.
Steve and Ed Richfie1d