Back when I was installing this latest round of fueling mods, I touched on the fact that I had found my aluminum guibo completely destroyed.
I had attributed this failure to all the clunking and drivetrain vibration I'd been experiencing in 1st and 2nd gears. While the car was up on stands, I swapped back in the OEM rubber guibo the car came with back in 2008 and torqued everything back in. Keep in mind, I did not drop the mid-pipe portion of the exhaust, nor did I drop the heat shielding above that shields the driveshaft from the elements. When I got the car back on the road to test out the port injection and second Walbro 450, it seemed that most of the problem had been resolved. I could still feel the vibration I was experiencing with the aluminum guibo, but it had become much more manageable.
Over the next few weeks, however, things had gotten worse and most of the vibration had returned in 1st and 2nd gear. In fact, in 1st gear under anything but the lightest of throttle, it sounded like the driveshaft was making contact with metal. I limped the car to my garage, and got the car back on stands again. To my surprise, the guibo was still intact and didn't look ripped in the slightest.
This meant the center support bearing was the next possible failure spot, but getting a clear view of that portion of the driveshaft meant dropping the mid-pipe and heat shielding. At that point, it was obvious the center support bearing was destroyed and the culprit of the harshness I'd been experiencing.
The other obvious issue was that back when I'd dropped the driveshaft to upgrade my clutch/flywheel earlier in the year, I had not paid close enough attention to the orientation and installed it upside down. This was putting the angle of the driveshaft slightly off kilter, and therefore trashing the center support bearing itself, as well as the guibo.
I was disappointed in my dumb mistake, but it's not the first nor the last I'll make while wrenching, and now I know for sure what was causing the issue. I used FCPEuro to pick up a brand new OEM BMW guibo and center support bearing. The lifetime warranty on some of these wear and tear items is valuable in my eyes.
I started at the guibo end of the driveshaft and disconnected those 6 bolts. Most DIYs I reviewed recommended pulling the driveshaft at the differential end, but I did not have the 50mm open end wrench in order to remove the oversized nut. This meant leaving the driveshaft attached at the differential, disconnecting the two bolts securing the center support bearing, and pulling back the rubber boot to expose the splines of the driveshaft.
At this point, you'll want to mark the two ends of the driveshaft so they can be reassembled in the exact same way they were removed. The driveshaft is balanced as a single unit and has weights in certain areas for vibration free driving. From there, a 3 jaw puller made light work of getting the center bearing removed from the driveshaft.
Old parts compared to the new ones.
New guibo on the left, old cracked guibo on the right.
To install the new center support bearing, make sure the old one is installed in the same orientation as the old one. I marked mine just to be sure. I used a pipe that was slightly larger than the driveshaft spline and a rubber mallet to push the bearing up the shaft and into place. A press was not needed.
This time around, I made sure I had the center support bearing properly rotated before bolting it down. This made a huge difference in how the driveshaft sits, and tucks much better up in the tunnel.
Final look at both ends after bolting everything back down properly. When reinstalling the guibo, make sure the arrows on the outer ring are pointing towards a flange. That will ensure everything is oriented properly.
Hopefully this can help someone else avoid this very avoidable problem. At least both of the guibo and center support bearing are considered wear and tear items, so its nice to know there's fresh rubber in there.