Driveshaft alignment?

[Marcus33]

I'm trying to chase down a low RPM under load vibration since my 5-speed swap.
I replaced the guibo today along with the csb. Upon reinstallation the very low rpm vibration is gone but it's been replaced by a much worse one under load at higher rpms.
I didn't put together the driveshaft the way I had originally done it when I did the 5-speed swap. Previously i had lined up the white dots on either piece. This time a shifted it by 1 tooth, so the u joints align... Was this the wrong thing to do? Could that be the cause of this much worse vibration?

[tomstin]

First, in the Center Support Bearing (CSB) straight and preloaded? Flex disk oriented correctly? Torqued properly? Next, check the alignment of the entire drive line. https://www.r3vlimited.com/board/sho...ight=alignment

[jbontke]

I'm trying to chase down a low RPM under load vibration since my 5-speed swap.
I replaced the guibo today along with the csb. Upon reinstallation the very low rpm vibration is gone but it's been replaced by a much worse one under load at higher rpms.
I didn't put together the driveshaft the way I had originally done it when I did the 5-speed swap. Previously i had lined up the white dots on either piece. This time a shifted it by 1 tooth, so the u joints align... Was this the wrong thing to do? Could that be the cause of this much worse vibration?

The white dots are what the driveshaft is balanced on. BMW balances one part of the drive shaft, then the other end. Then they balance them together and the dots keep that in sync. If they are not lined up, it will be out of balance. How do I know? Learned the hard way myself on an e60.

[Marcus33]

First, in the Center Support Bearing (CSB) straight and preloaded? Flex disk oriented correctly? Torqued properly? Next, check the alignment of the entire drive line. https://www.r3vlimited.com/board/sho...ight=alignment

I think i'm good on all counts.. I noticed my rear subframe bushings were totally shot, and i think i probably made them worse when i had the car on jackstands sitting on subframe.. replacing those tonight.. hopefully it fixes my problems..

[ScottSneed]

The dots are a cool way to see where it's aligned but you should make sure the ujoints are parallel to one another. Also, preload the csb as said earlier.

[ForcedFirebird]

The white dots are what the driveshaft is balanced on. BMW balances one part of the drive shaft, then the other end. Then they balance them together and the dots keep that in sync. If they are not lined up, it will be out of balance. How do I know? Learned the hard way myself on an e60.

The shaft halves are balanced individually on an e30. I have been swapping and mismatching drive shafts for years, it's often easier to find a good rear half than a whole shaft as all the e30 rear sections are the same (318, automatic, manual). As long as the u-joints are square to one another, they run true, but if they are 90° out they will vibrate.


If you look at this pic, you can see how they should be oriented....

https://www.realoem.com/bmw/enUS/showparts?id=1113-USA-01-1991-E30-BMW-325i&diagId=26_0243

e36 and newer shafts are different as they have both u-joints on the rear section, but they can also be swapped around, just have to lay the 3 bolt yoke on a flat surface with two of the tangs touching, then align the u-joints properly. I have even cut the yokes off and welded the larger yoke on shafts for swaps with no ill effects - just did one on an s54 swap at the shop since the owner had a reman'd shaft. Cut the big yoke off an eta shaft, cut the front half of the 318 shaft in half, turned a step on the yoke in a lathe to press fit inside the 318 tube and TIG'd it closed. Car is making several hundred horses through a blower and it's working fine (also did one many years ago for an m20 turbo swapped 2002).