Originally Posted by marconi118
Remember 2 important things:
as you can see on the pictures, the 335i shaft has a sliding part (to compensate engine and diff movements) that is between the bearing and the gearbox, this means that if the shaft is taken out of the car then the length can vary.
So you have to measure when the 335i shaft is still on the car, or on the car between the bearing mounting hole and the rubber guybo
The M3 shaft has no sliding articulation, the gearbox movements are absorbed by the homocynetic at the diff side
The M3 center bearing puts the shaft 10mm lower than due, very difficult to notice but it is, you will get vibrations at low speed VOT... because the guybo takes a big deflection.
2 solutions: use the 335i bearing, it fits 100% the M3 shaft, or rotate the M3 bearing with the TOP marking facing DOWN and add washers under the fixing bolts to put the axle back in line with the gearbox. no alignment needed with the diff, there is the homocynetic making the job
I tried the m3 bearing up side down and I still found the prop wasn't at the perfect angle coming off the gearbox. Adding washers wouldn't work as the prop needs to get closer to the floor of the car. I've fitted a 335i bearing from the advice you gave me a while ago but have yet to drive my car.
Changing over the prop bearing takes less than an hour, you just need to mark up the prop so it goes back the same way and doesn't need rebalancing.
BTW congrats on getting the swap done.