Here's to all the naysayers that said it couldn't be done. It may have cost $110 and taken several hours of time, but I think it was well worth it! And as far as I know, I'm the first to have completed this mod in E90Post history (maybe even BMW history)!
The pictures pretty much lay out how I did it, but just as a brief overview: First I ordered the 5 series knob
with the leatherette top from my BMW dealer and then took the original 3 series knob
to a machining shop to be milled down to it's four outter connecting points and then filed it down so the points were rounded. I then grinded out the inner mounting points on the 5 series knob
, roughened the top surface of the 3 series knob
(for better expoy adhesion), and broke off the tabs that connect the leatherette top to the knob
. Then I bought the strongest epoxy I could find (2500PSI holding capability) and bonded the 3 series "guts" to the inside of the 5 series knob
. I then conditioned the leatherette top with Zaino, pressed it into the top of the 5 series knob
(fit snug even without the clips) and finally pressed the completed knob
down into the iDrive
control in the car. I'm very happy with the final product!
Time: 5 hours