After doing some research I learned that the E9x M3 paddle shifters are completely plug and play for the 135i/335i steptronic transmission. I never liked how the OEM paddles functioned, so once I found a pair of M3 paddles I had to jump on them!
This is a great link to help with removing the airbag and steering wheel trim, but I will include my own set of instructions as well!
http://www.1addicts.com/forums/showthread.php?t=221880
**I removed the negative cable from the battery before starting this DIY. I would suggest you do the same**
The first thing you're going to want to do is look at the back of the wheel and you'll see a hole where a T20 Torx bit goes. This will loosen the steering wheel trim. You'll also have to feel around for a small indentation on the wheel, this is where you will remove the airbag. You'll want to use a flat head screwdriver and insert it into the indentation until you feel a spring-like resistance. Push against the resistance while also pulling the airbag away from the steering wheel.
Left side:
Right side:
There will also be a third T20 Torx you'll want to loosen to remove the steering wheel trim.
Once I removed airbag I placed it on top of the steering wheel like this:
You'll want to grab the T20 again and remove one bolt holding the paddle shift assembly to the back of the steering wheel. One for each paddle shifter assembly.
The next step would be to pull the steering wheel trim away from the steering wheel, it's snugly in the wheel so you'll have to use a little bit of force to get it out. You can then unplug the paddle shifter wires from the back of the steering wheel trim/multi function buttons.
This is where the paddle shifter wire plugs into the back of the steering wheel trim/multi function buttons. Once unplugged, you can remove the not-so-exciting paddle shifters from the wheel.
Now you can install the M3 paddles onto the wheel!
Plug the M3 paddle wires into the back of the steering wheel trim/multi function buttons.
Now you can re-install the steering wheel trim and tighten the (3) T20 Torx screws securing the trim to the wheel.
Snap the airbag into the steering wheel and you are done!
Total time was about 20 minutes for this project
Please feel free to comment with any questions or comments!
- Chris