Just recently we completed installing the below items into the EFI 135i:
- Wavetrac ATB limited slip differential
-OEM BMW gear fluid
-2 Brand new BMW differential output seals (1 per axel shaft)
- Ferodo DS2500 brake pads
- Motul RBF 600 brake fluid
First up we did the brakes. They came out quickly and easily. The rotors still have life in them so I decided to only swap the pads and fluid. Naturally, I choose the Ferodo DS2500s after having used them in different platforms I knew this pad would be a good choice for balanced street and HPDE/AutoX driving. We made sure to bevel down the edges of the brake pad for smooth initial engagement. This helps to eliminate the noise upon first use. The OEM fluid definitely had to go after having been in the car for some time in favor of the Motul RBF 600 fluid. Its boiling point is resilient enough to withstand high temperatures and provide good feel for the pads, which it does very well.
After the brakes were taken care it was time for the differential. Using the uniquely sized wrench (I believe 52mm), we removed the rear end from the car and sent the differential to Autotech Driveline in Florida. **********s supplied the differential through their installation kit and partnered with Autotech in which they separate the ring gear using CNC machinery. The gear is then machined, tapped and threaded to match up with the Wavetrac differential. The differential is fastened to the new OEM gear using 10 ARP ring gear bolts. After completing the job the differential was then sent back to us for reinstallation back into the car. The only thing to note is the differential needs 2 new seals (BMW Part # 33 10 7 505 605 for my 08 manual 135i) in order to be reinstalled back into the car. I used OEM BMW fluid (filled in Castrol containers from BMW) because that is what was recommended by Wavetrac. You are not limited to only BMW fluid though.
I choose this setup to be able to withstand HPDE aggressive braking and increase rear end track in all situations. It made a massive improvement in all situations requiring rear end grip such as off the line pulls, launches and powering out of low-speed corners! Simply put, the Wavetrac differential is the best improvement I have made. No doubtÖ It is absolutely awesome. Drifting is so much easier now in comparison to the factory open differential. Beforehand I felt I had to use the weight of the car aggressively to be able to get a slide going. In my mind, thatís a slide and not a drift in which you can use the power to get the rear end to rotate. I admit though that due to the increased rear end grip and control gained from the differential the rear end now feels softer. Thatís why I picked up the Powerflex rear subframe inserts in advance, but those have yet to go in.
These pads are definitely up for some abuse. They are super smooth, they engage nicely and I feel you can control the pad pressure really nicely. If you let off the brakes just a bit after approaching a turn hard, the pad will release easily. They dust about the same levels as stock. You canít really expect less from a pad that will withstand higher temperatures, more aggressive use, provide better feel and remain quiet. However, they do make an slightly audible click when go you from forward to reverse, or at a hill, because they tap within the caliper. They do not fit as flawlessly as factory but it is so quiet and hardly noticeable that it doesnít bother me the slightest bit.
Thank you Elliott at **********s for you working with me to get this completed!
Install some last minute bits and hit up Pocono and NJMP!
Here are some pictures:
NOTE: I didn't do Eibach springs as well. They were just in the shot.