Tired of doing a 1 wheel burn out?
The stock rear differential in both the 135i and 335i is an open differential from the factory. This means you can only put power to the ground on 1 wheel. With an aftermarket rear differential like the Wavetrac, you can now put power down to both wheels!
During a turn, the weight of the car is transferred to the wheels on the outside of the turn. With the weight transferred to the outside, the inside wheel will now have less traction. In an open differential, power is sent to the wheel that has the least amount of traction. This means that if you applied power in mid turn, power would be sent to the inside wheel and thus making it spin and lose traction. With the Wavetrac Limiited Slip Differential (LSD), power is sent equally to both drive wheels giving you the ability to apply power in mid turn. This equates to better traction and thus faster exit speeds out of the corner. As any racer will tell you, exit speed will make a big difference in your lap times. The Wavetrac LSD is what we use on our Time Attack 135i.
Whether you track your car or not, upgrading to the Wavetrac LSD will completely change the dynamic of the car under power. You'll be suprised how much more traction you have, even driving on the street!
For more technical information about the Wavetrac LSD, click here
Early 335i (up to 3/2007) all came with a bolted rear differential. This made it possible to just swap the rear differential to an aftermarket LSD. However, starting 3/2007, BMW started welding the ring gears in the factory rear differential to the differential carrier on both the automatics and manual transmissions. This made it very difficult and expensive to change differentials as you would need to buy a brand new final drive from BMW. Not anymore. Wavetrac is now offering a service to modify your welded factory differential to work with their LSDs. The welded ring gear in welded factory differential is CNC machined and seperated. Once seperated, the ring gear is CNC machined and modified to accept the Wavetrac LSD. Check the chart below to see if you need the installation kit.
Automatics built from 9/2007 changed to a slightly different differential. However, all automatics after 9/2007 are all bolted and thus do not require a installation kit.
All 135i manual transmissions are welded.
All 135i automatic transmission are bolted
How can I tell what the build date is on my car?
There is a sticker on the door jam with the build date.
Model Installation Kit Core Exchange
335i with manual transmission (up to 2/2007) No Not Required
335i with manual transmission (3/2007 to present) Yes Available
335i with automatic transmission (up to 2/2007) No Not Required
335i with automatic transmission (3/2007 to 9/2007) Yes Available
335i with automatic transmission (10/2007 to present) No Not Required 135i with manual tranmission (all) Yes Available
135i with automatic transmission (all) No Not Required
Core exchange program
Installation of any LSD into the rear differential assembly requires a transmission specialist. However, the Wavetrac LSD is now available preinstalled into the rear differential housing. We offer a core exchange program whereas we send you the entire rear differential assembly with the Wavetrac LSD preinstalled into the rear differential housing. It is then ready to be install in your car. You remove your old rear differential assembly and install the new one. This saves you the downtime of shipping your rear differential assembly to us and then waiting for us to send you your rear differential assembly with the Wavetrac LSD installed into the rear differential housing back to you. The $800 core charge is a deposit. Once we receive your rear differential assembly, the core charge is returned back to you. For customers who get their LSD installed at our facility, core charge is waived as your core is exchanged on the spot.
Final Drive Ratio
The rear differential in the manual transmission has a 3.08 final drive. However, the rear differential in the automatic transmission has 3.46 final drive which is a shorter gear ratio. What does a shorter gear ratio mean to you? Faster acceleration. What's the drawback? Lower top speed. The 3.08 final drive gear ratio is good to 194 mph in 6th gear (7,000rpm) which most of the cars won't have enough power to reach that top speed (drag limited). Even if you could, when will you be going 194 mph, even in racing? We are now offering the Wavetrac LSD installed in a brand new automatic rear differential assembly with the 3.46 final drive. This is whe whole rear differential assembly and does not require a core exchange
as you are keeping your old rear differential assembly. This means, you can have the factory rear differential assembly as a spare and therefore can be easily swapped back to stock if you need to. You can also sell the rear differential assembly as a whole without having the need to trade for the rear differential assembly. We run the automatic 3.46 final drive in our 135i Time Attack race car. If you're interested in this, please contact us for more information.
Rear Differential Oil
We use Motul Gear300 75w90 gear oil in our rear differential and is what we recommend. You can also use the factory BMW gear oil as well. Do not use differential oil with an LSD additive.
Pricing for the Wavetrac unit is normally $1,295 for the full differential. However, feel free to pm me or send an inquiry to JohnZhang@EvolutionRacewerks.com
for special pricing for e90post forum members as well as installation combo packages, I will be more than happy to accommodate all your pricing needs!