I recently had my friend (
Engineered Mechanic Mike) do a M3 LSD swap into my 335i. I am a single turbo N54 with 6MT, and put around 700hp to the ground. I wanted to do a LSD swap because even with 265 R888R's out back, most of second and all of first gear were useless. I do most of my work myself when time permits, but since this involved shortening the driveshaft and changing bushings I asked Mike to take it on (he is a mechanical engineer by trade, and knows his BMWs!)
I decided to do the M3 LSD swap instead of a Wavetrac/Quaife for a few reasons:
- Way cheaper
- Reliability & tech of a M3 diff, plus added cooling with the M3 diff heatsink. The new pumpkin is a beast compared to the 335i one.
- M3 half shafts and driveshaft are way beefier than 335i. No need for DSS axles (save $1000).
- No deductibles or cores to send in when done. I can resell all my old parts!
This wouldn't have happened without the excellent threads by
Theconnman2 (
http://www.e90post.com/forums/showthread.php?t=1341843) and
GeorgeSmooth (
http://www.e90post.com/forums/showthread.php?t=321625). These guys rock, and hopefully this thread adds to their already awesome work.
I started by researching all the parts they listed, and then by buying off eBay and craigslist. I also found some parts at online scrap yards, but was able to find cheaper stuff on the other two sites. Any of them should work though, so do whatever you find easiest.
Final parts list (for me).
Your list will be different!:
- M3 half shafts from 2011 (right/left). - $359 shipped - Found some that came with the proper bolts and retainers, which saved me $150. If you're getting these pulled for your build, GET THE BOLTS. Your 335i ones WON'T FIT. These are much more beefy than 335i half shafts, so you get a free upgrade here and no need for DSS axles.
- M3 DCT driveshaft. - $200 shipped - Came with guibo and center bearing.
- M3 DCT differential from 2008. - $580 shipped - Must be DCT for 6MT cars, as it maintains a (close) to stock 3.15 ratio. Note that these may require special balancing bolts or washers, depending on the paint mark on the differential. I was lucky and mine had a white paint mark, meaning no balancing hardware was necessary.
- Hardware
- Driveshaft gasket - 26117507842 - $8.85
- Bolts - 26117526322 - $23.64
- Bolts - 26117527475 - $33.96
- Nuts - 26127536563 - $9.00
- Retainers - 33212283013 - $16.68
- New differential bushings (not necessary, but a good idea) - Rear PowerFlex PFR5-1226 - $48.99, front PowerFlex PFR5-426 - $50.99.
- Labor - $600
- Driveshaft rework - $100
So my total for parts was
$1231, labor was
$600, and driveshaft rework was
$100.
To put one of the other LSD options in comparison, we will just stick to parts/rework cost without bushings. Labor will be really variable. On N54Tuning, the Wavetrac for my car (2009) would be $2694.00. Then you send back the core, and total is $1499+$35 shipping + $85 core shipping return = $1619. So I only saved about $288 to start with, but in the process I got upgraded and beefier half shafts, an upgraded and beefier axle, and a much beefier LSD/pumpkin with heat spreader than the LSD replacements for the 335i pumpkin. Seems like a no-brainer to me.
OH, and I get to sell all my old parts and probably get a lot of money back!
So now that the costing/parts are done, here are the install pics. We will be doing a writeup soon as well, but this install is a bit more difficult due to needing bushing removal tools and a good way to remove axles (air hammer in our case).
Pics:
On the "lift" and ready for swapping.
Giant nuts on the 335i driveshaft to diff connection. These require a really big wrench. Make sure you measure your driveshaft lengths
BEFORE removing anything, as you will need those lengths to have the new driveshaft reworked.
Center support bearing unbolted
M3 diff/driveshaft on the left, 335i on the right. Notice how much bigger the M3 differential is, and how much more beefy the heatsinks are?
Here you can (kinda) see that the front half of the M3 shaft is longer than the 335i one. This is why it needs to be reworked by a professional driveshaft shop.
This is after the driveshaft was reworked. The front flange from the 335i is different than the M3, so the M3 front shaft needs to be cut down and shortened, and then have the 335i flange welded on.
Here are my lengths, but yours
will be different. Do not use these measurements before checking yours personally.
Hard to tell here, but the flanges are slightly different sizes. Need to make sure you 335i one is used for the finished driveshaft.
These are the two center support bearings. M3 on the left, 335i on right. You will need to put your 335i one on the driveshaft you are having reworked/balanced. The M3 one sits lower, so can't be used or your angles won't be right!
M3 axle (bottom) vs 335i axle (top). The M3 half shaft is MUCH beefier.
Old bushings coming out...
New (stiffer) bushings going in...
M3 diff in place. Notice the giant heatsink on this guy. Much nicer than the 335i pumpkin, which you won't get if you just do a Wavetrac/Quaife swap...
That's it! The car now gets some traction in 1st, and hooks pretty well in 2nd. Way better than it was before. Also feels substantially better in corners than it did before the swap. I know a lot of people argue that a LSD isn't needed since we have the BMW braking assist to "simulate" a LSD, but to be honest it feels totally different. Well worth the money.
Hope this thread helps!
Josh