Shortly after the N54 powered 335i and 135i were released, enthusiasts and tuners
wanted to ‘fix’ the lack of limited slip differential. Making easy and abundant
power was simple with the twin turbo inline 6, but putting it to the ground was
Enter the infamous final drive. Open, LSD, welded, bolted, large body, small body,
3.08, 3.46 etc etc. We will try to make sense of everything with this blog entry.
Open vs. LSD:
The 335i and 135i were not offered with a limited slip differential. Yes,
BMW sold a twin turbo, 6MT sporty car without a LSD. No factory option, nothing.
So, owners had to rely on the aftermarket for a solution. Initially the solution
was pretty simply, till BMW switched things up on us.
LSD – limited slip differential:
Welded vs. Bolted:
Very early 6MT equipped cars had a traditional ‘bolted’ setup where the ring gear
was bolted to the gear carrier. Shortly after, the engineers in Munich decided to
weld, not bolt the ring gear to the gear carrier. Well, that complicates matters
Bolted: (we are using a bolted aftermarket diff for illustration purposes)
Master Reference Chart:
Does your car have a welded or bolted differential??
chart above. As you can see, the majority of 335i and 135i owners are blessed
with the welded differential. This makes adding a LSD a bit challenging, as the
ring gear must be separated from the carrier carefully to ensure it can be re-used.
Very few shops can do this properly and consistently, but we pioneered the best way of performing this operation which
allowed us to add a Quaife ATB etc. with no problems.
Large or small differential?
There are 2 differential (housing or ‘pumpkin’) sizes. The table above shows which cars have which size.
So, a Quaife ATB limited slip unit designed for the 6MT large housing will not work
in your 2009 335i automatic. Fortunately, we have Quaife ATB, Wavetrac and OS Giken solutions for both the
large and small differentials in stock at all times. Here are some pics so you can
see the dramatic difference:
chart above. All 6MT cars were equipped with 3.08 final drive ratios. Automatic
cars had 3.46 ratios. Note: we have built a few 3.46 differentials for 6MT cars
and the owners were thrilled. They were willing to sacrifice top speed for an incredible
power band around town
Lastly, DCT equipped cars have 2.56 and diesel cars have 2.81 final drive ratios.
When you modify your N54 or N55 powered E9X or E8X, a proper differential is an
essential modification if you want to put all of that power to the ground. While
it is quite confusing, I hope this entry makes it a bit easier to understand. We
have built 100s of differentials, so you can rely on our sales staff to answer any
other questions you may have!
Click here to see how a 335i 135i VAC Performance Built Differential
Click here to buy a 335i 135i VAC Performance Built Differential!