350+hp E30 M3 with S54 and 6MT Swap – The White Elephant

This is one of those cars that every single person on earth loves – seriously. This is not a show car. It is a close to 300k mile chassis built to be driven and driven hard -which just happens to be in nearly perfect condition :)  Yani had us build this beast to withstand the levels of abuse he is famous for dishing out.  If you see the Elephant on the skidpad, road course etc. rest assured that Yani is pushing it past 10/10ths – just the way we like our cars to be driven


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Ring and Pinion – What is REM Treatment?

REM treatment is a proprietary process which eliminates the imperfections left over by the machining process. In very simplified terms, the “peaks” left on metal parts by various manufacturing processes are removed using vibratory equipment in conjunction with patented solutions to speed up the process.

Although the result of the REM(tm) process is a beautiful finish, it is Important to realize that the system does not polish the part. The process involves two steps. The first, referred to as the refinement process involves a chemical interaction on the surface of the part. A soft, thin (one micron) film is formed on the surface of the part. The part interacts with the ceramic media in a special vibratory tub, this film is physically removed from the “peaks” of the processed part and the “valleys” are unaffected. The chemically induced film re-forms only at the peaks that are interacting with the vibratory media, and the process repeats itself. Over time, the peaks are removed, leaving only the valleys, producing the improved micro finish. The second step is referred to as the burnish process. After the required micro finish is achieved, a mild alkaline mixture is introduced. After a relatively short period a polished, chrome-like finish is produced. In addition to the polishing effects, this step effectively removes all traces of the film formation from the refinement process.

The result is a much more uniform surface that provides many impressive benefits for motorsports, including:
-Reduced Friction
-Lower Operating Temperatures
-Extended Component Life
-Reduced Noise
-Increased Efficiency
-More Power To The Ground

Pictured:  E46 M3 Performance Built Differential with optional REM Treatment

credits:  http://www.taylor-race.com/isotropic.cfm, http://www.remchem.com/

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335i and 135i Differential FAQ (No LSD, really?)

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 not.

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 a bit!

Bolted: (we are using a bolted aftermarket diff for illustration purposes)


Master Reference Chart:

Does your car have a welded or bolted differential??
See 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:

Gear Ratios:
See 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 is made!

Click here to buy a 335i 135i VAC Performance Built Differential!

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VAC Motorsports – 335i, 135i Performance Built Differential – How we do it!

Hey guys,

I am proud to say that we in fact do everything in house…nothing is outsourced.

Well, this is a quick tutorial.  As everyone knows, the ring gear is welded to the carrier.  We wanted to do the best job possible, so we configured our CNC lathes and mills to handle this challenging task.  The end result is beautiful =)

VAC Performance Built Differentials are built to last with the highest quality components, procedures, and technical expertise in the industry.  We have been building BMW differentials since the 1980s – 2002, E46, E92, street, race – we have done it.

How is a VAC Performance Built Differential made? (this is not a complete list, but most major operations are covered)

1.  Photograph and inspect every differential for damage/missing parts etc.

2.  Drain and inspect fluid looking for shavings or anything odd with the fluid.

3.  Remove cover, inspect ring gear, confirm gear ratio.  Pictured:  The infamous welded ring gear.  Note how it is actually welded to the carrier.

4.  Test backlash before dissassembly.

5.  Remove axle shafts, old side cover seals, snap rings.

6.  Carefully remove the carrier.

7.  Remove inner races from carrier.

8.  Clean up the carrier, and prep for CNC operation.

9.  Set up the carrier in our ultra rigid and precise CNC lathe.  Pictured:  Stock welded ring gear/carrier on one of our lathes.

10. Machine away weld that secures the ring gear to the carrier.   This is an extremely robust weld.

11. Remove the resultant step (weld) so it is flat enough to machine.  Pictured: stock ring gear separated from carrier.

12. Machine the ring gear flat (to ensure a precise mating surface for the new unit)  Pictured:  Separated ring gear | fully machined ring gear | drilled/tapped ring gear

13. Set up the newly finished ring gear on our CNC mill.  Pictured:  Machined ring gear on our HAAS 5 axis machine.

14. Machine the ring gear to make it compatible with the limited slip unit.

Pictured:  Completed ring gear still in the HAAS mill.


After:   Note how we machine the entire face, not just the area where the LSD bolts.  Our machining method ensures ideal accuracy and reliability.  Not sure that anyone takes it this far.

15. Assemble the limited slip unit.

16. Pressure wash and paint the housing.

17. Soda blast and clean the differential.

18. Install bearings/snap rings.

19. Check pattern, install seals, gasket material and differential cover.  Pictured:  Checking the pattern on the newly assembled differential.

20. Tag and prepare for install/shipment.  Pictured:  VAC Performance Build Differential with optional Billet Differential Cover.

Buy Now! 


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BMW 1M Akrapovic Evolution Titanium Exhaust Install

A few days ago we had the pleasure of installing another Akrapovic Evolution system. This time it was on a beautiful Alpine White BMW 1M. In addition to the full exhaust system, he opted for the Akrapovic downpipe set and the wireless remote valve kit.  This slick kit allows you to open/close the valve by simply pressing an illuminated in-cabin switch.  When the valve is closed, the exhaust note is aggressive but TÜV friendly.  When open, it roars/burbles like a race car.

If you are looking for the absolute best and lightest system for the BMW 1M, look no further. I will let the photos speak for themselves.

Buy Now – Akrapovic BMW 1M Evolution Exhaust System


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