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      07-18-2012, 12:36 PM   #1
Brian_VACsales's Avatar

Drives: E92 M3 VF Supercharged, 135i
Join Date: Feb 2011
Location: Philadelphia, PA

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Post VAC Motorsports | 335i Billet Finned Differential Cover

Buy now:

We build a lot of differentials. When we took possession of our 135i in 2008 we quickly realized that the stock cover did not have a drain. Since the goal was to add a performance limited slip unit, we felt it made sense to make a new differential cover which would really work for street and track use. We put a lot of time into the design, focusing on both absolute function and form. A LOT of machine work goes into this piece, I will let the pics speak for themselves.

BMW will tell you that the gear oil is a life-time fill. We disagree. Since This frustration is compounded by the fact that the OE diff cover doesn't even have drain and fill plugs!

Under hard use, LSDs equipped diffs can run very hot, even the OS Giken diffs have been known to cook gear oil. Our finned cover is stronger and offers much better heat dissipation that these cars need when going to the track.


-Increase oil capacity - by a whopping 50%

-Increase cooling capacity - via heat-dissipating fins

-Machined from a single billet of 6061-T6 aluminum - for unmatched strength, elimination of flex and durability. Cast covers can and do fail.

-Drain and fill provisions - stock units does not have a drain so oil changes are quite difficult

-“AN” style plugs - -8AN o-ring fittings. For the serious road race enthusiast, this cover allows you to simply 'plug in' an external differential oil-cooler

-Integral and baffled vent for street cars - All differentials must have a vent

-Pre-machined catch-can provision -simply 'plug in' an external catch can fitting (for racecars)

-Pre-machined provision for differential oil temperature sensor - just plug your temp sensor in, no drama

-OE Quality 10.9 grade flanged hex head hardware provided

-No adverse effects on ride quality or noise

-Excellent ground clearance

-Available in street length (11") and race length (12") (see pics below)

-Fits RWD and AWD models

-[b]Convertible Models (E93 and E88 cabrio) - these may fit with custom clearance work, but we do not recommend these covers.

-As always, Made in the USA in house at VAC

Baffled vent:

Brian Casella
Sales Representative, VAC Motorsports
Office: 215.462.4666 | Fax: 215.462.4667 EXT 13 | Email:

Last edited by Brian_VACsales; 11-22-2013 at 12:11 PM.