Rogue Engineering Performance Differentials

A look at the parts replaced in a Rogue Engineering E46 M3 Performance Differential.
How many parts does your builder replace?

Racecar speed secrets for the Street!

What's the Secret?

One of the benefits of being associated with professional race teams is being privy to their "speed secrets" that they use on the track.  One of these secrets include the allowable rear differential gear changes.

For the Grand-Am GS E46 M3s, they were allowed to change their gearing from stock 3.62 to 3.91.  Of course, most "street" guys know that the 4.10 ratio is really the most desirable gear (but again, not allowed in Grand-Am racing rules).  After many seasons of racing, we were told that these race-prepped vehicles had their rear differentials torn down to be rebuilt for the upcoming season.  What they found out inside the differential, told an interesting story.

Start From Scratch

One of the mandatory keys to the rebuilds is replacing EVERYTHING in the differential possible.  Although the M-Variable unit is left intact, every single bolt, seal, bearing, o-ring, crush washer and circlip are replaced.  Even though the existing one may have been ok, it's not worth a potential failure for a small part.  Typical racecar mentality is to replace everything with new parts.  However, most all differential "builders" will not spend the extra $500+ in parts (shown above, not including the BMW Motorsport ring/pinion) when building a differential.  Most will replace the absolute necessary parts (like a bearing or a crush washer).  The other problem is that the above parts are not available "easily" from the local BMW dealer as the E46 M3 differential is not available as individual parts.  The BMW Motorsport gearset is the most costly item, at close to $900 from BMW Motorsport approved dealers.  These are usually only available as special order through Germany.

More Preparation

One of the other obsessive details is the REM polishing of the BMW Motorsport ring and pinion parts.  By having this additional finishing process done, it lowers the frictional resistance between the teeth and lowers differential temperatures, if only a little.  After a full season of racing, REM polished gears show virtually NO wear and can be used again!  Gearsets that do not have this finishing process done do show additional wear after a full season of use.  This kind of service typically adds approximately $195 to the gearset.  All our differentials get this finishing.

REM Polished 4.10 Ring and Pinion

Break-In?  Drive it!

Using factory fluid, the there is no "wrong way" to drive the newly installed differential.  These differentials are built by the same company building for Pro Grand-Am teams and expect the differentials to be used hard and put away wet.  Their only requirement is to drain and refill using factory BMW differential fluid after 1200 miles.  That's it.

For The Select Few

We have a few number of E46 M3 differential cores available, but at most times, these are supplied on a wait-list basis and require a $1000 deposit.  4.10s are the common differentials we have built.  3.91s gears are special order, and require a $1000 deposit.

Currently, the differentials are priced at $2550 plus core, plus shipping.  They are shipped WITHOUT the factory rear cover, as yours will be reused.

To reserve a differential, contact us at info@rogueengineering.com.