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E9X M3 DCT Differential Upgrade - Custom Options

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A custom differential is one of the best upgrades to have done to your E90 or E92 M3. Not only can you get more performance but you can also address the weak points in the M Variable limited slip diff. It's easy to forget about the rear axle when you're considering performance upgrades but changing the gearing is in the top 3 things to do to make the car faster. A custom diff is also a rebuilt unit with new seals, bearings, and limited slip unit.

Gearing The E9X M3 gearing depends on which transmission/clutch spec your car has - 6MT or the DCT. The DCT comes with a taller 3.15 gear set (taller than the 3.85 used in the manual transmission cars) to make up for the different transmission ratios and the additional 7th gear. But there's always more acceleration to be had with a shorter gear set and we have quite a few to choose from for either transmission. Your speed vs RPM obviously changes with a different gear set. Use the chart below for examples of the differences.

2009 M3, 7-speed DCT, 265/35-19" rear tires

(click to expand)

Gear RatioGearSpeedRPM

4th Gear @ 40 MPH

3.154th41 MPH2,750 RPM

3.624th39 MPH3,000 RPM

70 MPH Cruise

3.157th70 MPH2,800 RPM

3.627th70 MPH3,250 RPM

6th Gear Speed at Redline

3.156th171 MPH8,250 RPM

3.626th149 MPH8,250 RPM

Why 6th? Because 7th does not have the mechanical advantage to get past wind resistance at these speeds - it is more of a cruise/overdrive gear. Using 6th for comparison purposes is much more relevant than having to take into account wind direction, resistance, grade, elevation, tire sizing, etc. These numbers are for comparisons among gear ratios only, not to determine what your M3 will top out at.
Limited Slip Options The M3's M Variable locking differential is genius when it's working properly. Unfortunately, as many M3 owners have come to find, the system only has a service life of 80,000 miles (sometimes less) and then the viscous unit inside starts to fail (is your's clunking?). We can rebuild the internals and bring it back to a perfectly-functioning viscous M Variable unit. Or you may choose to lose the variable lock in favor of a traditional clutch-type or helical diff with a set locking. We also build diffs with Quiafe, Kaaz, and OS Giken (favorite of the Turner racing team) limited slip units.

Core Charge. If we are building a diff from our own stock a refundable core charge will apply until we get your original diff back. You have a maximum of 30 days from the time you receive the diff to send it back us for a refund. Click here for more detail and explanation of the core charge.

*For full core deposit return, factory diff with 3.15 gearing must be sent in*

FAQ: For a full FAQ on the custom diff process, click here.

This item fits the following BMWs:
2008-2011 E90 BMW M3 DCT - Sedan
2008-2013 E92 BMW M3 DCT - Coupe
2008-2013 E93 BMW M3 DCT - Convertible

Loading Kit Configurator

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Kit Configurator

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Add REM bearing polish?

Add REM ring & pinion polish?

Core Charge

Select a diff ratio:

Select a limited slip type:

Base differential

This Part Fits the Following BMWs

Make Model Submodel Engine
BMW E90 M3 S65 4.0L
BMW E92 M3 S65 4.0L
BMW E93 M3 S65 4.0L
*The above product applications have been written by Turner Motorsport. All warranties, product application, fitment, and performance are the responsibility of Turner Motorsport. For additional information see the terms of use.
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