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E60 M5, E63 M6 Differential Upgrade - Custom Options

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A custom differential is one of the best upgrades to have done to your E60 M5 and M6. 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 E60 M5 diff comes with a relatively short 3.62 gear ratio. They could use a shorter gear because the engine redline is so high - the car has a long power band and the gear spacing allows you to stay well within that range. There's always more acceleration to be had with a shorter gear set. BMW Motorsport supplies 3.91 or 4.10 options and there are other gear ratios to select in our custom builds. We sell a lot of 3.91 gear sets for the M5 because it works seamlessly with the SMG transmission. Other ratios may have issues with shifting, especially in full auto mode. Your speed vs RPM obviously changes with a different gear set. Use the chart below for examples of the differences.

2008 E60 M5, 7-speed SMG, 285/35-19" rear tires
(click to expand)
Gear RatioGearSpeedRPM
40 MPH In 4th
3.624th40 MPH2,500 RPM
3.914th40 MPH2,750 RPM
4.104th40 MPH2,800 RPM
70 MPH Cruise
3.627th70 MPH2,600 RPM
3.917th70 MPH2,875 RPM
4.107th70 MPH3,000 RPM
6th Gear Speed at Redline
3.626th182 MPH8,250 RPM
3.916th169 MPH8,250 RPM
4.106th161 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 M5/M6 will top out at.

Limited Slip Options The M5's M Variable locking differential is genius when it's working properly. Unfortunately, as many M3/M5/M6 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.

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

This item fits the following BMWs:
2006-2010 E60 BMW M5
2006-2010 E63 E64 BMW M6

Loading Kit Configurator

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Kit Configurator

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Select a gear ratio:

Select a limited slip type:

Add REM ring & pinion polish?

Core Charge

Add REM bearing polish?

E60 M5/E63 M6 Custom Differential:

This Part Fits the Following BMWs

Make Model Submodel Engine
BMW E60 M5 S85 5.0L
BMW E63 M6 S85 5.0L
BMW E64 M6 S85 5.0L
*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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