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Limited Slip Differentials

BMW stopped using truly limited-slip differentials with the advent of the E9X and E60 platforms. The advantages between an open and limited-slip differential are seconds on the track and a massive increase in corner exit grip. Tuner motorsports offer many different types of LSDs' to suit your driving style and budget.
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E85/E86 Z4 M Differential Upgrade - Custom Options
Diffs by Turner - Corporate Logo
T#:340225
Part#: TMS21531
In Stock
Sale - Save 7% $2,249.00
Starting at $2,099.00
Free Shipping
Sale - Save 7% $2,249.00
Starting at $2,099.00
Free Shipping
A custom differential is one of the best upgrades to have done to your Z4 M. 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 MZ4 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. But 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. Your speed vs RPM obviously changes with a different gear set. Use the chart below for examples of the differences.


Example: 2008 Z4 M, 6-speed manual, 255/40-18" rear tires
(click to expand)
Gear RatioGearSpeedRPM
40 MPH in 4th
3.624th39 MPH2,250 RPM
3.914th40 MPH2,500 RPM
4.104th40 MPH2,625 RPM
70 MPH Cruise
3.626th69 MPH2,750 RPM
3.916th70 MPH3,000 RPM
4.106th70 MPH3,150 RPM
5th Gear Speed at Redline
3.625th171 MPH8,000 RPM
3.915th158 MPH8,000 RPM
4.105th151 MPH8,000 RPM
Why 5th? Because 6th does not have the mechanical advantage to get past wind resistance at these speeds - it is more of a cruise/overdrive gear. Using 5th 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 M Coupe will top out at.

Limited Slip Options The M Variable locking differential is genius when it's working properly. Unfortunately, as many M3/M5/M6/Z4M 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:
2006-2008 E85 E86 BMW Z4 M Roadster M Coupe
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Genuine BMW M Performance BMW M Performance Limited-Slip Differential - F22 228i M235i F23 M235i
Genuine BMW M Performance - Corporate Logo
T#:222981
Part#: 33108659987
In Stock
11% off MSRP $2,630.00
$2,339.52
11% off MSRP $2,630.00
$2,339.52
For the ultimate in track day performance, the M Performance Limited Slip Differential is here! The clutch-type mechanical differential features a 30% lockup on acceleration and 9% lockup on deceleration. The differential works with the existing DSC system to provide excellent traction wet or dry. It uses the stock 3.08 final drive ratio that the stock M235i uses, so fuel economy will not be affected.  This item fits the following BMWs:
2014+  F22 BMW  228i M235i
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Turner Performance Differential - E60 525/528/530
Diffs by Turner - Corporate Logo
T#:391179
Part#: E606CYLDIFFKT
In Stock
Sale - Save 15% $4,718.00
$3,999.95
Sale - Save 15% $4,718.00
$3,999.95
This is a completely rebuilt and upgraded replacement for your factory differential. The rebuild starts with replacing all seals and bearings, then adding a Helical lsd unit and freshly REM polished ring and pinon. *Differentials ship without fluid and without a cover* *Cost includes $400 core charge*
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E60 M5, E63 M6 Differential Upgrade - Custom Options
Diffs by Turner - Corporate Logo
T#:338777
Part#: TMS21533
Direct Ship, Expected Ship Date: May 27, 2021
Starting at $1,999.00
Free Shipping
Starting at $1,999.00
Free Shipping
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
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OS Giken Super Lock Limited Slip Differential Unit for E60 M5, E63 M6
OS Giken - Corporate Logo
T#:179750
Part#: BM237-HC
Direct Ship, Expected Ship Date: May 19, 2021
$2,650.00
Free Shipping
The limited slip unit on the 2006+ M5 and M6 is designed to be a pure street car differential. It's simply not up to the rigors of professional or amateur racing. The OS Giken Super Lock LSD is giant step up in from a stock viscous limited-slip unit. It's ready for the extreme conditions of racing, offers 100% progressive locking capability, and is able to do this while operating smoothly and quietly. It's use of advanced technologies that make it perfect for both street cars AND pro race cars... and everything in between. We're excited to be carrying the OS Giken LSD unit in our performance catalog, as we've been using them in our own Championship winning race cars.

OS Giken incorporated revolutionary new ideas when developing the their own limited slip diff, utilizing their accumulated racing knowledge and experience and over 4 years of development. Their design uses an unprecedented number of friction plates (up to 28 total!) for better locking force, better engagement/disengagement, and less generated heat. The end result of their efforts is the OS Giken's OS Super Lock LSD which offers incredible durability and reliability on street and track driven BMWs. The use of highest quality materials, precise machining, forged gears and sound engineering makes this LSD durable and reliable enough for road racing performance (which we can personally vouch for!). This is such a great design, in that it can be used in any situation -- whether it's for a street car, or a 100% Professional race car. Zero break-in required. Super smooth and quiet engagement, and 100% progressive locking capability. Professional installation is recommended.

This Limited Slip Differential Unit fits the following BMWs:
2006-2010 E60 M5 sedan <