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BMW E91 Differential and Gearing Upgrades

BMW E91 Differential and Gearing Upgrades Upgrading various parts of the differential can have tremendous benefits in your car's performance. It's easy to forget that the differential is a source for making your car faster and handle better so it's often overlooked. The engine is not the only place to make the car faster. Our differential options vary from gearing upgrades to limited slip conversions. You can purchase the ring & pinion gear sets on their own (professional installation required) or have us build a diff around your own specifcations. The options are almost endless! Every custom-built diff is fully rebuilt with seals and bearings. We also design and supply bushing options to reduce driveline wind-up, finned differential covers for better cooling, and more!

Ratio Changes - Changing the differential gearing is one of the best and most-effective upgrades you can make on any BMW (old or new). By using a shorter (numerically higher) final drive ratio you are increasing your RPM relative to road speed - this puts you in a more powerful RPM range than before! Since you're in a 'meatier' part of the power band you're now putting down more power/torque to the ground. If you can trade outright top speed for faster acceleration at daily speeds then this is the perfect upgrade for you.

Limited Slip Upgrades - Sadly, many BMWs today are not equipped with a limited slip (posi-traction) differential. BMW has tried to compensate by using traction control that cuts power at the engine or applies the brakes to retard wheel spin (or a combination of both). But nothing beats the function and feel of a a true LSD which may be why BMW continues to use them in M cars. Our LSD upgrades can be done a number of different ways - a factory-type limited slip unit with either 2 or 3 clutch packs, helical type, OS Giken unit, or something truly custom. We can also vary ramp angles and setup to change the limited-slip behavior under acceleration, deceleration, and cornering. Need a custom diff? Call or e-mail to have a quote.
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E9X 325i/328i/330i Differential Upgrade - 3.64 Original BMW

This is a complete differential to change the gearing of a manual transmission E90/E92 325i, 328i, or 330i (not for xi models) to a 3.64 ratio final drive. The standard gearing on the manual transmission cars is 3.15 or 3.23, making this E90 diff significantly shorter. This diff is from a 330i automatic where the gear ratio has to be shorter to make up for the transmission gearing differences and extra weight. This will dramatically improve acceleration on any 325i, 328i or 330i INSTANTLY! If you are looking for better off-the-line or rolling acceleration, and are willing to sacrifice a little top-speed (some of us don't get up to 150mph), this is one of the best ways to achieve it with almost no downside. There are few things that can improve your 0-to-60 and 0-to-100 times as much as shorter gearing, and this differential is clearly a best "bang-for-buck" solution for dramatically better acceleration. Since this is an Original BMW part it carries the same BMW two year warranty as any other new part. So there's no need to take a chance on a used part from a private seller. (former BMW part number 33107519944)

Changing gear ratio changes the RPM range for any given speed. Use the chart below for examples of speed vs RPM changes for the 3.64 diff.
 

2006 330i, 6-speed manual, stock 3.15 gears, 255/35-18" rear tires

Gear RatioGearSpeedRPM

40 MPH in 4th

3.154th40 MPH2,100 RPM

3.644th40 MPH2,400 RPM

70 MPH Cruise

3.156th70 MPH2,500 RPM

3.646th70 MPH2,900 RPM

5th Gear Speed @ 6,000 RPM

3.155th142 MPH6,000 RPM

3.645th123 MPH6,000 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 E90 will top out at.2006-2011 325i or 328i, 6-speed manual, stock 3.23 gears, 255/35-18" rear tires

(click to expand)

Gear RatioGearSpeedRPM

40 MPH in 4th

3.234th40 MPH2,150 RPM

3.644th40 MPH2,400 RPM

70 MPH Cruise

3.236th70 MPH2,600 RPM

3.646th70 MPH2,900 RPM

5th Gear Speed @ 6,000 RPM

3.235th138 MPH6,000 RPM

3.645th123 MPH6,000 RPM

Speed in 5th gear at 6,000 RPM is for theoretical and comparison purposes only. It doesn't mean that these speeds are actually reachable.


A $100 refundable core charge must be added at the time of order. This core charge can be refunded when you ship your original diff back to us.

This item fits the following BMWs with manual transmission only:
2006-2011 E90 BMW 325i 328i 330i - Sedan
2006-2012 E91 BMW 325i 328i - Wagon
2007-2013 E92 BMW 328i - Coupe
2007-2013 E93 BMW 328i - Convertible

Genuine BMW
Part #: 33107566176
Price: $1940.66 (USD) 
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E9X 325i/328i Differential Upgrade - Custom Options One of the best upgrades to be made is custom building a differential. There are a lot of options to make improvements to the diff including gear sizing changes, added limited slip units, and limited slip lock-up options. It's easy to overlook the differential when planning your car's upgrades but it's one of the best areas to get return from your modification spending. Using a shorter (numerically higher) gear ratio will give you better acceleration and the limited slip effect will help get that power to the pavement. Changing the limited slip lock-up will change how the car behaves in corners - low lock-up will introduce more wheel spin; a higher lock-up will give more grip to the rear wheels but may induce an understeer condition (too much power pushing the car straight); a variable lock-up will give you the optimum balance. Our experience in diff building, car prep, and racing will ensure we get you the correct custom build for your specific driving conditions.

Gearing Changes The 325i and 328 come from the factory with a 3.23 ratio. Using a shorter gear ratio (numerically higher) will give you better acceleration but will reduce your top speed. The higher ratio puts you at a higher RPM point for any given speed. This puts you further up in the power band, giving you more torque to the ground. Click the banner below to see examples.

2006-2011 325i or 328i, 6-speed manual, 255/35-18" rear tires
(click to expand)
Gear RatioGearSpeedRPM
40 MPH in 4th
3.234th40 MPH2,150 RPM
3.644th40 MPH2,400 RPM
3.914th40 MPH2,550 RPM
70 MPH Cruise
3.236th70 MPH2,600 RPM
3.646th70 MPH2,900 RPM
3.916th70 MPH3,100 RPM
5th Gear Speed @ 6,000 RPM
3.235th138 MPH6,000 RPM
3.645th123 MPH6,000 RPM
3.915th114 MPH6,000 RPM
These are just a range using three gear ratios (stock, middle, extreme). Speeds and RPM will obviously change in between ratios.
Speed in 5th gear at 6,000 RPM is for theoretical and comparison purposes only. It doesn't mean that these speeds are actually reachable.

Limited Slip Options. The non-M models of the E90 did not come with a limited slip unit. Instead, BMW used DTC (Dynamic Traction Control) to cut engine power, apply the brake(s), or a combination of both. A limited slip operates independently from either of those systems. With the LSD installed the DTC system does not engage as often. The LSD transfers torque mechanically to the opposite wheel. It will then allow some wheelspin before the traction control kicks in. If you turn off traction control you still have the torque transfer of the LSD working and then wheel spin. So you can get traction in the corner and some wheelspin out of it to facilitate rotation without engine power being cut so soon. Our limited slip units are either 2 or 3 clutch 'factory type' units with a pre-set lock-up (usually 40-60%) or the multi-disc OS Giken 0-100% variable lock-up.

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:
2006-2011 E90 E91 E92 E93 BMW 325i 328i
Turner Motorsport
Part #: TMS21526
Price: $1699.00 (USD) 
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OS Giken Limited Slip Differential Fluid - 80w-250 - 1 liter The OS Giken Super Lock LSD Gear Oil 80W-250 1 Liter FR is the OS Giken's very own special blend of gear oil which does an excellent job of lubricating and protecting your Super Lock LSD from failure. Through use of this high quality liquid, your Super Lock LSD will last much longer if regular oil changes are performed.

Type: FULL SYNTHETIC
SAE: 80W-250
API: GL-5
Flash point: 208℃
Viscosity: 320.5(40℃), 43.7(100℃)
OS Giken
Part #: OS250R
Price: $49.95 (USD) 
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ECS Magnetic Differential Oil Drain Plug You use a magnetic drain plug for your engine oil, right? Why not apply the same proactive thinking to the differential too? This is a direct replacement magnetic differential drain plug for your BMW. It will catch and retain fine and larger metal particles in your diff oil. If you're proactive in your diff oil servicing, you will catch a minor issue long before it becomes a headache. Diff drain plug includes one sealing o-ring.
ECS
Part #: 009314ECS01A
Price: $21.95 (USD) 
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Differential Drain Plug with O-Ring - Most BMWs This is the front or rear Genuine BMW differential fluid drain plug for many BMWs. This can also be the transfer case plug or automatic transmission plug on some BMWs.

+ Year & Model Applications
(click to expand)
This item fits the following BMWs:
1970-1976 2002 BMW 1600 2002 2002tii
2008+ E82 BMW 128i 135i 1M Coupe
1977-1983 E21 BMW 320i 323i
1984-1991 E30 BMW 318i 318is 318ic 325e 325es 325i 325ic 325is 325ix M3
1992-1998 E36 BMW 318i 318is 318ti 318ic 323is 323ic 325i 325is 325ic 328i 328is 328ic M3
1999-2005 E46 BMW 323i 323ci 325i 325ci 325xi 328i 328ci 330i 330ci 330xi M3
2006-2011 E90 BMW 325i 325xi 328i 328xi 328i xDrive 330i 330xi 335d 335i 335xi 335i xDrive M3 - Sedan
2006-2012 E91 BMW 325xi 328i 328xi 328i xDrive - Wagon
2007-2012 E92 BMW 328i 328xi 328i xDrive 335i 335is 335xi 335i xDrive M3 - Coupe
2007-2012 E93 BMW 328i 335i M3 - Convertible
1976-1981 E12 BMW 528i 530i
1982-1988 E28 BMW 524td 528e 533i 535i 535is M5
1989-1995 E34 BMW 525i 530i 535i 540i M5
1997-2003 E39 BMW 525i 528i 530i 540i M5
2004-2010 E60 BMW 525i 525xi 530i 530xi 528i 528xi 528i xDrive 535i 535xi 535i xDrive 545i 550i M5
2010+ F07 BMW 535i GT, 535i xDrive GT, 550i GT, 550i xDrive GT
2011+ F10 BMW 528i 528i xDrive 535i 535i xDrive 550i 550i xDrive M5
1982-1989 E24 BMW 633csi 635csi M6
2004-2010 E63 BMW 645ci 650i M6
2012+ F12 BMW 640i 650i
1981-1987 E23 BMW 733i 735i
1988-1994 E32 BMW 735i 735il 740i 740il 750il
1995-2001 E38 BMW 740i 740il 750il
2002-2008 E65 BMW 745i 745li 750i 750li 760i 760li
2009+ F01 BMW 740i 740li 750i 750li 750i xDrive 750li xDrive 760li
1990-1999 E31 BMW 840i 840ci 850i 850ci 850csi
2004-2010 E83 BMW X3 2.5i X3 3.0i X3 3.0si
2011+ F25 BMW X3 xDrive28i X3 xDrive35i
2000-2006 E53 BMW X5 3.0i X5 4.4i X5 4.6is X5 4.8is
2007-2013 E70 BMW X5 3.0si X5 4.8i X5 xDrive30i X5 xDrive35d X5 xDrive35i X5 xDrive48i X5M
2008+ E71 BMW X6 xDrive35i X6 xDrive50i X6M
1997-2002 Z3 BMW Z3 1.9 Z3 2.3 Z3 2.5i Z3 2.8 Z3 3.0i M Roadster M Coupe
2003-2008 E85 BMW Z4 2.5i Z4 3.0i Z4 3.0si Z4 M Roadster M Coupe
2009+ Z4 BMW Z4 sDrive30i Z4 sDrive35i Z4 sDrive35is
2000-2003 E52 BMW Z8 Roadster

Genuine BMW
Part #: 33117525064
Price: $6.63 (USD) 
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