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    BMW E30 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.
    You're currently viewing parts for your (E30) 3-series 1984-1991. Reset your chassis
    For accurate results, specify your year and model below.
    This is the differential cover gasket / diff seal for E30 3 series, 1984-1991.
    Part #: 33111210405
    Price: $3.95 (USD) 
    Quantity:   
    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+ 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

    Part #: 33117525064
    Price: $5.95 (USD) 
    Quantity:   
    Upgrading or rebuilding the differential is one of the keys to the performance of the E30 325 or E30 M3. If you're stuck with a tall gear ratio you're going to be left behind on most acceleration runs. And if you have installed an M50/S50/S52 engine the gearing should be changed as well to make better use of the new torque curve.

    Gearing Changes 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 banners below to see how different ratios relate to particular speeds.

    Gearing Charts:
    E30 M20, Getrag 5-speed manual, 205/50-15" rear tires
    (click to expand)
    Gear Ratio Gear Speed RPM
    70 MPH Cruise
    3.73 5th 70 MPH 3,080 RPM
    3.91 5th 70 MPH 3,250 RPM
    4.10 5th 70 MPH 3,400 RPM
    Theoretical Top Speed With Raised Rev Limit
    3.73 5th 159 MPH 7,000 RPM
    3.91 5th 152 MPH 7,000 RPM
    4.10 5th 145 MPH 7,000 RPM
    These are just a range using a stock and a selection of alternative gear ratios. Speeds and RPM will obviously change in between ratios.
    Speed in 5th gear at 7000 RPM is for theoretical and comparison purposes only. It doesn't mean that these speeds are actually reachable.
    E30 M50, M3 ZF 5-speed manual, 225/50-15" rear tires
    (click to expand)
    Gear Ratio Gear Speed RPM
    70 MPH Cruise
    3.73 5th 70 MPH 3,750 RPM
    3.46 5th 70 MPH 3,400 RPM
    3.25 5th 70 MPH 3,250 RPM
    Theoretical Top Speed With Raised Rev Limit
    3.73 5th 133 MPH 7,000 RPM
    3.46 5th 144 MPH 7,000 RPM
    3.25 5th 153 MPH 7,000 RPM
    These are just a range using a stock and a selection of alternative gear ratios. Speeds and RPM will obviously change in between ratios.
    Speed in 5th gear at 7000 RPM is for theoretical and comparison purposes only. It doesn't mean that these speeds are actually reachable.

    Limited Slip Options. If you're lucky enough to have an E30 with a factory limited slip differential we don't need to make too many changes. But we will rebuild it for you. If you do not have an LSD already you will want to get one, especially with an M50 swap. Without a limited-slip you're suffering from 'One Tire Fire' - all of your power goes through one wheel. The limited slip will balance the torque through both rear wheels before the one begins to spin (depending on the lock-up you choose). We offer limited-slip options that are similar to the factory 2 or 3 disc limited slip, Quaife helical style (no clutch packs), and OS Giken multi-disc variable LSD that our race team uses.

    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. There is a $400 charge for a factory LSD diff and a $200 for a factory non-LSD (open) diff. To make the process simple, all custom diff orders are charged $400 and the refund will be based on the diff that you send back. Click here for more detail and explanation of the core charge.

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

    This custom differential fits the following BMWs:
    1984-1991 E30 BMW 318i 318is 318ic 325e 325es 325i 325ic 325is M3
    Part #: E30-DIFFERENTIAL
    Price: $1,424.00 (USD) 
    This factory finned differential cover bolts directly to the E30 diff housing. This is a must for track cars with limited slip differentials. The clutch packs in these diffs generate a lot of heat, the more heat you can dissipate the better. The fins on this cover will do just that. This is an inexpensive upgrade that may save you a lot of money down the road. Plus it looks cool.

    Kit includes cover, gasket and all necessary hardware. :
  • 1 x 33112228335 - Differential Cover
  • 1 x 33111210405 - Differential Gasket
  • 2 x 07119914114 - Bolt
  • 4 x 07119921522 - Bolt
  • 2 x 07119921541 - Bolt


    This item fits the following BMWs:
    1984-1991 E30 BMW 325e 325es 325i 325ic 325is M3
  • Part #: 33112228335KIT
    Price: $350.50 (USD) 
    Quantity:   
    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℃)
    Part #: OS250R
    Price: $49.95 (USD) 
    Quantity:   
    This is a solid rubber Original BMW differential mount. It's solid so that the differential won't move around too much under load. Ideal for use on either a street driven car or for use on a race track.

    This item fits the following BMWs:
    1984-1991 E30 BMW 325e 325es 325i 325ic 325is 325ix M3
    Part #: 33171134802
    Price: $103.95 (USD) 
    Quantity:   
    Made in the USAThis rear differential mount is made from near-solid Delrin plastic and is a direct replacement upgrade from the stock rubber piece. The Delrin material has almost no flex to it, which results in better response, more feedback, and more power transferred to the wheels. Because the diff on these cars acts as a 'stressed' part of the rear suspension, we only advise using this solid mount with our Turner Solid Aluminum Subframe Mounts. This part is legal in many racing classes.

    This item fits the following BMWs:
    1984-1991 E30 BMW 318i 318is 318ic 325e 325es 325i 325ic 325is 325ix M3
    Part #: TDR3080007
    Price: $46.95 (USD) 
    Quantity:   
    This Genuine BMW speedometer / pulse generator is mounted in the back of the differential and provides wheel speed information to the instrument cluster speedometer.

    This item fits the following BMWs:
    1988-1991 E30 BMW 318i 318is 318ic 325e 325es 325i 325ic 325is M3
    7/1987-1989 E24 BMW 635csi M6
    1997 Z3 BMW Z3 2.8
    1998-2002 Z3 BMW M Roadster M Coupe
    Part #: 62168355008
    Price: $33.95 (USD) 
    Quantity:   
    This Genuine BMW speedometer / pulse generator is mounted in the back of the differential and provides wheel speed information to the instrument cluster speedometer.

    This item fits the following BMWs:
    1984-1987 E30 BMW 318i 325e 325es 325i 325ic 325is
    1982-1988 E28 BMW 524td 528e 533i 535i 535is M5
    1983-6/1987 E24 BMW 633csi 635csi M6
    1981-1987 E23 BMW 733i 735i
    Part #: 62161369906
    Price: $76.95 (USD) 
    Quantity: