BMW Differential and Gearing Upgrades for BMW 3 Series E46 (1999-2005)

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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.

ECS Magnetic Differential Oil Drain Plug
ECS - Corporate Logo
T#:366828
Part#: 009314ECS01A
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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 Magnetic Transmission Drain/Fill Plug - E28 E39 E46 Z3
ECS - Corporate Logo
T#:392674
Part#: 012301127FMAG
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The benefit of having a magnetic drain plug is over time with use, all metallic particles floating in the gear lube from wear will be captured at the drain. This will greatly reduce any possible damage and clogging from normal transmission wear. With the drain plug holding on to those particles you're able to clean the plug at each service to ensure there isn't constant build up within the transmission or differential.

ECS Screw Plug - M24X1,5
This item fits the following BMW Chassis:
E30 M3,E39 M5,E46 M3,E30,E34,E36,E39,E46,E85 Z4

Differential Drain Plug with O-Ring - Most BMWs
Genuine BMW - Corporate Logo
T#:7923
Part#: 33117525064
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$6.98
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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 Differential Plug Gasket, 22x27 - 07119963355
Genuine BMW - Corporate Logo
T#:348476
Part#: 07119963355
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$1.00
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When servicing the rear axle and differential, it is always best to replace this sealing washer to prevent any potential leaks from forming.

Differential Input Shaft Seal - E82 E46 E9X E39 E60 Z4
Genuine BMW - Corporate Logo
T#:7924
Part#: 33121213949
In Stock
34% off MSRP $57.36
$37.89
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Replace your leaking differential input seal with this Genuine BMW part. Whenever service is performed on the differential it is a good idea to check / replace any seals. This seal measures 50mm X 80mm X 9mm. We also recommend you replace the securing plate # 33121205138 at the same time.

This item fits the following BMWs:
2011 E82 BMW 1M Coupe
2001-2006 E46 BMW M3
2008-2011 E90 BMW M3 - Sedan
2008-2013 E92 BMW M3 - Coupe
2008-2013 E93 BMW M3 - Convertible
1988 E28 BMW M5
1991-1995 E34 BMW 540i M5
1999-2003 E39 BMW M5
2006-2010 E60 BMW i M5
2011+ F10 BMW M5
1987-1989 E24 BMW M6
2006-2010 E63 BMW M6
2012+ F12 BMW M6
2013+ F06 BMW M6 Gran Coupe
1988-1994 E32 BMW 740i 740il 750il
1990-1999 E31 BMW 840i 840ci 850i 850ci 850csi
2006-2008 E85 BMW Z4 M Roadster M Coupe
E46, Z4 High Performance Finned Differential Cover
Genuine BMW - Corporate Logo
T#:1095
Part#: 33117512980
In Stock
26% off MSRP $194.15
$142.79
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This aluminum diff cover is off the Z4 Roadster and features fins on the underside for improved cooling. This is an absolute must for any E46 that sees track time, especially with an LSD installed. This is a direct bolt-on with the existing bolts and all drain and fill plugs transfer over as well. BMW recommends sealing the cover to the diff with black RTV silicone (no gasket).

This item fits the following BMWs:
1999-2006 E46 BMW 323i 323ci 325i 325ci 325xi 328i 328ci 330i 330ci 330xi (upgrade!)
2003-2008 E85 BMW Z4 2.5i Z4 3.0i Z4 3.0si (replacement)

Ring & Pinion Gear Set (R&P only) - 4.10 - E46 M3, E60 M5
Genuine BMW Motorsport - Corporate Logo
T#:21503
Part#: TMS21503
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If there was a Top 5 list of things to do on the E46 M3, a shorter gears would be in the top two... The gearing used to be overlooked when planning modifications but the 3.91 and 4.10 gears are now one of our biggest selling upgrades for the E46 M3! With a rear end gear upgrade you get the effects of adding horsepower but without adding any more stress to the engine or drivetrain. The R&P acts as a torque multiplier, getting you into the power band sooner in each gear. It's one of the best areas to get return from your modification spending. The shorter (numerically higher) rear end gears will give you better acceleration in all gears at any speed with few downsides. Want to make your car faster off the line or out of corners? Or avoid a downshift to pass on the highway? This is what you need. This 4.10 is the latest version from BMW Motorsport - shot peened and hardend for increased strength. The R&P can be installed on its own but for cars that have more than 60,000 miles it would be a better idea to rebuild the whole diff. The factory viscous limited slip units have a typical lifespan of 50-70,000 miles. We offer diff rebuilding with 4.10 or other gear options and you get a fully-rebuilt and serviced limited slip unit at the same time. Click here for our diff rebuild options.

4.10 Gearing Example: 2004 M3, 6-speed manual, 275/35-19" rear tires

Gear RatioGearSpeedRPM

40 MPH in 4th
3.62 4th 40mph 2,250rpm
4.10 4th 40mph 2,550rpm

70 MPH Cruise
3.62 6th 70mph 2,650rpm
4.10 6th 70mph 3,000rpm

5th Gear Speed at Redline
3.62 5th 175mph 8,000rpm
4.10 5th 154mph 8,000rpm

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 M3 will top out at.


This item is the genuine BMW part and the ring & pinion set only. You will need to have this professionally installed into your existing differential. BMW does not supply differential rebuild parts (bearings, shims, plates, etc.) so only a qualified shop that is experienced in BMW diff rebuilding should perform this installation. We also offer built differentials and exchanges, click here.

This item fits the following BMWs:
2001-2006 E46 BMW M3
2004-2010 E60 BMW M5 (manual transmission only)

OEM part number 33108321899

OS Giken Limited Slip Differential Fluid - 80w-250 - 1 liter
OS Giken - Corporate Logo
T#:1840
Part#: OS250R
In Stock
$49.95
$49.95
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℃)

E46 M3 Stock Differential Cover With Bushings
Genuine BMW - Corporate Logo
T#:1333
Part#: 33112282482
In Stock
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BMW does not sell the differential mounts separate from the cover. And as with all rubber mounts, they will have to be replaced at some point, forcing you to also buy a new diff cover. This is an Original BMW part.
**Note** - a paper gasket is not sold with this cover. BMW no longer uses paper gaskets - they advise the use of a silicone sealant such as RTV black.

Applications:
2001-2006 E46 M3, M3 CSL, coupe and convertible


E46 Finned Differential Cover Upgrade Kit
Packaged by Turner - Corporate Logo
T#:401688
Part#: 33117512980KT
In Stock
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The perfect upgrade for any E46, this finned differential cover increases cooling to the rear differential to prevent over heating and possible damage. This is a complete kit including fluid and drain plugs.

Includes the following

  • Aluminum finned differential cover
  • Drain & fill plug with sealing o-ring
  • 2 Quarts of Redline 75w90
Output Shaft Seal E36 M3, E39, E46
Rein - Corporate Logo
T#:2756
Part#: 23111224799
In Stock
$14.95
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Output Shaft Seal E36 M3, E39, E46 - does not fit E46 M3. this is the seal that is on the output side of the transmission.

This item fits the following BMWs:
1992-1998 E36 BMW 328i 328is 328ic M3
1999-03/2003 E46 BMW 328i 328ci 330i 330ci
1997-2003 E39 BMW 525i 528i 530i
1997-2002 Z3 BMW Z3 2.8 Z3 3.0i M Roadster M Coupe
E46 M3, E9X M3, E34 M5, E39 M5, Z4 M OS Giken Super Lock Limited Slip Differential Unit
OS Giken - Corporate Logo
T#:1387
Part#: BM237-HA
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$1,950.00
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The M Dynamic limited slip unit on the M3 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 M3 lsd 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 M3 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:
2001-2006 E46 M3 coupe & convertible
2008-2013 E9X M3 coupe & convertible
1991-1995 E34 M5 sedan
1999-2003 E39 M5 sedan
2006-2008 E85 Z4M Z4 M Coupe, Z4 M Roadster


E46, Z4 Differential Upgrade - Custom Options
Turner Motorsport - Corporate Logo
T#:340178
Part#: TMS340178
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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 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. Refer to the chart below for examples.

2002 330i, 5-speed manual, 245/40-17" rear tires

(click to expand)

Gear RatioGearSpeedRPM

40 MPH in 4th

2.934th40 MPH2,000 RPM

3.464th40 MPH2,300 RPM

3.914th40 MPH2,600 RPM

70 MPH Cruise

2.935th70 MPH2,800 RPM

3.465th70 MPH3,300 RPM

3.915th71 MPH3,750 RPM

5th Gear Speed @ 6,000 RPM

2.935th151 MPH6,000 RPM

3.465th128 MPH6,000 RPM

3.915th113 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.

2005 330i ZHP, 6-speed manual, 255/35-18" rear tires

(click to expand)

Gear RatioGearSpeedRPM

40 MPH in 4th

3.074th40 MPH2,050 RPM

3.464th40 MPH2,300 RPM

3.914th40 MPH2,550 RPM

70 MPH Cruise

3.076th70 MPH2,450 RPM

3.466th70 MPH2,750 RPM

3.916th70 MPH3,150 RPM

5th Gear Speed @ 6,000 RPM

3.075th146 MPH6,000 RPM

3.465th129 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 E46, and Z4 did not come with a limited slip unit. Instead, BMW used either the ASC (Accelerated Slip Control) or 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 ASC/DTC systems do 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 by ASC. 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:
1999-2005 E46 BMW 323i 323ci 325i 325ci 325xi 328i 328ci 330i 330ci 330xii
2003-2008 E85 BMW Z4 2.5i Z4 3.0i Z4 3.0si

E46/Spec E46 3.46 Differential Upgrade
Turner Motorsport - Corporate Logo
T#:340448
Part#: TMS221921
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The differential is one of the key components of any race car build. For the Spec E46 racing class the rules call for "3.46 gear ratio, factory housing, flanges, and mounting points. The internal parts of the differential are otherwise unrestricted, including the use of limited slip units." (as of September 2015). If you're not running one of these SE46 diffs you can expect to be passed by someone who is. The non-M E46 did not come with a limited slip so the benefits of using one are obvious - put down as much power as early as possible in the corner and gain more top speed on the straights. Don't sit and wait for your car to hook up in the corner while someone else has already gone by!

Our ideal SpecE46 diff is built with these options: 3-disc limited slip with 30/90 ramp angles, polished gears and polished carrier bearings, and the race carrier (see below). This setup has been tested and developed extensively on E46 330 and E46 M3 racecars. The 30deg angle on acceleration will engage the clutch discs sooner than a factory or "standard" LSD and give you outstanding traction accelerating out of corners. The 90deg decel will not engage the clutches so the inside drive wheel will not be pushing the car straight while you are executing braking and turn-in. This diff also works great for other E46 track cars (not just SE46). We can also build the diff in a different way if you prefer more or less clutch discs or a different style of limited slip.

A full race limited slip carrier option uses 6 clutch discs and coil springs for a completely tunable race diff. The coil springs inside the carrier control preload of the discs ensuring the limited slip is working consistently even as the discs wear. The spring tension and ramp angles can be customized for your preferences although there is a "hot setup" for SE46 cars already. The race carrier is also much lighter than the standard LSD units.

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:
2001-2006 E46 BMW 330i 330ci
E46 M3 Differential Upgrade - Custom Options
Turner Motorsport - Corporate Logo
T#:340182
Part#: TMS2052
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Starting at $2,249.00
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A custom differential is one of the best upgrades to have done to your E46 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 E46 M3 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. Your speed vs RPM obviously changes with a different gear set. Use the chart below for examples of the differences.

Gearing Charts:
2004 M3, 6-speed manual, 275/35-19" rear tires
(click to expand)
Gear RatioGearSpeedRPM
40 MPH in 4th
3.624th40 MPH2,250 RPM
3.914th40 MPH2,450 RPM
4.104th40 MPH2,550 RPM
70 MPH Cruise
3.626th70 MPH2,650 RPM
3.916th70 MPH2,900 RPM
4.106th70 MPH3,000 RPM
5th Gear Speed at Redline
3.625th175 MPH8,000 RPM
3.915th162 MPH8,000 RPM
4.105th154 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 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 th