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
In Stock
$25.95
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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.
E46 M3 Outer CV Boot Housing Rebuild Kit
Turner Motorsport - Corporate Logo
T#:1966
Part#: TDR4628CVJ
Ships on Jul 23, 2019
$193.95
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Made in the USA Over the years driving and racing the E46 M3 in Grand-Am racing, club racing, driving school events, and street driving, we have found that the half-shafts need to be rebuilt or replaced often. This is especially true of the outer CV joint (closest to the wheel bearing) due to the high loads on the half shafts and elevated temperature in that region. Thanks to our extensive experience in Grand-Am endurance racing, we have designed a kit to prolong CV joint life and save frequent and costly replacing of half shafts, on both street and track/race cars. The problem with rebuilding E46 half-shafts is that the CV joint ("Constant Velocity Joint") closest to the wheel bearing is not serviceable because a stamped steel housing must be cut off to access the CV joint. The housing cannot be reused, therefore necessitating replacement of the whole half-shaft. We have designed a reusable aluminum housing to make servicing the CV joint possible.

This is a custom Turner Motorsport item, originally designed for our championship-winning Grand-Am M3s. It can also be used in non-racing applications, for both track and street E46 M3s. If you are performing any work on the rear driveline of your E46 M3 (such as wheel bearings, differential work, bushings, rear sway bar / swaybar, etc) or are prepping for the race season, then now is an excellent time to perform this job as well.

Kit includes 2 CNC aluminum housings (left and right are the same) with Black anodized coating, 12 set-screws (6 per housing), 2 Viton O-rings, 8 Oetiker clamps, and 4 stainless steel breather tubes (only required for race use).

Click for instructions click for intructions (PDF)
OS Giken Limited Slip Differential Fluid - 80w-250 - 1 liter
OS Giken - Corporate Logo
T#:1840
Part#: OS250R
In Stock
$50.00
$50.00
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: 208a,,f
Viscosity: 320.5i1/4^40a,,fi1/4%0, 43.7i1/4^100a,,fi1/4%0

E46 M3 Stock Differential Cover With Bushings
Genuine BMW - Corporate Logo
T#:1333
Part#: 33112282482
In Stock
19% off MSRP $225.44
$181.95
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19% off MSRP $225.44
$181.95
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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


BMW Motorsport Ring & Pinion Gear Set (R&P only) - 3.85 - E46 M3, E60 M5, E63 M6
Genuine BMW Motorsport - Corporate Logo
T#:402875
Part#: 33108311351
In Stock
$998.95
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Hands down - one of the best performance upgrades you can make to an E46 M3, E60 M5 or E63/E64 M6! With almost no downside you can make your BMW much quicker by swapping in a new ring & pinion gear set. The gearing used to be overlooked when planning modifications but the 3.85, 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. 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. The R&P acts as a torque multiplier, putting the engine into the power band sooner for each gear. There is an 6% increase in torque at the wheels with the shorter R&P. 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.

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 3.85 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.

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

Gear RatioGearSpeedRPM

40 MPH in 4th
3.62 4th 40mph 2,250rpm
3.85 4th 40mph 2,350rpm

70 MPH Cruise
3.62 6th 70mph 2,650rpm
3.85 6th 70mph 2,800rpm

5th Gear Speed at Redline
3.62 5th 175mph 8,000rpm
3.85 5th 165mph 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
2004-2011 E63 BMW M6

OEM part number 33108311351

Differential Input Shaft Seal - E82 E46 E9X E39 E60 Z4
Genuine BMW - Corporate Logo
T#:7924
Part#: 33121213949
In Stock
35% off MSRP $57.38
$37.19
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35% off MSRP $57.38
$37.19
Free Shipping on orders $99 and up
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 $194.13
$142.79
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26% off MSRP $194.13
$142.79
Free Shipping on orders $99 and up
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
In Stock
5% off MSRP $946.61
$899.28
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5% off MSRP $946.61
$899.28
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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


Dimple Magnetic Differential Drain Plug - Multiple BMWs
Dimple - Corporate Logo
T#:581413
Part#: SSM22X1.5
In Stock
New Item
$34.95
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Gear oil works best when it is uncontaminated. Continuous friction in your differential creates tiny metal particles that contaminate the oil. These particles are measured in microns (one millionth of a meter: 25 microns = .001"). Even after an oil change, there are still contaminants left in the differential. Over time, these metal particles are circulated millions of times, polishing (wearing) down the metal components inside your differential, shortening the differential's life until it wears out. Magnetic drain plugs remove the metal particles, extending your differential's useful life. It is also less likely that you will experience oil oxidation, as the metal particles that contribute to the process of oxidation adhere to the magnet.&Newline; &Newline; We think Dimplea,,C/ makes the finest magnetic drain plugs we've ever used. What makes Dimplea,,C/ plugs different from other magnetic drain plugs? The magnets. All magnets are not created equal -- Dimple's "Black Holea,,C/" high-temperature magnets are the strongest, high-temperature, neodymium magnets in the world. Regular magnets lose magnetism at 175Adeg F; Dimple's neodymium magnets are rated at over 300Adeg F, so they continue to grab those destructive metal particles even when things get hot. In addition, Dimple's magnets degrade at the incredibly slow rate of A1/2 of 1% every 100 years, so they are guaranteed to work throughout your lifetime. &Newline; &Newline; Custom made for BMW vehicles, featuring a large 8 mm neodymium magnet rated at 300Adeg F.&Newline; &Newline; M22 x 1.5&Newline; &Newline; Replaces Genuine BMW Part # 33117525064

E46, Z4 Differential Upgrade - Custom Options
Turner Motorsport - Corporate Logo
T#:340178
Part#: TMS340178
Direct Ship
Starting at $1,830.95
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Starting at $1,830.95
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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 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
Direct Ship
$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