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BMW 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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Turner Motorsport - Corporate Logo
T#:593924
Part#: 027030TMS01
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When both extreme-duty protection and saving every gram matters: the Turner Magnetic Differential 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. Direct replacement for Genuine BMW part number(s): 33117525064, 33110308370, 33110152626
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ECS - Corporate Logo
T#:30662812
Part#: 055059LA01
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As your E30 ages, the rear differential bushing can crack, dry rot, and split. It's time for an upgrade. The ECS Tuning Heavy Duty Differential Bushing is crafted with performance in mind. Instead of using polyurethane, which is known for increasing NVH, the enthusiasts at ECS chose HD 70D rubber. This material offers a close-to-factory feel without the excess deflection of softer bushings, ensuring a pleasurable driving experience free from differential whine and excess movement.

Features & Benefits:

Eliminates Weak OEM Mount: The aging E30 chassis deserves an upgrade. Replace your old, cracked, and worn factory bushing with this HD alternative for improved performance. Perfect for Street or Track: Constructed from HD rubber instead of polyurethane or Delrin, this bushing provides comfort for daily driving while remaining effective in performance applications. Added Responsiveness: The 70D HD rubber compound is stiffer than the stock material, reducing drivetrain movement and effectively locking down your rear differential. Easy Installation: Precision-manufactured to the exact specifications of your OEM differential bushing, the ECS heavy-duty replacement installs just like the factory component. Whether you are replacing an aging factory bushing, removing excess driveline movement, or balancing performance and comfort, ECS Tuning has you covered with their Heavy Duty Rear Differential Bushing.

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ECS - Corporate Logo
T#:35121162
Part#: 056350LA01
Ships on Oct 5, 2026
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Convert your open differential to a locked differential without the costly expense of an LSD replacement.

Get your car ready for aggressive track driving or drifting without purchasing or replacing your differential. The weld-in plates strengthen your diff and allow both wheels to engage simultaneously giving you a more predictable and capable track car.

An open differential allows the wheels to spin at different speeds and sends power to the wheel with the least amount of traction. This may be a good feature for your regular everyday driver but limits you on the track. The weld-in plates simulate a driving experience similar to a limited-slip differential allowing you to put power to both wheels in a low traction area or initiate drifts.

Features and benefits:

Added strength to your differential gears
Converts from open differential
Fabricated to fit in the spider gears for an easier weld and increased confidence
Made from 7 gauge mild steel, formed to fit

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ECS - Corporate Logo
T#:583896
Part#: 000920ECS01
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Ensure the longevity of your BMW's drivetrain with ECS Tuning's Magnetic Plugs. These plugs are meticulously engineered in-house to provide a perfect fit and feature a permanent magnet attached to the plug body. The magnet effectively attracts and captures tiny abrasive and ferrous metal particles, preventing their circulation through lubrication systems. Metal particles can accumulate due to various conditions such as normal wear, machining operations, casting flaws, and stress usage, leading to excessive wear of vital components. ECS Tuning's Magnetic Plugs help alleviate this concern by trapping these particles, thus safeguarding the internal components of your drivetrain. With a convenient 17mm hex head design, these plugs eliminate the need for special tools required for OEM plugs.

Key Benefits:

  • Removes abrasive metal particles from drivetrain fluid
  • Prevents excessive wear to internal components
  • Meticulously engineered for a perfect fit
  • Features a permanent magnet for efficient particle capture
  • Convenient 17mm hex head design for easy installation
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ECS - Corporate Logo
T#:363117
Part#: 002447ECS03
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BMW E46 Z4 Rear Polyurethane Differential Bushing Performance is the ultimate upgrade for enhancing the connection between your BMW's chassis and differential. Designed by Turner Motorsport, this performance bushing replaces the soft factory rubber with durable polyurethane, offering superior control and response. By minimizing vibrations and reducing deflection, this bushing ensures a more direct and responsive driving experience, making it a must-have for any performance-oriented BMW E46 or Z4 owner.

  • Enhanced Performance: Replaces the soft factory rubber with durable polyurethane for improved driveline response.
  • Reduced Vibrations: Minimizes vibrations between the chassis and differential, providing a more connected driving experience.
  • Increased Durability: Made from high-quality polyurethane, offering long-lasting performance under demanding conditions.
  • Improved Control: Reduces deflection, ensuring a more precise and responsive handling experience.
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Packaged by Turner - Corporate Logo
T#:42133544
Part#: 835225790TKT
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The kit includes 2 Quarts of Red line 75w90 - 57904 and brand new Rein rear diff oil drain plug M22x1.5
Packaged by Turner - Corporate Logo
T#:15710761
Part#: 33117525064-KT
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Often overlooked, scheduled rear differential service is very important. Over time gear lube breaks down causing bearings and internal components fail. Regular maintenance will keep your vehicle running properly for years to come. Kit includes 3 Bottles of Castrol SAF-XJ 75w140 2 Drain plugs
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T#:24344778
Part#: ECSTMSPDBKT
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Turner recommends running drivetrain mounts of all the same variety - if you are using poly engine mounts, you should also use poly transmission mounts. This kit is your solution to make sure all components of your vehicle are working with each other to achieve the performance you're looking for. Polyurethane material is more resistant to water, ozone, and chemicals, maintaining its resiliency and elasticity longer than conventional rubber. Keep your vehicle planted for spirited driving while having crisper throttle response and reduce drivetrain movement along with wheel hop. Kit includes: Turner Engine Mount Set - 60A Polyurethane ECS Transmission Mount Set - Street 70A Polyurethane ECS Differential Bushing Set - 95A Polyurethane ECS Subframe Mount Set - 95A - Polyurethane
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T#:56327180
Part#: F3XAWDFDKT5
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This kit combines Red Line 75W85 GL-5 Synthetic Gear Oil with Rein OEM replacement plugs in order to perform a full drain and fill service on both of your differentials
Packaged by Turner - Corporate Logo
T#:15744025
Part#: 331175250640-KT
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Often overlooked, scheduled rear differential service is very important. Over time gear lube breaks down causing bearings and internal components fail. Regular maintenance will keep your vehicle running properly for years to come. Three bottle of Genuine BMW Limited Slip Gear Lube 1 New Genuine BMW Drain/Fill plugs 1 ECS Magnetic Differential Oil Drain Plug Drain plug O-ring
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Packaged by Turner - Corporate Logo
T#:56327200
Part#: F3XAWDFDKT6
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This kit combines Motul 75W85 GL-5 Synthetic Gear Oil with Rein OEM replacement plugs in order to perform a full drain and fill service on both of your differentials


Packaged by Turner - Corporate Logo
T#:42099854
Part#: 07512293972T3KT
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Maintain smooth power distribution, protect your drivetrain, and extend the life of your BMW xDrive system with the Complete Xdrive Differential And Transfer Case Service Kit - E90, E91, E92, E60, E61, E70.
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Enthusiast Bundles - Corporate Logo
T#:37419758
Part#: 049424LAEBKT
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E36 188mm Reinforced Billet Aluminum Differential Cover

Engineered from high-quality 6061 billet aluminum, this differential cover is built for resilience and designed for performance. Hard-coat anodized for a sleek finish and superior corrosion resistance, it not only looks great but also brings functional improvements in strength and cooling. Turner Motorsport has added reinforced mounting ears to withstand the toughest driving conditions—preventing the breakages common with OEM covers.

This cover doesn’t just endure—it performs. The cover features strategically placed external fins on the rear face, base, and mounting ears to efficiently dissipate heat, keeping temperatures stable for optimal fluid longevity and differential health. Inside, the design promotes consistent oiling of the ring gear, reducing wear by ensuring critical cooling and lubrication. An integrated baffle keeps pressure stable and minimizes cavitation.

Compatibility is at the core of the design: it’s compatible with OEM gaskets or RTV, and it retains the factory bushing geometry for easy integration with rubber, poly, and even solid mounts. The upgraded -6AN drain and fill plugs allow expansion for an external oil cooler, ideal for high-performance applications. Plus, a 1/8 NPT port allows for real-time monitoring of differential fluid temperatures.

Key Benefits:

Reinforced mounting ears for robust support—no more broken ears during aggressive driving or track days Optimized cooling with fins on rear face, base, and mounting ears Removable air duct to direct airflow across fins for maximum temperature control Improved internal design to maintain consistent lubrication on the ring gear -6AN ports for external cooler compatibility, increasing fluid capacity and extending change intervals 1/8 NPT port for temperature sensor integration to monitor fluid heat Design Highlights:

Precision-milled from 6061 billet aluminum with a T6 hard-coat anodized finish Fits E36 medium case 188mm differentials Compatible with differential coolers (-6AN) and temperature sensors (1/8 NPT) Works with OEM speed sensor, OEM gasket, and oversized sway bars Designed for easy maintenance with a removable air duct and accessible drain/fill plug ECS Tuning E36 Polyurethane Transmission Mount Set – Street

The ECS Polyurethane Transmission Mounts in this kit provide a solid connection between transmission and chassis, enhancing stability and reducing unwanted drivetrain movement. Built for durability, these mounts feature polyurethane with a 70A durometer for a perfect balance of comfort and performance. Compared to OEM rubber mounts, polyurethane provides less deflection, better power transfer, and much longer life under stress.

Polyurethane’s natural resistance to water, oil, and wear ensures these mounts maintain shape and performance even under heavy compression, making them ideal for spirited driving and track use. The mounts include a mechanical interlock for secure, reliable performance—even under high-torque, forced-induction scenarios. For those seeking a more aggressive setup, ECS also offers an 80A durometer Race mount.

Key Features:

Reduces transmission movement, minimizing mis-shifts and over-revs High-quality polyurethane bonded to 304 Stainless Steel Engaging driving experience with enhanced feedback and control Available in Street (70A) and Race (80A) applications for tailored performance Enjoy smoother shifts, firmer power delivery, and a more engaging drive with the ECS Polyurethane Transmission Mounts.

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