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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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Elring - Corporate Logo
T#:54852011
Part#: B16.900
In Stock
New Item
$ 33.99 USD
Free Shipping on orders $49 and up
This high-grade Elring replacement gasket set is engineered for drivers who demand factory-level reliability and zero-compromise sealing performance.
Powerflex - Corporate Logo
T#:54281644
Part#: PFR5-325H
Back Ordered
New Item
$ 44.99 USD
$ 44.99 USD
The Powerflex Heritage Series is a premium motorsport upgrade engineered to eliminate critical differential deflection. Molded from an advanced, proprietary polyurethane formula, this bushing stabilizes the differential nose under high-torque loading.
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Powerflex - Corporate Logo
T#:54352781
Part#: PFR5-1625H
Ships in 1 Business Day
New Item
$ 89.99 USD
$ 89.99 USD

Powerflex - Corporate Logo
T#:54281641
Part#: PFR5-326H
Ships in 1 Business Day
New Item
$ 139.99 USD
$ 139.99 USD
The Powerflex Heritage Collection replaces the soft factory unit with an engineered, high-performance polyurethane compound. It is designed to constrain differential rotation and stabilize the driveline without changing the classic aesthetic of the vehicle undercarriage.
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Powerflex - Corporate Logo
T#:54317182
Part#: PFR5-324H
Ships in 1 Business Day
New Item
$ 51.99 USD
$ 51.99 USD
Ensure your build operates at peak mechanical efficiency. Eliminate driveline slop and secure your differential assembly with track-proven engineering.

Powerflex - Corporate Logo
T#:54352762
Part#: PFR5-2025H
Ships in 1 Business Day
New Item
$ 89.99 USD
$ 89.99 USD
By stabilizing the differential's position relative to the subframe, the rear diff bushing helps maintain static axle angles under extreme loads, reducing wear on peripheral drivetrain components and providing a highly predictable, repeatable platform for track setups.
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Elring - Corporate Logo
T#:53008820
Part#: 33108860348
Ships in 2 Business Days
New Item
$ 44.99

This product was last offered at the strikethrough price on
05-08-2026

$ 43.99 USD
$ 43.99 USD
The Axle Shaft Seal is a critical component designed to prevent fluid leaks around the axle shaft, ensuring the proper function of the vehicle’s drivetrain system. This seal helps maintain the integrity of the differential, preventing dirt, water, or contaminants from entering the diff while keeping lubricants contained.
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Genuine BMW - Corporate Logo
T#:338092
Part#: 33107566176
Ships in 7 Business Days
Starting at $ 2,412.29 USD
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Starting at $ 2,412.29 USD
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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

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Genuine BMW - Corporate Logo
T#:56869544
Part#: 31507648879
Ships in 8 Business Days
New Item
4% off MSRP $ 3,279.99

MSRP stands for Manufacturer's Suggested Retail Price. This is the suggested retail price provided by the manufacturer, supplier or seller.

$ 3,132.99 USD
4% off MSRP
$ 3,279.99

MSRP stands for Manufacturer's Suggested Retail Price. This is the suggested retail price provided by the manufacturer, supplier or seller.

$ 3,132.99 USD
Elring - Corporate Logo
T#:54852004
Part#: B46.610
Special Order: No Guaranteed ETA
New Item
$ 14.99 USD
Free Shipping on orders $49 and up
This OEM-quality replacement shaft seal from Elring is the perfect fix for keeping your gear oil where it belongs.
Enthusiast Bundles - Corporate Logo
T#:37419758
Part#: 049424LAEBKT
Ships in 1 day
Sale - Save 17% $ 1,381.99

This product was last offered at the strikethrough price on
05-05-2026

$ 1,149.99 USD
Free Shipping on orders $49 and up
Sale - Save 17%
$ 1,381.99

This product was last offered at the strikethrough price on
05-05-2026

$ 1,149.99 USD
Free Shipping on orders $49 and up

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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Powerflex - Corporate Logo
T#:54352763
Part#: PFR5-2025BLK
Back Ordered
New Item
$ 102.99 USD
$ 102.99 USD
The Powerflex Black Series is engineered for maximum performance and minimum deflection