BMW Differential and Gearing Upgrades

This kit includes Turner Motorsport solid aluminum differential race mounts pre installed in the differential cover for a quick install. These mounts where developed by Turner Motorsport for their Grand-Am Cup E46 M3 race cars, the advantages of solid aluminum mounts is increased suspension & drivetrain response, less drivetrain loss resulting in more wheel horsepower, and longevity - they effectively last forever. These CNC-machined mounts are a direct replacement for the stock rubber pieces, and have been lightened to remove excess weight. 

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

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.