BMW Differential and Gearing Upgrades

Harness unused potential. Drive with confidence. Engineered to maximize strength and cooling performance while utilizing the unused secondary factory differential mount for enhanced support and driveline stability.

Our Turner Motorsport Dual-Mount Differential Cover is purpose-built to reinforce one of the most critical components in the G8X M3/M4 drivetrain. From the factory, BMW includes a secondary bushing location in the rear subframe but leaves it unused. Our solution fully capitalizes on this overlooked feature, giving the differential a second point of support for improved rigidity, reduced movement, and enhanced driveline response under load.

This cover is more than just a mounting upgrade. It’s precision-machined from 6061-T6 billet aluminum for exceptional strength without unnecessary weight. An aggressive fin profile improves thermal efficiency, helping to lower fluid temperatures in high-stress environments. Inside, the cover features an embossed channel that mirrors the ring gear path, ensuring fluid stays in contact where it's needed most, improving cooling and lubrication in all conditions.

Whether you're carving corners on the street or pushing the limits on track, this differential cover is designed to keep your rear end cool, stable, and responsive.

Key Features and Benefits:

The dual-mount design utilizes the factory-provided secondary bushing location, adding critical support to reduce differential deflection, extend bushing life, and minimize wheel hop.
CNC-machined from 6061-T6 billet aluminum, offering high strength and a precise fit.
Built-in cooling fins increase surface area for improved heat dissipation and lower differential fluid temperatures.
Internally contoured to follow the ring gear profile, promoting consistent fluid coverage and effective lubrication.
Maintains a 1.1-liter fluid capacity, closely matching OEM specifications for ease of servicing.
Integrated -6 AN ports support the addition of an external differential cooler for increased fluid volume and extended service intervals.
Compatible with the factory differential fluid temperature sensor and includes provisions for 1/4” NPT aftermarket sensors.
Product Development:

Like all Turner Motorsport performance solutions, this differential cover was developed in-house by our dedicated Research and Development team. Designed, engineered, tested, and quality-inspected using advanced tools including FARO laser scanning for reverse engineering, SolidWorks 3D CAD modeling, in-house rapid prototyping, and extensive long-term testing, you can trust that this part meets the highest standards of fit, function, and durability.

From spirited street driving to full-throttle track days, the Turner Motorsport Dual-Mount Differential Cover ensures your G8X delivers the response, strength, and cooling capacity it needs when it matters most.

Single piece 6061 construction, optimized cooling, provisions for temp sensor, and external cooler with removable air duct.

Built to last, made from a single piece of 6061 billet aluminum with a rugged and good-looking hard-coat anodizing our diff cover can handle anything you throw at it. Not only is it an absolute masterpiece to look at but the billet diff cover checks all the boxes for features needed. Reinforced mounting ears for strength and stability, never again will you break an ear off your diff cover like the factory units are known to do. Each ear is not only unified with the one-piece billet cover but also feature added material for the highest durability possible. This diff cover is cool, literally, the entire construction was designed with optimized cooling in mind. External fins are strategically placed on the rear face, bottom, and between the mounting ears of the cover, serving as effective heat sinks for optimal heat dissipation. This ensures stable temperatures, promoting longevity for both the fluid and your differential. Additionally, the internal design ensures continuous oiling and lubrication to the ring gear, maintaining its stability and preventing fatigue by controlling heat more effectively. An internal baffle at the cover's corner helps maintain proper pressure and prevents cavitation.

All of the OEM features were retained along with the upgrades. The mounting surface was designed to be compatible with both the OEM gasket or RTV of your choosing, some people don't trust the gaskets and we get it. You can transfer your speed sensor directly to your upgraded billet cover and it even features a provision for the sensor wire mounting. Factory bushing geometry allows you to use any E36 diff busing including rubber, poly, and even solid mounts. The drain and fill plugs on the diff cover are upgraded to -6AN using the provided high-pressure fittings with replaceable o-rings. The drain and fill plugs can now also be used for expanding to an external oil cooler allowing you to further expand the fluid capacity for optimized cooling and service intervals. To keep an eye on things from the driver seat is 1/8 NPT provision for temp sensors, this product from Turner has you covered at every turn.

Why the upgrade?

If you're new to differential covers used in earlier generations like the E30, you'll find significant improvements in the OEM E36 cover. Unlike the E30's single mount design, the E36 features a dual mount design, which was introduced to address common issues such as broken mounts due to worn-out bushings and aggressive driving. This upgrade significantly enhanced durability and reliability.

While the factory E36 differential cover was a significant improvement with its dual mounts compared to the previous generation, there are still some shortcomings that the original cover doesn't address. Most factory differential covers, including those on the E36, are cast from aluminum. However, due to the porous nature of cast aluminum, the mounting ears on these covers cannot withstand the intense shocks typical in motorsport or in vehicles with significantly increased power.

Upgrading to our Reinforced Billet Differential cover gives you the strength you need to push your car to its limits without worrying about snapping a diff mount from clutch kicking or other shocks to the drivetrain. In addition to its enhanced strength, this differential cover includes numerous other upgrades and conveniences. These include improved cooling and lubrication for the ring gear, upgraded fill and drain plugs, and the option to expand an external oil cooler for extreme motorsport usage. Designed to complement both upgraded daily drivers and extensively modified track cars, it also boasts a visually appealing design.

Key Benefits:

Reinforced mounting ears for strength and stability - never again will you break an ear off during an aggressive drive or track event
External fins on the back side, bottom, and mounting ears on the casing for maximum cooling and consistent fluid temps
Removeable air duct to direct air across the cooling fins for even more temperature control
Optimized internal design to keep fluid consistently on the ring gear
Integrated breather to prevent cavitation by venting the appropriate amount of pressure being built up in the diff housing
-6AN ports to incorporate the use of a differential cooler - this increases capacity and lowers temps allowing for extended fluid change intervals
1/8 NPT fitting for the use of a temp sensor to monitor fluid temperature
Design:

Single piece 6061 Billet aluminum construction
T6 Black hard coat anodizing for superior corrosion resistance and aesthetics
Compatible with most differential coolers(-6AN) and temp sensors(1/8 NPT)
Designed to accommodate oversized rear sway bars
Retains OEM mounting features including the use of the OEM gasket
Factory geometry bushing size for use with OEM and aftermarket poly bushings
Removeable air duct for easy access to sensors and drain/fill plug
Retains OEM speed sensor and wire mount location
Product development:

Our Reinforced Billet Diff Cover was designed, engineered, tested, and quality inspected by our Research and Development team at Turner. Nothing but the highest level of precision and quality through leading-edge product development technology including FARO laser scanning for reverse engineering and quality inspection, SolidWorks 3D CAD modeling, rapid prototyping utilizing our in-house 3D printer, and rigorous long-term product testing.

Modern BMW's are beginning to leave the performance derived handling and power delivery in the past as the demand for more comfort and features rises. The stiff suspension components designed around having the best driving experience from a luxury car has been left for the M models and replaced with soft rubber bushings and mounts. Unfortunately, this is a good move by BMW to support the masses.

The obvious approach was to offer products so the modern BMW can be upgraded into the car the enthusiast desires, superb handling, control, and a direct delivery of power to the rear wheels. When you upgrade to our Delrin subframe mounts you reconnect that power with almost zero negative feedback.

The added appeal to someone looking to take one of these machines on the race track is Delrin can be used when solid mounts are needed and aluminum is not an option with strict regulations found in??Grand-Am, BMW CCA, and other racing series.

Product features:

• Precision machined Delrin(TM) 150 bushings.
• Precision machined 6061-T6 aluminum inserts.?
• Class legal for any racing class that does not allow a solid subframe bushing.?

Performance Benefits:

• Eliminates subframe movement for more direct throttle and suspension? response.?
• Minimizes wheel hop due to subframe deflection and movement.?

?

***Installation Instructions***

These GAC differential bushings/mounts fit the following BMWs:?
2014+?F22 BMW?228i 228iX M235i M235iX?
2012+?F30 BMW?320i 320iX 328i 328iX 335i 335iX - Sedan?
2014+?F34 BMW?328i 328iX 335iX - Gran Turismo?
2014+?F32 BMW?428i 428iX 435i 435iX - Coupe?
2014+?F33 BMW?428i 428iX 435i 435iX - Convertible

2014+?F36?BMW?428iX -Gran Coupe?

Single piece 6061 construction, optimized cooling, provisions for temp sensor, and external cooler with removable air duct.

Built to last, made from a single piece of 6061 billet aluminum with a rugged and good-looking hard-coat anodizing the Turner diff cover can handle anything you throw at it. Not only is it an absolute masterpiece, but this billet diff cover checks all the boxes for features needed. Reinforced mounting ear for strength and stability. The mounting ear is unified with the one-piece billet cover and features added material for the highest durability possible. This diff cover is cool, literally, the entire construction was designed with optimized cooling in mind. External fins are strategically placed on the rear face, bottom, and between the mounting ears of the cover, serving as effective heat sinks for optimal heat dissipation. This ensures stable temperatures, promoting longevity for both the fluid and your differential. Additionally, the internal design ensures continuous oiling and lubrication of the ring gear, maintaining its stability and preventing fatigue by controlling heat more effectively. An internal baffle at the cover's corner helps maintain proper pressure and prevents cavitation.

All of the OEM features were retained along with the upgrades. The drain and fill plugs on the diff cover are upgraded to -6AN using the provided high-pressure fittings with replaceable o-rings. The drain and fill plugs can now be used for an external oil cooler allowing you to further expand the fluid capacity for optimized cooling and service intervals. To keep an eye on things from the driver seat is 1/8 NPT provision for temp sensors, this product from Turner has you covered at every turn.

Upgrading to our Turner Billet Differential cover gives you the strength you need to push your car to its limits without worrying about snapping a diff mount from clutch kicking or other shocks to the drivetrain. In addition to its enhanced strength, this differential cover includes numerous other upgrades and conveniences. These include improved cooling and lubrication for the ring gear, upgraded fill and drain plugs, and the option to expand an external oil cooler for extreme motorsport usage. Designed to complement both upgraded daily drivers and extensively modified track cars, it also offers a visually appealing design.

Key Benefits:

Reinforced mounting ear for strength and stability
16% Increased fluid capacity
External fins on the back side, bottom, and mounting ear on the casing for maximum cooling and consistent fluid temps
Removeable air duct to direct air across the cooling fins for even more temperature control
Optimized internal design to keep fluid consistently on the ring gear
Integrated breather to prevent cavitation by venting the appropriate amount of pressure being built up in the diff housing
-6AN ports to incorporate the use of a differential cooler - this increases capacity and lowers temps allowing for extended fluid change intervals
1/8 NPT fitting for the use of a temp sensor to monitor fluid temperature
Design:

Fits manual transmission Large Case 215mm differentials
Single piece 6061 Billet aluminum construction
T6 Black hard coat anodizing for superior corrosion resistance and aesthetics
Compatible with most differential coolers(-6AN) and temp sensors(1/8 NPT)
Designed to accommodate oversized rear sway bars
Retains OEM mounting features
Factory geometry bushing size for use with OEM and aftermarket poly bushings
Removeable air duct for easy access to sensors and drain/fill plug

The Powerflex Rear Diff Mount Bushing for the BMW E21 offers a robust solution to support and stabilize the differential, replacing the standard rubber bushings with durable polyurethane. This upgrade minimizes unwanted differential movement, enhancing driving dynamics and responsiveness.

Key Benefits:

1. Enhanced Stability: By minimizing differential movement, Powerflex bushings ensure consistent alignment, giving better rear-end stability.
2. Improved Longevity: Unlike rubber, polyurethane is resistant to aging and degradation from elements like oil and road debris.
3. Responsive Handling: With reduced play in the differential mount, power transfer becomes more direct, allowing for sharper throttle response.
4. Vibration Dampening Options: Powerflex offers options like the Black Series for motorsport applications and the standard Purple for everyday performance with minimal increase in vibration.

These bushings are popular among E21 owners who want a durable, performance-oriented solution that balances comfort and handling precision. Ideal for both spirited driving and daily use.

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.