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.

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

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

Differential bushings are responsible for keeping the differential in solid alignment while dampening drivetrain vibration. While OE rubber bushings are fine when they are new from the factory, aged and worn out rubber bushings create a multitude of issues that can range from annoying to dangerous. As a factory bushing ages, it begins to harden and become brittle. When this happens the bushing will actually shrink and allow for movement at the differential mounting point. At this point, the differential is free to shift under load causing a noticeable clunking noise under acceleration and deceleration and massively increasing the stress on the driveshaft and axles. Manual transmissions suffer the worst from this as it can make shifting difficult since the differential will shift when the clutch is engaged and disengaged.

By replacing these bushings with full polyurethane, the movement is eliminated since the mounting point is supported by a much stiffer material that will not harden or shrink over time. This means less stress on the driveshaft and axles and greater longevity of supporting components. 

Powerflex Black Series bushings are the ultimate in track and race bushings. Featuring 95A durometer polyurethane, Black Series bushings are 25% stiffer than street bushings. Engineered to perform, Powerflex performance polyurethane control arm bushings offer a supreme level of control, while still providing enough comfort for the street, with advanced polyurethane that reduces NVH that often accompanies lesser bushings. Expect improved acceleration response, more direct shifting feel and overall improved drivetrain composure with Powerflex performance polyurethane bushings.

Poweflex is a leading manufacturer of aftermarket suspension bushings. Using state of the art design and manufacturing, all replacement bushings are engineered to out-perform and out-last the ones that came in the car. Each line of bushings is meticulously tested and then re-tested to ensure perfect fitment and enduring quality through the life of the vehicle. A full lifetime warranty backs every one of their products and demonstrates the level of confidence and commitment Powerflex has to their customers. 

Differential bushings are responsible for keeping the differential in solid alignment while dampening drivetrain vibration. While OE rubber bushings are fine when they are new from the factory, aged and worn out rubber bushings create a multitude of issues that can range from annoying to dangerous. As a factory bushing ages, it begins to harden and become brittle. When this happens the bushing will actually shrink and allow for movement at the differential mounting point. At this point, the differential is free to shift under load causing a noticeable clunking noise under acceleration and deceleration and massively increasing the stress on the driveshaft and axles. Manual transmissions suffer the worst from this as it can make shifting difficult since the differential will shift when the clutch is engaged and disengaged.

By replacing these bushings with full polyurethane, the movement is eliminated since the mounting point is supported by a much stiffer material that will not harden or shrink over time. This means less stress on the driveshaft and axles and greater longevity of supporting components. 

Engineered to perform, Powerflex performance polyurethane differential bushings offer a supreme level of control, while still providing enough comfort for the street, with advanced polyurethane that reduces NVH that often accompanies lesser bushings. Expect improved acceleration response, more direct shifting feel and overall improved drivetrain composure with Powerflex performance polyurethane bushings.

Poweflex is a leading manufacturer of aftermarket suspension bushings. Using state of the art design and manufacturing, all replacement bushings are engineered to out-perform and out-last the ones that came in the car. Each line of bushings is meticulously tested and then re-tested to ensure perfect fitment and enduring quality through the life of the vehicle. A full lifetime warranty backs every one of their products and demonstrates the level of confidence and commitment Powerflex has to their customers. 

Differential bushings are responsible for keeping the differential in solid alignment while dampening drivetrain vibration. While OE rubber bushings are fine when they are new from the factory, aged and worn out rubber bushings create a multitude of issues that can range from annoying to dangerous. As a factory bushing ages, it begins to harden and become brittle. When this happens the bushing will actually shrink and allow for movement at the differential mounting point. At this point, the differential is free to shift under load causing a noticeable clunking noise under acceleration and deceleration and massively increasing the stress on the driveshaft and axles. Manual transmissions suffer the worst from this as it can make shifting difficult since the differential will shift when the clutch is engaged and disengaged.

By replacing these bushings with full polyurethane, the movement is eliminated since the mounting point is supported by a much stiffer material that will not harden or shrink over time. This means less stress on the driveshaft and axles and greater longevity of supporting components. 

Engineered to perform, Powerflex performance polyurethane differential bushings offer a supreme level of control, while still providing enough comfort for the street, with advanced polyurethane that reduces NVH that often accompanies lesser bushings. Expect improved acceleration response, more direct shifting feel and overall improved drivetrain composure with Powerflex performance polyurethane bushings.

Poweflex is a leading manufacturer of aftermarket suspension bushings. Using state of the art design and manufacturing, all replacement bushings are engineered to out-perform and out-last the ones that came in the car. Each line of bushings is meticulously tested and then re-tested to ensure perfect fitment and enduring quality through the life of the vehicle. A full lifetime warranty backs every one of their products and demonstrates the level of confidence and commitment Powerflex has to their customers. 

The Powerflex Rear Differential Rear Mount Bushings for the BMW E39 5 Series are designed to provide a significant upgrade to the vehicle's rear differential system by replacing the stock rubber bushings with high-performance polyurethane. This enhancement leads to improved handling, stability, and durability.

Key Benefits:

1. Enhanced Differential Control: The stiffer polyurethane material reduces unwanted movement and flex in the differential mount, ensuring better alignment and stability under load. This translates to improved power delivery and handling during cornering and acceleration.

2. Increased Longevity: These bushings are crafted to resist wear and degradation from oil, heat, and road debris, offering superior durability compared to traditional rubber bushings. This longevity ensures that the performance benefits are maintained over time.

3. Improved Driver Feedback: By minimizing movement in the rear differential, these bushings enhance the connection between the vehicle and the driver. This results in better feedback and control, allowing for a more engaging driving experience.

4. Direct Fit for Easy Installation: Designed specifically for the E39 5 Series, these bushings fit directly into the existing differential mounts, facilitating a hassle-free installation process without the need for modifications.

This upgrade is perfect for BMW E39 5 Series enthusiasts who want to improve their vehicle's handling and performance, making it suitable for both daily driving and spirited performance applications. The Powerflex Rear Differential Rear Mount Bushings provide a reliable solution to enhance the overall effectiveness of the rear suspension system.

Differential bushings are responsible for keeping the differential in solid alignment while dampening drivetrain vibration. While OE rubber bushings are fine when they are new from the factory, aged and worn out rubber bushings create a multitude of issues that can range from annoying to dangerous. As a factory bushing ages, it begins to harden and become brittle. When this happens the bushing will actually shrink and allow for movement at the differential mounting point. At this point, the differential is free to shift under load causing a noticeable clunking noise under acceleration and deceleration and massively increasing the stress on the driveshaft and axles. Manual transmissions suffer the worst from this as it can make shifting difficult since the differential will shift when the clutch is engaged and disengaged.

By replacing these bushings with full polyurethane, the movement is eliminated since the mounting point is supported by a much stiffer material that will not harden or shrink over time. This means less stress on the driveshaft and axles and greater longevity of supporting components. 

Powerflex Black Series bushings are the ultimate in track and race bushings. Featuring 95A durometer polyurethane, Black Series bushings are 25% stiffer than street bushings. Engineered to perform, Powerflex performance polyurethane control arm bushings offer a supreme level of control, while still providing enough comfort for the street, with advanced polyurethane that reduces NVH that often accompanies lesser bushings. Expect improved acceleration response, more direct shifting feel and overall improved drivetrain composure with Powerflex performance polyurethane bushings.

Poweflex is a leading manufacturer of aftermarket suspension bushings. Using state of the art design and manufacturing, all replacement bushings are engineered to out-perform and out-last the ones that came in the car. Each line of bushings is meticulously tested and then re-tested to ensure perfect fitment and enduring quality through the life of the vehicle. A full lifetime warranty backs every one of their products and demonstrates the level of confidence and commitment Powerflex has to their customers.