BMW Differential and Gearing Upgrades

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.

Enhance rear-end control and put more power to the ground with a straightforward 3-piece design that installs with ease. The factory rubber may favor ride comfort, but it struggles to keep up when driving gets aggressive. As it wears, the OEM bushing can soften and deform, reducing stability and allowing wheel hop to creep in when you need traction most.

Our 95A durometer polyurethane bushings solve that problem. Engineered to strike the perfect balance between soft factory rubber and harsh solid mounts, they significantly reduce differential movement without introducing excessive vibration. The result is more efficient power transfer, so your torque goes straight to the rear wheels instead of being lost in drivetrain flex.

Features & Benefits:

Minimizes differential movement and instability to help eliminate wheel hop
Two-piece 95A split polyurethane design for easier installation
Precision-fit insert reinforces the bushing and strengthens mounting points
Resistant to road salt, oils, and harsh chemicals
Compatible with dual mount differential plates
Design:

Type II Anodized 6061-T6 CNC billet aluminum inserts for superior corrosion resistance and durability.
95A Polyurethane 2-Piece Isolator.
Product Development:

Our Rear Differential Bushings are designed, engineered, tested, and quality inspected by our Research & Development team. Our development process includes leading-edge product technology: 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

Bushings tends to wear over time and split or even break free from the internal sleeve, causing excessive movement and sloppy control feel. Genuine BMW bushings are the perfect option to restore suspension back to day 1 quality.

As a leading source of high performance BMW parts and accessories since 1993, we at Turner Motorsport are honored to be the go-to supplier for tens of thousands of enthusiasts the world over. With over two decades of parts, service, and racing experience under our belt, we provide only quality performance and replacement parts.  All of our performance parts are those we would (and do!) install and run on our own cars, as well as replacement parts that are Genuine BMW or from OEM manufacturers. We only offer parts we know you can trust to perform!

Genuine BMW Rubber Mounting Rear -
This item fits the following BMW Chassis:
E83 X3,E85,E86,E89 Z4

Servicing your rear differential at regular intervals is important to ensure you maintain both performance and a long lifespan. Over time, the differential fluid can break down, lose its lubricating properties, and become contaminated with metal shavings and debris. Regularly replacing the fluid ensures that the gears and limited slip differential clutch packs are adequately lubricated, reducing wear and tear. Regular maintenance also helps identify potential issues before they become major problems.

This kit includes Genuine BMW differential fluid designed specifically for your M Sport differential and a brand new fill plug. The factory plugs include a rubberized seal that compresses over time and may not seal properly when reused.

One unique aspect of performing this service is the removal of the lower differential temperature sensor. Unlike many typical BMW differentials, this differential does not use a traditional drain plug and instead uses the temperature sensor as a drain plug. This sensor is removed to drain the differential fluid and is replaced before refilling. If you'd like to replace this sensor as well (not included in this kit), please see our recommended items or search BMW part number 33107847469.

NOTE: This kit includes 3 500ml bottles of diff fluid. BMW claims that only 1 Liter of fluid is necessary, but we found that 2 500ml bottles were insufficient. The third bottle included also allows for a minor flush of the old differential fluid before refilling.