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Doorbusters 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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Doorbusters - Corporate Logo
T#:34851776
Part#: 049424LADBKT
Ships in 1-2 days
$ 1,250.99 USD
Free Shipping
$ 1,250.99 USD
Free Shipping

Take your E36’s performance to the next level with the exclusive Turner Motorsport Doorbuster! This limited-time bundle combines two essential drivetrain upgrades: a Turner Motorsport E36 188mm Reinforced Billet Aluminum Differential Cover, engineered for superior durability and cooling, plus a set of ECS polyurethane transmission mounts for better power transfer and stability. Elevate your ride’s reliability and driving experience with this all-in-one kit.

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.

Whether you’re upgrading your daily driver or prepping for track days, this Turner Motorsport Doorbuster Kit delivers durable components engineered for serious enthusiasts. Boost your E36’s durability, cooling capacity, and drivetrain stability—all while enjoying the benefits of a truly performance-focused setup.

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Doorbusters - Corporate Logo
T#:47439408
Part#: 025993LADBKT
Ships in 1-2 days
$ 1,300.00 USD
Free Shipping
$ 1,300.00 USD
Free Shipping

For a limited time, get two ECS Heavy Duty differential bushings FREE with the purchase of our Dual-Mount Differential Cover Kit—the ultimate rear-end upgrade for your high-output E30 build. Engineered for strength, cooling, and reliability, this kit is the go-to solution for enthusiasts pushing their car on the track, drift events, or the drag strip.

Turner Motorsport Heavy Duty Dual Mount Differential Cover – E30

Stop worrying about weak factory differential mounts! The OEM E30 differential cover has only one mounting point, which can fail under high torque or boosted applications. Turner’s dual-mount billet aluminum cover solves this problem by adding a secondary mounting ear secured to the chassis via a billet plate and sheet metal bracket—either bolted for easy installation or welded for ultimate rigidity.

Crafted from 6061-T6 billet aluminum and finished with black hard coat anodizing, this cover is 30% stronger than stock and engineered for maximum durability. It also features large CFD-optimized cooling fins and a built-in air duct to reduce fluid temperatures, ensuring consistent performance and long fluid life. Optional -6AN fittings allow integration with an external cooler, and a 1/8 NPT port supports fluid temperature monitoring.

Key Features:

Dual reinforced mounting points with integral sheet metal bracket and billet plate for extreme durability

Secondary mount can be bolted or welded to chassis for added rigidity

Large external fins designed via CFD for efficient heat dissipation

Integrated air duct for improved airflow and fluid cooling

Breather system to vent pressure properly

1/8 NPT sensor port for real-time differential temperature monitoring

Maintains compatibility with OEM, aftermarket, or performance E30 differential bushings

Accommodates large rear sway bars and upgraded suspension setups

Removable air duct allows easy access to fill/drain plugs and sensor bungs

ECS Heavy Duty Rear Differential Bushings

Factory rubber bushings are soft, allowing unwanted differential movement that creates a disconnected feel, excess noise, and reduced performance. ECS Heavy Duty rear differential bushings solve this problem with a stiffer HD 70D rubber compound and aluminum center sleeve, locking down your differential while keeping NVH levels manageable for street driving.

Benefits:

Enhanced Responsiveness: Reduces deflection for a more direct drivetrain feel

Street & Track Friendly: HD rubber absorbs vibration but remains firm under performance conditions

Replaces Weak OEM Mount: Ideal for aging or cracked stock bushings

Easy Installation: Precision-manufactured to OEM specifications for a direct bolt-in fit

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Doorbusters - Corporate Logo
T#:34114216
Part#: 049409LADBKT
Ships on Dec 1, 2026
$ 1,446.97 USD
Free Shipping
$ 1,446.97 USD
Free Shipping

Looking to upgrade your drivetrain for durability and performance? The Turner Motorsport Billet Differential Cover Kit, paired with ECS Tuning's Polyurethane Transmission and Differential Mounts, offers the ultimate solution to eliminate drivetrain flex and enhance your BMW M3’s strength. Perfect for street or track use, this kit ensures top-tier performance for your E46 M3.

Turner Motorsport Billet Differential Cover Kit with ECS Polyurethane Differential Bushings

Engineered for strength and designed to handle extreme conditions, the Turner Billet Differential Cover is built from a single piece of 6061 billet aluminum and finished with a hard-coat anodizing for durability and corrosion resistance. It’s reinforced with mounting ears that prevent common failures seen with OEM diff covers, ensuring stability even during aggressive driving.

This high-performance cover features internal cooling fins that help dissipate heat, keeping the fluid cool and prolonging the life of your differential. It also maintains continuous lubrication of the ring gear, preventing fatigue and heat buildup. The cover is compatible with stock and aftermarket bushings, and comes with upgraded -6AN drain and fill plugs for easy maintenance or for expanding to an external oil cooler. A 1/8 NPT fitting is also included, making it easy to install a temp sensor and keep an eye on fluid temperatures.

Key Features:

Reinforced mounting ears: No more broken diff cover ears. Cooling optimized: External and internal fins reduce heat buildup. Increased capacity: Holds more fluid for better performance. Oil cooler ready: -6AN ports for external cooler installation. 1/8 NPT provision: Easily add a temp sensor. Sight glass: Check fluid level without removing plugs. Compatibility:

Fits E46 M3 with large case 210/215mm differentials. Designed for stock, polyurethane, or solid differential bushings. Accommodates OEM speed sensor and wire mounts. ECS Tuning Polyurethane Transmission Mount Set

Tired of soft factory transmission mounts causing mis-shifts or excessive movement? ECS Tuning’s Polyurethane Transmission Mount Set is the solution. With a durable 70A durometer rating, these mounts offer the perfect balance between everyday comfort and track-ready stiffness. For more track-focused drivers, we also offer an 80A durometer option.

These mounts feature a mechanical interlock design, ensuring longevity even in high-torque applications. Resistant to oil, water, and heat, polyurethane lasts longer than rubber and significantly reduces drivetrain deflection, improving power delivery and driving engagement.

Key Features:

Reduces transmission movement: Minimizes mis-shifts and over-revs. Polyurethane construction: Durable, with superior wear resistance. Two options: Choose between 70A for daily driving and 80A for track use. Engaging driving experience: More connected feel between driver and drivetrain. Upgrade your E46 M3 with this robust kit, and bulletproof your drivetrain today! Perfect for enthusiasts pushing their cars to the limit on the street or track.

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