BMW Differential and Gearing Upgrades for BMW 3 Series E30 (1984-1991)

Designed for track drivers, drift enthusiasts, and drag racers alike, this all-in-one driveline upgrade eliminates the factory weak points and reinforces your drivetrain for high-performance abuse. Whether you're laying down 500HP, clutch-kicking through corners, or launching hard at the strip, this cover keeps your differential secure, cool, and ready for battle.

The stock E30 differential cover features a single mounting provision—fine for a stock M20, but guaranteed to fail on your boosted high-horsepower M5X build. After years of broken covers, mounting tabs, and dreams, our team of E30 enthusiasts engineered the ultimate fix.

Unlike the brittle OEM cast aluminum cover, our upgraded differential cover is CNC-machined from 6061-T6 billet aluminum, offering a 30% increase in material strength alone. More importantly, a secondary mounting ear has been integrated into the design for added support, drastically improving stability and driveline shock absorption. The secondary mount is tied into the chassis using a reinforced sheet metal bracket and a billet aluminum plate, allowing for bolt-on installation or welding for ultimate rigidity.

Another major flaw of the factory E30 differential cover is its lack of any cooling provisions, leading to overheated fluid and premature wear. Our engineers solved this issue by incorporating advanced cooling features into the design. Large external fins have been added to the cover, and are optimized using CFD (Computational Fluid Dynamics) analysis to efficiently dissipate heat, reducing overall fluid temperatures. By maintaining a more stable differential temperature, this cover ensures consistent performance and extends the lifespan of your differential fluid. A built-in air duct assists in cooling by increasing airflow around the differential, further preventing heat-related failures. Our cover features optional -6AN fittings, allowing for easy integration of an external fluid cooler if desired. Finally, a 1/8 NPT port is included with the kit to ensure compatibility with fluid temperature monitoring systems.

Precision-machined from 6061-T6 billet aluminum and finished with a black hard coat anodizing, this cover is built to withstand hard use. Despite its robust construction and superior durability, this differential cover retains factory mounting features. This means any E30 188mm differential cover bushing can be installed, allowing you to tailor our upgraded cover to your build. The cover also accommodates large rear sway bars, ensuring fitment on cars with upgraded suspension. Our proprietary removable air duct provides easy access to sensor bungs, fill plugs, and drain plugs, making differential service a breeze.

FEATURES

Unmatched Strength & Durability - Heavily reinforced mounting locations are designed to withstand extreme horsepower, torque, and shock load. Secondary Differential Mount - A built-in secondary mount, integral sheet metal bracket, and billet adapter plate make this the strongest E30 differential cover on the market. Bolt-On or Weld-On Installation - The secondary mount is designed for easy bolt-in installation or can be welded to the chassis for ultimate rigidity. Optimized Cooling - Large external fins, designed using CFD analysis, dissipate heat efficiently, reducing overall differential fluid temperatures. Integrated Breather System - An integrated breather system reduces internal cavitation by properly venting built-up pressure. Enhanced Fluid Management - Includes a 1/8 NPT sensor port for real-time fluid temperature monitoring, and optional -6AN fittings for adding an external fluid cooler. Aerodynamic Air Duct - The included aerodynamic air duct further reduces fluid temperatures, increasing fluid service life and reliability. KIT CONTENTS

Dual Mount Differential Cover Assembly Includes the cover, sheet metal mounting bracket, billet aluminum mounting plate, and aerodynamic air duct. Installation Hardware Kit Includes everything you need to install this masterpiece on your E30! Differential Gasket Choose between a Genuine BMW paper gasket or make your own gasket with Loctite 5970. Optional -6AN fittings (2) for adding an external fluid cooler. Differential Cover Bushings Choose between Powerflex, OE MOOG, and Genuine BMW, or add your own (two E30 188mm differential cover bushings required for installation). Gear Oil Choose between Liqui Moly, Redline, and Genuine BMW, or supply your own fluid for reassembly.

This factory finned differential cover bolts directly to the E30 diff housing. This is a must for track cars with limited slip differentials. The clutch packs in these diffs generate a lot of heat, the more heat you can dissipate the better. The fins on this cover will do just that. This is an inexpensive upgrade that may save you a lot of money down the road. Plus it looks cool.

Kit includes cover, gasket and all necessary hardware.:

• 1 x 33112228335 - Differential Cover
• 1 x 33111210405 - Differential Gasket
• 2 x 07119914114 - Bolt
• 4 x 07119921522 - Bolt
• 2 x 07119921541 - Bolt

The following photo of the cover with bushing is just representation of this kit. 

This item fits the following BMWs:
1984-1991 E30 BMW 325e 325es 325i 325ic 325is M3

If your differential is leaking fluid, this is the likely cause. Restore the tight seal with this Genuine BMW seal to prevent potential damage or future failure.

Fits the following BMW Chassis:
E30, E36, E28, E34, E24, E23, E32, E38, Z3