BMW M2 F87 M3 F80 M4 F82 6-speed manual transmission GS6-45BZ 7858800

Model Code: GS6-45BZ (Option S2MA)

The GS6-45BZ is the heavy-duty 6-speed manual gearbox engineered by ZF for the high-torque $S55$ biturbo engine. Found in the M2 Competition (F87), M3 (F80), and M4 (F82), this transmission is a favorite among enthusiasts for its mechanical engagement and “rev-matching” technology. Despite the prevalence of the DCT, this manual unit is increasingly rare and highly valued for analog driving builds.

Technical Specifications

• Compatibility: * BMW M3 (F80) $2014$–$2018$

  • BMW M4 (F82) $2014$–$2020$

  • BMW M2 Competition (F87) $2019$–$2021$

• Torque Rating: Officially rated to handle up to $600\text{ Nm}$ ($443\text{ lb-ft}$), though it is known in the tuning community for its robustness under higher loads.

• Weight: Approximately $45\text{ kg}$ ($99\text{ lbs}$), offering a significant weight saving of roughly $25\text{ kg}$ over the M-DCT alternative.

• Key Feature: Integrated Auto-Rev Match (can be disabled by turning DSC off or via coding).

Performance Engineering

• Carbon-Fiber Friction Linings: To handle the rapid synchronization required by the high-revving $S55$ engine ($7600\text{ RPM}$ redline), the synchronizer rings utilize carbon-fiber linings. This provides superior thermal stability and smoother shifts under track conditions.

• Dry Sump Lubrication: This “BZ” variant utilizes a specialized oil spray system to reduce drag and ensure all gears are lubricated even during high-$G$ cornering, preventing oil starvation.

• Dual-Plate Clutch Compatibility: The input shaft and bellhousing are designed to accommodate the heavy-duty dual-plate clutch system required to transfer biturbo torque without slipping.

Technical Installation & Cataloging Notes

When managing this transmission for inventory or a conversion project, please note the following:

1. DME Integration: If retrofitting this manual into a car that was originally a DCT, the DME (Engine Control Unit) must be flashed with the manual software to ensure the rev-matching and cruise control functions work correctly.

2. Fluid Requirements: This unit requires BMW MTF-LT-5 (Manual Transmission Fluid, Lifetime 5). Using incorrect fluid can damage the carbon-fiber synchronizers and lead to notched shifting or gear grind.

3. Physical Dimensions: While the GS6-45BZ is used in several BMW models, the 7858800 variant features the specific bellhousing bolt pattern for the $S55$ engine block. It will not bolt directly to the $N55$ or $B58$ blocks without modification.

4. Peripheral Components: A complete swap set should ideally include:

   • The dual-mass flywheel and clutch pressure plate.

   • The manual-specific driveshaft (which differs in length from the DCT version).

   • The shift linkage and the interior boot/knob assembly.