BMW M3 F80 M4 F82 Transmission Manual Gearbox GS6-45BZ 23007858800

Part Number: 23007858800 (Replaces 23007849615)

Model Code: GS6-45BZ – THA9 (Option S2MA)

The GS6-45BZ is the reinforced 6-speed manual gearbox engineered by ZF for the high-torque $S55$ biturbo engine. Found exclusively in the M3 (F80) and M4 (F82/F83), this transmission is a specialized evolution of the standard F30 units, featuring upgraded internals to handle the $550\text{ Nm}$ of torque and the $7600\text{ RPM}$ redline of the M-power powerplant.

Technical Specifications

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

  • BMW M4 (F82/F83): 2014–2020

• Torque Rating: Officially rated at $600\text{ Nm}$, though physically identical to units tested for higher loads in performance applications.

• Weight: ~45 kg (99 lbs), contributing to the Manual M4 being significantly lighter than its DCT counterpart.

• Clutch Compatibility: Designed for the M-specific Twin-Plate Clutch and Dual-Mass Flywheel.

Key Performance Engineering

• Carbon-Fiber Synchronizers: Unlike standard gearboxes, the M-spec GS6-45BZ utilizes carbon-fiber friction linings on its synchronizer rings. This allows for faster, more heat-resistant gear synchronization during aggressive high-RPM shifting.

• Dry Sump Lubrication System: This variant features an internal oil spray system that actively lubricates the gear meshes. This reduces “churning losses” and ensures consistent lubrication under high lateral $G$-forces that would otherwise push oil away from critical components.

• Auto Rev-Match (Speed Sensor): The gearbox includes an integrated gear-position sensor that communicates with the DME (Engine ECU). This enables the automated heel-toe blip during downshifts when the vehicle is in Efficient or Sport modes.

• Optimized Ratios: The gear spreads are engineered to keep the $S55$ biturbochargers in their peak boost window between shifts.

Professional Installation & Cataloging Notes

When preparing this transmission for inventory or a swap, observe the following technical standards:

1. DME Calibration: If retrofitting this unit into a car that was previously a DCT, the DME must be flashed with the manual software profile to enable the rev-match functionality and cruise control logic.

2. Fluid Specification: This unit requires BMW MTF-LT-5. It is critical not to use older LT-2 or LT-3 fluids, as the chemical additives are specifically matched to the carbon-fiber synchronizer linings.

3. Driveshaft Compatibility: The manual transmission is physically shorter than the DCT. A manual-specific driveshaft and shifter linkage assembly must be used for a successful installation.

4. Condition Check: Inspect the Input Shaft for any play and ensure the Gear Position Sensor (located on top of the housing) is undamaged, as this sensor is vital for the car’s electronics to understand which gear is selected.

Component Note: A complete “Swap Set” should include the transmission, the M-specific shifter carrier, the dual-mass flywheel, and the twin-plate clutch assembly.