BMW M3 F80 M4 F82 F83 Transmission DKG Dual Mass Flywheel

Part Number: 21212284348 (Standard for F80/F82/F83 M-DCT)

Manufacturer: LuK (Original Equipment Manufacturer)

The Dual-Mass Flywheel (DMFW) for the M-DCT (DKG) transmission is a critical dampening component situated between the $S55$ engine and the GS7D36SG dual-clutch gearbox. Unlike a traditional manual flywheel, this unit is specifically engineered to handle the rapid-fire torque interruptions of a dual-clutch system while isolating the sensitive mechatronics from engine vibrations.

Technical Specifications

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

  • BMW M4 (F82/F83): 2014–2020

• Engine Match: BMW $S55$ (3.0L Inline-6 Twin-Turbo).

• Transmission Match: 7-Speed M-DCT (Double Clutch Gearbox).

• Construction: Two independent masses connected by a complex internal spring and damping system.

Key Engineering Functions

• Vibration Isolation: The $S55$ engine produces significant torsional vibrations. The DMFW absorbs these oscillations before they reach the transmission, preventing “gear rattle” and protecting the dual-clutch’s internal synchronizers.

• Crankshaft Protection: By absorbing the shock of lightning-fast DCT shifts (especially in Drivelogic Mode 3), the flywheel reduces the stress on the crankshaft main bearings.

• Rotational Inertia: Precision-weighted to ensure the engine revs freely (essential for the M4’s 7,600 RPM redline) while providing enough mass to maintain a smooth idle and low-speed “creep” functionality.

Professional Installation & Diagnostic Notes

When handling this component for inventory or replacement, keep the following technical points in mind:

1. Wear Limits (Rocking/Rotational Play): A used DMFW must be tested for “play.” There is a specified limit for both rotational movement (free travel) and tilt (rocking). If the internal springs are fatigued, you will hear a distinct “clunking” or “chatter” at idle that disappears when the transmission is engaged.

2. One-Time Use Hardware: The 8 mounting bolts (M10 or M12 depending on production date) are stretch bolts. They must be replaced during every installation to ensure the flywheel does not back off the crankshaft.

   • Torque Spec: Typically $60\text{ Nm} + 90\text{°}$ (Always verify with current ISTA data for the specific VIN).

3. Pilot Bearing: Always inspect or replace the pilot bearing located in the center of the flywheel. A seized bearing can cause the DCT to have difficulty disengaging the clutches, leading to rough shifting or “creep” issues.

4. Resurfacing Warning: Never resurface a Dual-Mass Flywheel. The internal grease and spring mechanisms cannot withstand the heat of a grinding machine, and the debris from resurfacing can enter the internal dampening chamber, leading to total failure.

Inventory Tip: If selling a used DKG transmission, the DMFW is often sold separately. However, bundling it as a “complete clutch/flywheel set” is highly recommended for buyers performing a conversion or major overhaul.