BMW M3 F80 M4 F82 M2 F87 Differential rear axle gear 2289970

Part Number: 2289970 (HAG 215 L)

Type: Electronically Controlled Limited-Slip Differential (LSD)

The 2289970 is the high-performance rear axle final drive designed specifically for the F80 M3, F82/F83 M4, and the F87 M2/M2 Competition. Unlike a traditional mechanical LSD, this “Active M” unit uses an electric actuator to vary the locking torque from $0\%$ to $100\%$ in milliseconds, providing unparalleled traction and “drift-ability” characteristic of the F-chassis M cars.

Technical Specifications

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

  • BMW M4 (F82/F83): 2014–2020

  • BMW M2 (F87): All models including Competition and CS.

• Final Drive Ratio: $3.46:1$ (Standard for both Manual and DCT models).

• Control Unit: Interfaces with the GHAS (Regulated Rear Axle Differential Lock) control module.

• Internal Mechanism: Multi-plate clutch pack with an integrated electric motor actuator.

Key Performance Features

• Predictive Locking: By analyzing steering angle, throttle position, brake pressure, and wheel speeds, the differential can lock before a wheel starts to slip, stabilizing the car during aggressive turn-entry.

• Dynamic Stability Integration: It works in tandem with MDM (M Dynamic Mode). In high-performance settings, it allows for controlled oversteer by precisely managing the torque split between the left and right rear wheels.

• Thermal Management: The housing features prominent cooling fins to dissipate the extreme heat generated by the clutch plates during track use or heavy drifting.

• Hollow Input Shaft: Designed for weight reduction while maintaining the structural integrity required to handle the $550\text{+ Nm}$ of torque from the $S55$ engine.

Technical Installation & Maintenance

This is a highly sensitive electronic component. For professional inventory or installation, adhere to these guidelines:

1. GHAS Calibration: If replacing the differential, the GHAS control module must be “learned” to the new unit via BMW ISTA. The module needs to calibrate the motor’s “zero point” and the clutch thickness characteristics to ensure smooth engagement.

2. Fluid Requirements: This unit requires BMW Final Drive Gear Oil SAF-XJ. Note that it uses a specific friction modifier for the carbon-fiber-reinforced clutch plates. Using standard gear oil will cause “chatter” and premature plate wear.

3. Oil Capacity: Approximately $1.1$ Liters. It is a “fill-to-spill” system—fill until the fluid reaches the bottom of the fill plug hole while the vehicle is level.

4. Hardware Note: The rear differential is mounted to the subframe using high-torque bolts. BMW recommends replacing the Output Shaft (Axle) Bolts and the Driveshaft Nut upon reinstallation to prevent loosening under high torque loads.

Warning: When sourcing used units, check for leaks around the Input Shaft Seal and the Electric Actuator Connector. Physical damage to the aluminum cooling fins can also lead to overheating during track sessions.