The epitome of racing feeling in everyday traffic starts a new round. 35 years after the debut of the first BMW M3, BMW M GmbH presents the latest generation of its high-performance automobiles in the premium mid-size segment. Time to introduce the two new vehicles. In the #M3M4explained series, the developers have the floor.
Mastering curves! Dominik keeps an eye on aspects such as track, stability, or axle kinematics in his considerations. The BMW M developer is responsible for the engineering and integration of the rear axle. In the video, Dominik introduces the rear axle transmission and explains important details.
BMW M ENTHUSIASTS ASK, BMW M EXPERTS ANSWER.
How do you compute an efficiency of 98 %?
It was measured on a test rig by comparing the torque difference between input and output.
Where is the heat coming mainly from: from the differential or from the transmission itself?
The heat loss is mainly a result of the friction within the transmission itself. The diff lock only contributes a small amount.
Is there still a need of a 5.000 km run in like in the past?
The recommended break-in period lasts 2.000 km followed by a service where the rear differential oil is changed. Afterwards, it is recommended to increase speed levels continuously.
How long does the oil in the rear axle transmission last?
At 2.000 km, after breaking in the car, a first oil change is required. Further oil changes depend on the actual use case. Please, refer to your dealer with regards to maintenance programs.
Why does it need an adapter plate?
The adapter plate provides NVH (noise, vibration, harshness) decoupling of the differential towards the rear axle subframe which is rigidly mounted to the car body.
Why are there output shafts with different diameters? I don’t understand the point – how does it work?
The two rear output shafts are designed with different stiffness resulting in an optimized harmonic behaviour of both rear wheels and thereby increasing traction.
