Channelling drive to the rear wheels is a standard six-speed manual gearbox. The Getrag-produced unit has been developed from scratch and is claimed to be 12kg lighter than the outgoing unit. Among its innovations is dry-sump lubrication, a double-plate clutch to handle the added torque loading, carbon-ceramic friction linings within the synchroniser rings and a blip function on downshifts. The individual ratios are also shorter than before.
Buyers will be able to choose an optional seven-speed M Double Clutch Transmission (DCT), again from Getrag, with remote paddle shifters. A development of the M5’s unit, it allows the driver to choose between manual and auto modes. Further features include launch control and a so-called smoky burnout setting, which permits a degree of wheelspin at low speeds. To help improve on-the-limit handling, it also receives stability clutch control, which opens the clutches when sensors detect understeer to reduce drive and bring it back on line.
Both gearboxes receive a stop-start function, brake energy regeneration and optimum shift indicator. Official figures reveal that DCT versions have a 40kg penalty, with the DCT-equipped M3 tipping the scales at 1560kg and the M4 at 1537kg.
In a new driveline development, the new M3 and M4 adopt a carbonfibre-reinforced plastic propshaft. Constructed as a single component with no centre bearing, it is claimed to bring a 40 per cent weight saving on the previous M3’s steel driveshaft while providing a reduction in rotating masses for better driveline efficiency.
The new driveshaft is allied to hollow output shafts at the rear within the Active M differential, which uses an electronically controlled multi-plate clutch to provide a varying degree of lock-up.
With an official 0-62mph time of 4.3sec in standard six-speed manual guise, the new M3 and M4 are 0.5sec quicker than their predecessors. The seven-speed DCT drops the 0-62mph time to 4.1sec. Top speed is limited to 155mph, although it can be raised to 174mph as an option.