APART from BMW's sequential manual gearbox functions (pictured above), another of the M3's highly sophisticated electronic systems is the variable M differential lock. More advanced than the traditional torque-sensing, self-locking diffs with up to 25 per cent locking action seen on previous M cars, the new system employs a shear pump, plunger and multi-plate clutch to transmit torque from one driving wheel to the other, according to available traction. Combined with M3's perfect weight distribution and finely tuned DSC, BMW says the silicon fluid-based system "gives the new M3 driving characteristcs previously regarded as quite impossible with a rear-wheel drive sports car particularly in winter".