Automatic Fire Transmission That Brings Otherworldly Performance To the Common Man.
The last thing you want to do when driving a performance car near its dynamic limits is take your hands off the steering wheel. As much as an expert command over the left pedal and stick shifter can stroke the ego, automatic transmission is a much more sensible way to handle torque in excess of 400 N.m. Mercedes-Benz knows this and has been offering variations of the planetary transmission on all of its Mercedes-AMG cars since the 1993 C36.
The Speedshift MCT is the finest example to date – on any car. To be honest, the MCT (multi-clutch technology) transmission isn’t new. Having first been available on the 2009 SL 63, it’s been around a long time.
What sets this autobox apart is a complete abandoning of the torque converter in favor of a compact multi-plate wet clutch for getting off the line. This innovation allows for similar 4 000 r/min race starts as experienced on, say, the Lamborghini Huracan. The crowning achievement, from a Mercedes point of view, however, is that the gearbox weighs in at a minuscule 80kg thanks to its magnesium casing.
Other things the Merc guys keep raving about are things such as the higher power density (which means it’s smaller than the DCT it replaces, while offering no power- train drawbacks) and the small center tunnel needed to squeeze in the gearbox – a design requirement that Mercedes-Benz takes particular pride in.
We were more concerned about the brains of the car. The AMG Drive Unit combines all the sensor and control input and adjusts the shift logic according to driving conditions. On the Mercedes-AMG C63 S (note the combined Merc and AMG nomenclature; this means that cars don’t get sent to be tuned, but rather cars are developed as a partnership from scratch) you get four driving modes: C, S, S+ and Race.
The C is for Controlled Dynamics and opts for higher gearing to increase fuel efficiency and limit engine noise. On kickdown though, the transmission will shift down as many as three ratios to give instant, sporty response.
When you’re in the S modes, the transmission performs automatic double declutches and preselects the next gear for quick changes (Merc claims as swift as 100 milliseconds), with shift speeds depending on throttle input. You can also shift manually via the paddles and get as near as makes no difference to the redline – we did experience a few downshift rejections when the computer decided the engine speed was too high.
Race mode comes with the launch control ritual that needs synchronized paddles and some foot shuffling. But the squealing race start and being jammed into the seat-back are your reward.
With enough technology built in to make any technophile weep with joy, it should come as no surprise that the car’s radar (the bit that makes active cruise control possible) also feeds into the AMG Drive Unit’s thought process. If you go barrelling up behind another car, the radar will alert the system and engage a double downshift according to your braking power to add some torque drag to help you stop sooner. The harder you brake, the earlier the downshift.
It’s astonishing that Mercedes has experienced zero failures in testing or in the field with the Speedshift MCT when you consider the type of cars the transmission has been deployed in. And while that streak continues, this can be considered the best automatic transmission on the market today.