What Car? Q&A - Tell me about BMW's automatic gearboxes

Q: How do BMW's automatic gearboxes differ, and which one is the best choice?
Joe Harvey

A: BMW offers more than one alternative to a manual gearbox on its current cars. Some, however, are exclusive to specific models.

The main automatic gearbox BMW offers is called the Steptronic made by ZF. This is BMW's traditional automatic, which shifts relatively effortlessly between ratios in either normal or sport modes. The driver also has the option of operating the gears by nudging the lever forward and rearwards to shift up and down respectively.

All new automatic BMWs have a six-speed version of this gearbox. However, the 3 Series coupe and cabriolet are only available with a five-speed version until the replacement arrives late next year or early 2007.

BMW also offers the Sequential Manual Gearbox (SMG), fitted as standard to the M5 and M6, and optional on the M3, 530i and 545i. There is also a tamer version available on the 550 and 650 models.

The SMG is not strictly an automatic gearbox; this system uses a hydraulically operated clutch which is activated when the driver selects a different gear. In automatic mode, each gear change is similar to a manual, in that the car physically changes through the gears itself.

The SMG has been criticised for lacking in smoothness, but selecting manual mode improves the gearchange. Some versions of the SMG are available with steering wheel-mounted paddles in addition to the gear lever on the transmission tunnel.