8 speeds, sequentially shifted using three built-up Meccano servos. A pair of Meccano relays for each servo simplify the operation and obviate the need for any non-Meccano diodes in the limit switches.

The gearbox is less than 2" thick and is mounted on its side for the purposes of this display. In the model it will sit between the chassis rails of the truck. Hiding everything else in the model will be 'interesting'...