Worm gear. Historical artwork of a worm gear or endless screw devised by Leonardo da Vinci (1452- 1519) about 1490. The worm gear consists of a toothed wheel (at centre) which is worked by a short, revolving cylinder (at upper centre) known as the worm. There is a weight attached to the toothed wheel. This type of gear transmits power between perpendicular shafts. Worm gears are used in modern rear-wheel drive car transmissions.