The larger body of "English rolled" aluminum was also similar in appearance to the smaller and successful Lotus 11, with a major difference of a full-width windscreen, and the lower scuttle/screen height.

Lotus 15's debut was in Sussex Trophy at Goodwood on 7 April 1958 in the hands of Graham Hill who immediately set the lap record, but failed to finish the race due to a gearbox problem.

This constant mesh, sequential-shift, 5 speed gearbox combined with ZF limited-slip differential in the transaxle configuration was compact, light (85 lbs including inboard brakes and halfshafts) and quick shifting, but the reliability problem had been carried over from the F1 and F2 Lotus 12 single seater.

Colin Chapman hired a young and talented gearbox engineer, Keith Duckworth, to solve this problem, but the priority needed to be on Lotus 16 for Grands Prix, which shared the Queerbox problem, so a newer version Series 2 was born while the update was in development in July, 1958 with BMC B-series four speed gearbox attached directly behind the engine, and a conventional differential housing with brake disc calipers mounted on the sides.

By the time the Series 3 was born in 1959, the Lotus transaxle had become more reliable thanks to the Duckworth redesign on its own dry sump lubrication system, but the young engineer pointed out the inherent limitation of the box in the amount of torque it can safely handle.