Design. The original idea behind straight-cut gears (cut at 90 degrees across the gear) was really ease of manufacture. Where limited numbers of gears are made for development – be it standard or motorsport – straight-cut gears are far cheaper and easier to produce. A multitude of gear ratio options being available by ‘correcting’ proper tooth profiles to suit - excruciatingly difficult and not economically viable with helical teeth where very much more expensive tooling’s needed. Other bonuses were reduced loads and drag inherent in the helical (cut at an angle across the gear) design – therefore leaving more power to drive the car. That straight-cuts are stronger than helical gears is a myth. Helical cut teeth run quieter as they’re almost constantly engaged, also eliminating shock loads. They’re stronger through better tooth root design and more load-bearing area – the helical angle increasing overall tooth length and surface area by a small but appreciable amount.