Spur Gears vs. Helical Gears: Load-Bearing and Noise Differences

Gear teeth can be cut straight or at an angle, resulting in different performance characteristics. The two primary options are spur gears and helical gears.

Spur Gears

Spur gears have straight teeth cut parallel to the shaft axis. They are simple to manufacture and highly efficient, but they produce a characteristic whining noise at high speeds due to sudden contact between teeth.

Helical Gears

Helical gears have teeth cut at an angle, creating a helical path. This angle allows teeth to engage gradually, resulting in quiet operation and high load capacity. Helical gears are standard in passenger car transmissions, while spur gears are often used in race cars and heavy machinery.

Calculate ratios using our interactive automotive gear ratio calculator. For historical context, read our guide on the history of automatic transmission gear ratios.