The pure-tone gear noise heard at mesh frequency and its harmonics, which climbs in pitch as speed rises. It comes from transmission error, the small fluctuation in motion each time teeth hand off load, and it varies with load, so many boxes whine only on drive or only on coast. Fixes include better tooth accuracy, profile and lead modification, higher contact ratio and stiffer housings.
Whine's only there under power between forty and fifty, so it's a pattern or a lash issue in the rear, not a bearing.
Whine that changes between drive and coast points at a flank; noise that ignores load direction is more often a bearing.
Also heard as
- gear whine
- gear noise
Do not mix it up with
- Rattle: Rattle is a random knocking from unloaded teeth bouncing in their backlash, not a steady tone.
Related terms
Transmission error
The tiny difference between where the output gear actually is and where a perfect gear pair would put it.
GMF
Gear mesh frequency: tooth count times shaft speed, the frequency at which teeth enter mesh.
Howl
Shop word for a loud, droning gear noise, usually from a vehicle axle with a worn or badly set ring and pinion.
Tip relief
A slight removal of material near the tooth tip so each tooth enters mesh smoothly under load.