Improper Tooth

Contact (Mesh)

X times Gear Tooth Count

radial, axial

steady, sometimes with beats

narrow band

Often with 1X of either gear sidebands

Gear Eccentricity

1X, tooth mesh

radial

narrow band

Gear may be balanced but mounted on an unbalanced rotor.

1X sidebands around tooth mesh are present

Gear Misalignment

2X, tooth

mesh

axial

steady

narrow band

1X sidebands around mesh rate

Pitch Line Runout,

Mass Unbalance or

Faulty Tooth

1X plus tooth mesh frequency

radial for spur gears

plus axial for single or double helical

steady

narrow band

1X sidebands around tooth mesh

Machining Errors

tooth mesh, "Ghost" frequency, usually not synchronous with 1X

radial, axial

steady

narrow band

Machining errors due to hobbing and cutting table drive gear mesh problem can cause "ghost" component.

Planetary Gear

Problems

Strongly dependent on gearbox geometry

radial

steady

narrow band

Sidebands around tooth mesh spaced at planet orbiting rate are common.