The bang heard and felt when torque reverses through a gear train and teeth cross their backlash to hit the other flank. It shows up on throttle tip-in, when shifting into drive or reverse, and when a machine reverses direction. Some clunk is normal, but a growing one signals worn teeth, worn splines, loose yokes or bearings, with excess lash adding up along the whole driveline.
Clunk going into reverse got worse, check yoke spline wear before you blame the gears.
Also heard as
- driveline clunk
- lash clunk
Related terms
Lash
Shop clipping of backlash, the free play between mating gear teeth, as in set the lash or check lash.
Slop
Shop word for too much play in a gear train or drive, felt as free movement before anything turns.
Backlash
The play between mating teeth: how far one gear can rock before its teeth contact the other gear's teeth.
Rattle
A clattering noise from unloaded gears bouncing back and forth inside their backlash.