From TechnoDocs
Ball nut preload is the amount of pressure the housing exerts on the mechanics (typically ball bearings)in a ball nut.
Overtightening the preload on a ball nut will cause:
- Premature wear of the ball nut and screw
- Overheating of the motor
Undertightening of the preload on a ball nut will cause Backlash.
Do not attempt to tighten preload on a ball nut unless you are directed to after contacting support.