Lifting with the boom and undercarriage in the same position, such as repetitive curbside digging with an excavator, can put a dimple in the bearing race close to the uneven load.A compact or mini excavator is a tracked or wheeled vehicle with an approximate operating ... upon hydraulic cylinders. The excavator's slew (rotation) and travel functions are also activated by hydraulic fluid powering hydraulic motors.

If the turning torque of the bearing increases substantially, or if you notice a clicking or grinding noise when rotating the structure, grease the unit and have some of the purged lubricant analyzed for wear metals. Play or clearance in the bearing can indicate a problem and will show up as a lack of 'stiffness' in the extended boom. Free play magnified over the length of the boom allows it to rock back and forth under load. Check bearing clearance with a dial indicator that measures how much the structure tilts when the boom is loaded.