Common Signs of Damaged Swing Bearing

The swing bearing, also known as slewing bearing, is the critical component that lets an excavator rotate its upper structure smoothly. It carries heavy axial, radial and tilting loads all day long. With constant shock, dust, water intrusion and poor lubrication, it will wear out gradually. If you ignore early warning signs, you may face sudden breakdown, costly repair and longer downtime.

Below are the most common signs telling you your swing bearing is damaged and needs inspection or replacement.

Strange grinding, creaking or rumbling noise while slewing is usually the first noticeable signal. When the raceway or rollers get pitted, rusted or worn, metal friction creates continuous abnormal sound. The noise often gets louder when you turn the cab under heavy load or on uneven ground. If you hear knocking sounds during rotation, the damage is already serious.

Excessive play or loose swing is another clear indicator. When you stop rotation and push the boom, you can feel obvious wobbling and clearance. Too much backlash means the internal rolling elements and raceways have lost their original precision. Loose slewing movement will hurt other connected parts such as gears and hydraulic motors.

Oil leakage around the slewing circle should never be overlooked. Broken seals allow grease or hydraulic oil to leak out. Meanwhile, dirt, sand and moisture go inside the bearing assembly. Leaking grease is not only a waste of lubricant; it speeds up corrosion and abrasive wear inside the raceway.

Stiff rotation or stuck swing happens in the middle stage of failure. The excavator does not turn smoothly. Sometimes it jerks, or gets stuck at certain angles before moving again. This usually comes from worn rollers, deformed raceways, contaminated grease or rust buildup inside the swing bearing.

Visible rust, cracks and surface damage can be found during regular maintenance. Check the exposed race surface and seal area. If you spot rust lines, surface peeling, cracks or broken guard strips, the slewing bearing cannot work for much longer.

Increased swing pressure and overheating are easy to miss. Your operator may notice the machine needs more power to slew, and the slewing assembly runs hotter than normal. Extra working pressure puts extra burden on the swing motor and hydraulic system, which may trigger further hydraulic faults.

Many machine owners keep running the excavator even after these symptoms show up, trying to save cost temporarily. In fact, delayed replacement often leads to broken teeth on the internal gear, damaged swing drive and far higher repair bills.

If you observe any of these signs, stop heavy operation and inspect the slewing bearing at once. When replacement is required, confirm the OEM part number, dimension, gear type and seal style before ordering.

ZHZB provides reliable aftermarket swing bearings for Komatsu, Caterpillar, Volvo, Hyundai, Sany, XCMG and other construction machinery. All our slewing bearings are strictly inspected for load capacity, sealing and wear resistance. Send us your part number to get a quick quotation.