The swing bearing (or slewing ring) connects the upper house to the undercarriage. It handles every rotation, every load, every shock. When it fails, replacement costs tens of thousands and requires splitting the machine. Most swing bearing failures start small. Here are four checks that catch trouble early.

1. Measure Vertical and Radial Play

Excessive play in the swing bearing means internal wear. With the excavator parked on level ground, place a dial indicator against the outer race (or use a feeler gauge method). Push the upper house sideways with the boom and measure radial movement. Then lift the machine with the boom and measure vertical lift. For a 20‑ton excavator, vertical play above 3mm or radial play above 2mm indicates the bearing needs replacement. Check play every 1,000 hours. Record measurements to track wear rate.

2. Grease the Bearing on Schedule

The swing bearing needs fresh grease at regular intervals — typically every 50 operating hours for normal use, and every 25 hours in dusty or wet conditions. Rotate the house slowly while pumping grease into the fitting until you see fresh grease purging from the seals. If old grease comes out dark or gritty, the bearing is contaminated. If no grease purges from one section, the grease channel may be blocked — clear it with a wire before forcing grease, which could damage seals.

3. Inspect the Seal Strips

Rubber or polyurethane seal strips run around the top and bottom of the bearing. They keep dirt and water out. Walk around the machine and inspect both seals. Look for gaps, tears, or sections that have come out of their grooves. A damaged seal lets sand and water into the bearing race, accelerating wear. Replace seal strips immediately — they are inexpensive and easy to install compared to bearing replacement.

4. Listen for Changes in Swing Sound

Every operator knows the normal sound of the swing motor and bearing. A change is a warning. Grinding, popping, or irregular clicking during rotation often means damaged rollers or race spalling. Also check for jerky swinging or uneven rotation speed, which may indicate internal damage. If you hear unusual noises, stop swinging and inspect the bearing visually for play or grease contamination. Do not continue working — a seized swing bearing can twist the turntable frame beyond repair.

Quick field check: With the engine off, swing the house slightly by hand (use a pry bar against the track) and feel for roughness. Smooth, consistent movement is good. Any catching or notchiness means the bearing is failing internally.

Want a swing bearing inspection log sheet for your excavator? Reply with your machine model and serial number — we will send a PDF with play measurement procedures, grease specifications, and a maintenance log template.