Kubota KX040-4 Clunking Noise During Swing
Fault Codes & Symptoms
Clunking noise when starting or stopping swing. Related symptoms: - Grinding noise during swing. - Metal shavings in swing gearbox oil. - Jerky swing motion. Operator reports a loud clunk or pop when swinging the machine left or right, especially when starting or stopping the swing motion quickly.
Confirmed cause: Failure of the swing drive gearbox lower shaft bearing. Repair performed: Drained swing gearbox oil. Removed swing motor and gearbox assembly from the machine. Disassembled the planetary gearbox and found the lower shaft support bearing had collapsed, causing the planetary carrier to contact the ring gear. Replaced the failed bearing, seals, and damaged gears. Cleaned and inspected all other components. Reassembled gearbox, refilled with new oil, and reinstalled the assembly with new mounting hardware. Verification: After reassembly, the machine was started and the swing function was tested. The clunking noise was eliminated. The swing start and stop were smooth in both directions under no-load and loaded conditions. Technician notes: - The magnetic drain plug was key to the diagnosis. Always check it for debris. - The failure was likely caused by a lack of lubrication or contamination. The operator did not know when the swing drive oil had last been changed. - It was necessary to remove the belly pan and rotate the house to access all of the swing drive mounting bolts.