A precast concrete supplier reported that a JLG 1055 telehandler's telescoping boom exhibited noticeable lateral play when a heavy load was suspended. When the operator raised and extended the boom with a 4-ton load, the boom visibly bounced and swayed laterally, making precise placement difficult. A metallic scraping noise was also audible during boom extension.
The technician first measured the boom's lateral play at full extension by attaching a dial indicator to the boom tip and applying lateral pressure. The play measured 12 millimeters (spec is under 3 millimeters), confirming excessive clearance between the boom sections. He then inspected the "Boom Wear Pads"-the replaceable UHMW-polyethylene sliding pads mounted to the inner surfaces of each outer boom section, which support and guide the telescoping stage as it extends.
Upon visual inspection, several of the wear pads had worn through to less than 2 millimeters of remaining material (spec minimum is 5 millimeters), and two pads had completely disintegrated, exposing the boom's inner rail surface to direct metal-on-metal contact with the outer boom section. The metal-on-metal contact had scored the inner rail surface with deep grooves and had produced the metallic scraping noise.
The root cause was traced to missed preventive maintenance. Wear pads are consumable items designed to be periodically replaced as they wear, but the telehandler's service history showed no record of wear pad inspection or replacement over 6,000 operating hours. Additionally, the pads had been operating without lubrication-the pad rails had dried out, accelerating friction wear.
The repair involved replacing all 12 boom wear pads with new UHMW-polyethylene pads, machining the scored boom rails to remove the surface grooves, and applying a dry-film lubricant coating to the pad rails to reduce friction wear. The boom's lateral play was re-measured after pad replacement and found to be 1.5 millimeters-well within specification. The load-induced bouncing disappeared, and the metallic scraping noise was eliminated.
