A logistics warehouse reported that a Toyota 8FBEU15 reach truck was making a "popping" noise when raising the mast, and the forks would tilt sideways at heights above 6 meters. The operator complained that the lift speed was slower than normal.
The technician first inspected the lift chains. The left chain was significantly tighter than the right chain. He then extended the mast and checked the "Mast Rail Clearance" using a feeler gauge. The inner rail (stage 2) had excessive side play (over 5mm) on the left side, and was tight on the right side.
He traced the root cause to the "Mast Shimming." The mast rails are separated by bronze shims (wear strips). Over time, these shims had worn thin on one side. The technician also found that the "Lift Cylinder Anchor Bolts" were loose. This allowed the cylinder to shift sideways, twisting the inner mast frame.
The "popping" noise was caused by the mast rollers binding against the rail edge as the twisted frame tried to straighten itself during extension. The uneven chain tension was a symptom of the frame twist.
The repair involved removing the inner mast and replacing all the wear shims with new PTFE-impregnated bronze shims. The technician then re-aligned the mast rails using a laser alignment tool, ensuring the distance between the left and right rails was identical from top to bottom. The lift cylinder anchors were re-torqued to specification, and the chains were re-tensioned to equal slack. The mast then operated smoothly and quietly at all heights.
