A reach truck was brought into the shop because it had lost all traction. The operator would press the accelerator, the drive motor would whine, but the truck would barely move, especially on a slight incline. The shop assumed the drive motor or the traction controller had failed.
We drove the truck into the aisle and applied the brakes hard. The truck stopped, but we heard a horrible grinding sound from the front. We jacked the drive axle up and tried to spin the tire by hand. It was locked up tight, but the motor was fine.
We looked at the lift chains on the mast. The operator had been complaining about the carriage being "loose," so a mechanic had cranked the chain adjustment turnbuckles down incredibly tight to remove the slack. The mast is mounted to the drive axle housing. By over-tensioning the chains, the mechanic was essentially pulling the entire mast and carriage assembly downward with thousands of pounds of force. This upward reactive force was literally picking the front drive axle up off the ground, transferring the truck's weight to the rigid center load wheels. The drive tire was barely touching the concrete, and when it did touch under load, the extreme downward pressure on the load wheels was causing the drive tire to bind and skip. We slackened the chains to the manual's specified 1/2 inch of deflection, the drive tire sat flat on the floor, and the truck drove perfectly.
