A high-capacity sit-down counterbalance forklift was brought into the shop because the operator complained that the forks were always "crooked." No matter how many times they adjusted the side-shifter, the right fork always sat about an inch lower than the left fork when fully lowered to the ground. The warehouse assumed the forklift carriage was bent from a heavy impact, but visually, the carriage looked perfectly straight.
We put the forks on a flat, level concrete floor and measured them. Sure enough, the right fork was resting solidly on the floor, but the left fork was hovering an inch in the air. We raised the forks a few feet, pulled the mast tilt back slightly to take the load off the chains, and measured again. They were perfectly level. When we tilted them back forward, the left fork dropped.
The issue wasn't the carriage, the forks, or the side-shifter. The issue was the lift chains. A forklift mast is raised by two heavy roller chains-one on the left side, one on the right side. Over years of lifting maximum loads, these chains stretch. It is a microscopic stretch that you can't see by looking at them. However, in this case, the left chain had stretched significantly more than the right chain.
Because the forklift's carriage hangs from these chains, when the mast is tilted forward and the chains go slack, the carriage drops until the forks hit the ground. But because the left chain was longer, the left side of the carriage dropped further before hitting a stopping point (usually the chain anchor bracket), leaving the right fork hanging in the air. We put a chain tensiometer on both sides and confirmed the left chain was well past its wear elongation limit. We installed a matched pair of new chains, and the forks sat perfectly flat on the ground. It's a subtle, often-overlooked diagnostic: if a forklift's forks are out of level and the carriage isn't bent, always check the chain lengths before you start replacing expensive mast cross-members.
