A heavy-duty pneumatic tire forklift was nearly impossible to steer. The operator had to wrestle the steering wheel to turn right, and the truck would snap back to center violently. The shop replaced the hydraulic orbital steering valve and the steer cylinders, assuming a hydraulic restriction. The heavy steering persisted.
We jacked the front of the forklift up until the steer tires were off the ground. We disconnected the tie rods from the steer cylinders. We then tried to manually pivot the steer knuckles left and right by hand. They were locked absolutely solid.
The steer axle uses a massive center pivot pin that connects the axle beam to the forklift chassis. This pin rotates inside a bimetallic bushing. The operator had washed the forklift with a high-pressure hose, forcing water past the grease seals and into the bushing. Over the weekend, the water rusted the steel pivot pin to the bimetallic bushing, effectively welding the axle to the chassis. The hydraulic steer cylinders were trying to twist the entire axle beam, fighting the massive friction of the rust-bound pin. We used a 20-ton hydraulic press to drive the pin out, honed the bushing, and replaced the pin. The hydraulic steering system was fine; the mechanical bind was the thief stealing the steering force.
