Hydraulics

A forklift runs steering and lift/tilt from one pump and one tank. A flow control valve on the pump gives steering priority, passing it a fixed flow first and sending only the surplus to lift and tilt — which is why lift slows when you steer. Each circuit has its own relief valve in a different place, and adjusting the wrong one is the most common diagnostic mistake on these systems.

A tilt cylinder is a double-acting hydraulic cylinder that tilts the mast. Oil behind the piston pushes the rod out and tilts the mast forward; oil in front of the piston pulls the rod back and tilts it backward. The number and design of the parts differ between trucks, but the operation is the same, and most repairs come down to renewing seals.