TOOL GP 4872487 - Caterpillar

Illustration 1 g03798845
(1) Steering cylinder (2) HMU (3) Steering spool (4) Gerotor (5) Priority valve (6) Steering pump (7) Hydraulic tankThe steering pump is splined into the implement pump and driven through the hydrostatic motor. The steering system uses oil flow to provide the steering movement of the machine.When the engine is started, hydraulic oil is drawn from the tank (7) by the steering pump (6). The pump sends oil to the priority valve (5). The oil flows to the spool (3) in the HMU (2). When the operator turns the steering wheel to the right, the spool (3) moves to the left (relative to the schematic). Oil flows through the HMU spool/sleeve (3), through gerotor (4), and then to the steering cylinder (1). The oil flows to the head end of the cylinder on the left side and the rod end of the cylinder on the right. The oil that returns from the steering cylinders flows through the spool (3) to the rear drain manifold and to the hydraulic tank (7).