Husqvarna PT26D Workshop Manual page 56

Four-wheel drive without diff lock.
Circuit diagram four-wheel drive without diff lock
Four-wheel drive means driving at low speeds. Front and rear wheel circuits are connected in parallel. The
hydraulic pump's flow is distributed both to the front wheel circuit and the rear wheel circuit, at which the
wheel motors run on lower revs than during two-wheel drive.
When driving in one direction, the hydraulic oil flows out via port A to the valve block for transmission and on
through he flow distributor (f). The valve (3) is open and connected in parallel with the flow distributor, so the
chokes in the flow distributor do not have any function. The flow distributor thus supplies even pressure on both
wheel pairs. The hydraulic oil then flows through the wheel motors and back to the hydraulic pump for the drive
system's port B. A certain amount flows through a flushing valve (10), which lets 10% of the oil flow back to the
tank via the oil cooler (12). The flushing valve only changes oil which is on its way back to the hydraulic pump.
The gate valve in the flushing valve detects the pressure from the axial piston pump's A and B side and directs
the return oil to the pressure limiting valve, which opens at 1.5MPa (15 bar). The pressure 1.5 MPa (15 bar) is
needed to ensure that wheel motor circuit is filled.The return oil then flows to the tank via the radiator.
DESIGN AND FUNCTION
F=Front axle
R=Rear axle
F=Flow distributor
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