Emergency Steering Function

TM 10-3930-673-34

TR00480

and goes to steer select valve (2). Steer select valve (2) ports oil flow to steering cylinders (3) according to the

selected steering condition (two-wheel, four-wheel, or crab). If two-wheel steering has been selected, only the

two front steering cylinders (3) are supplied. If four-wheel steering or crab steering has been selected, all four

steering cylinders are supplied.

c. Emergency Steering Function. Emergency steering pump (6) is powered by an electric motor and can

supply a flow of oil to the steering system independently of the main hydraulic system. If main steering

hydraulic pressure is lost or drops below a level of 75 psi (517.13 kPa), pressure switch (7) will close and

complete a circuit to energize the emergency steering pump motor. Emergency steering pump flow bypasses

priority valve (8) and goes directly to the inlet port of steering valve (1). A 1500 psi (10343 kPa) relief

valve (11) is used to protect the emergency steering pump (6) and other circuit components against

overpressure.

12-2