Steering Circuits

Steering circuits

Hydraulic power steering is standard equipment on all tractor models. The internal hydraulic pump (2—Fig.1) pulls oil from the reservoir through a full flow suction filter installed in the outside of the multiple control valve (13). The filtered oil is pres­surized by the pump and is supplied to the priority flow divider valve in the multiple control valve. The flow divider valve directs 3 gpm (11.35 L/min.) of oil to the steering system at all engine speeds. The fluid enters the hand pump and flows through the 2150 psi (14824 kPa) relief valve. With steering wheel in neutral position, oil flows out of return port and back to the multiple control valve. If steering wheel is turned in either direction, fluid in the hand pump will be directed through the metering valve to the desired steering cylinder port. Return oil from the cylinder flows back through the hand pump and on to the multiple control valve.
Some of the steering return oil is used to operate the power shift transmission and the front drive axle clutch valve, if so equipped. The remainder of the return oil is directed to the operating spool for the pto clutch and to the transmission oil cooler. Oil from the cooler is used to supply the brake system.

Fig.1—Exploded view showing hydraulic pump, filter, multiple control valve and relative components.

Lubrication and bleeding


The tractor rear frame serves as a common reservoir for all hydraulic and lubrication operations.
The filter element (15—Fig.1) should be renewed after 20 hours, 200 hours and then every 800 hours of operation. Hydraulic fluid should be drained and new fluid installed every 800 hours of operation or once a year, whichever occurs first. Only Hy-Tran Plus fluid should be used and level should be main­tained at full mark on dipstick. Refill capacity is 36 U.S. quarts (34 L) on tractors without front drive axle and 38.6 U.S. quarts (36.5 L) on tractors with front drive axle.
Whenever hydraulic power steering lines have been discon­nected or the fluid changed, start engine and cycle power steering system from stop to stop several times to bleed air from system. Then, check and if neces­sary, add transmission fluid.
Priority flow divider


Fig.2—Exploded view of the multiple control valve assembly

Overhaul
To remove the flow divider spool (33—Fig,2) and spring (32), remove plug (30) with "0" ring (31). Clean and inspect parts. Spring (32) should have a free length of 3.253 inches (82.63 mm) and should test 29.7 lbs. (132 N) when compressed to a length of 2.017 inches (51,23 mm). Check spool (33) and spool bore in multiple control valve housing (25) for excessive wear, scoring or other damage. Spool (33) and housing (25) are a matched set and are renewed only as a new multiple control valve assembly. Lubricate spool with Hy-Tran Plus fluid, then in­stall spool, spring and plug with new "0" ring. Tight­en plug securely.
Priority flow divider test
To check the flow divider valve (33—Fig.2), first remove the pilot re­lief valve (29) and install a test pilot relief valve. Disconnect power steering supply pipe (directly below hydraulic filter). Cap the pipe and connect the inlet hose of a flowmeter to the steering supply union. Place the flowmeter outlet hose in the transmission oil fill hole and secure with wire. Move the position and draft control levers ful­ly forward to prevent hitch movement during test. Fully open load valve on flowmeter. Start and oper­ate engine at low idle speed. Turn load valve until a reading of 1000 psi (6895 kPa) is on pressure gage and record the flow. Increase the load to 1600 psi (11032 kPa) and record the flow. Fully close the load valve and record the reading on pressure gage. Then, fully open the load valve. Increase the engine speed to 2180 rpm. Re­peat the steering flow checks and maximum pressure test at the correct rpm for each model. All of the flow readings should be between 2.6 and 3.1 gpm (9.9 and 11.8 L/min.). Maximum pressure with the load valve fully closed must be 2500 to 2600 psi (17238 to 17927 kPa).
If flow or pressure readings are not correct, check for the following conditions:
Excessive wear on flow divider spool.
Faulty flow divider spring.
Faulty pilot relief valve seal rings.
Clogged filter or faulty pump.
Correct the problem and retest. Remove test pilot relief valve and using new seal rings, install original pilot relief valve. Remove flowmeter and connect steering supply line.