Power shift transmission – control valve


Power shift transmission consists of a three forward, one reverse mechanical gear section coupled with a four-speed, hydraulic power shift section providing twelve forward and four reverse speed selections.
Front four-speed planetary section is hydraulically controlled and changes between any of the ratios can be made while tractor is in motion without use of transmission clutch. Gear (range) speeds are selected manually and trans-mission clutch must be used.

POWER SHIFT CONTROL VALVE

Identify power shift front sequence  valve (2) and rear sequence valve (3) prior to removal as valve are not Interchangeable. Flow restrictors are located in front end rear planetary brake pressure lines (4 and 5).

Power shift control valve spool and body (8) are serviced as an assembly only. However, relief valve spring (2) and spool (3) are available separately.
To remove control valve, first remove platform or cab, if so equipped. Remove fuel tanks. Disconnect wiring harness to rear of tractor and disconnect neutral start switch wires. Remove range and power shift selector assemblies from transmission cover. Disconnect hydraulic lines and control linkage from remote valve. Remove mounting bolts and remove remote valve assembly. Remove transmission cover mounting bolts and remove wedge and shim from front of cover. Use a hoist to lift transmission cover from main frame.
Disconnect hydraulic lines from control valve (1). Mark sequence valves (2 and 3) so they can be reinstalled in their original positions, then remove both valves. Remove control valve mounting bolts and remove valve assembly.

Power shift control valve, sequence valves and related oil lines

1.Adjusting screw, 2.Spring, 3.Relief valve plunger, 4.Plug, 5.Restrictor plate, 6.Oil supply pipe, 7.Detent spring & ball, 8.Control valve body & spool, 9.Restrictors, 10.Lubrication tube, 11.Sealing washer, 12.Sequence valve front, 13."O" ring, 14.Sequence valve rear, 15.Power shift hydraulic pump, 16.Planetary brake cylinder front, 17.Planetary brake cylinder rear

To disassemble valve for inspection, remove seal wire from relief valve adjusting screw (1). Remove adjusting screw while noting number of turns required to remove screw for use in reassembly. Remove spring (2) and relief valve spool (3). Remove plug and detent spring and ball (7). Remove snap ring from valve spool, then withdraw spool from valve body. Remove test port plug (4) and restrictor plate (5). Inspect all parts for wear or scoring. Be sure control valve spool and bore are free of scoring or other damage.
Reassemble valve by reversing disassembly procedure. Lubricate all parts during reassembly.

SETTING CONTROL VALVE PRESSURE

Reinstall control valve and tighten mounting bolts to 34 N-m (25 ft.-lbs.) torque. Install front and rear sequence valves. Move control valve spool fully forward and remove plug (4) from control valve test port. Install transmission cover and remote valve assembly. Do not install power shift selector lever at this time. Remove test port plug from right side of transmission cover. Install special adapter and a 0-1000 kPa (0-150 psi) pressure gage (1) through opening in cover and into test port.
Use a remote fuel supply to operate tractor. Start engine and run to bring transmission fluid temperature to approximately 45 °C (115°F). Transmission housing must be warm to the touch. With engine running at 1500 rpm, pressure reading should be 350-560 kPa (77-81 psi) or 600-625 kPa (87-91 psi). To adjust pressure, insert a screwdriver through power shift selector opening in transmission cover and turn relief valve adjusting screw clockwise to increase pressure or counterclockwise to reduce pressure.

Stop engine and remove manifold and gage. Remove remote valve and transmission cover. Install plug in control valve test port and install a lock wire in relief valve adjusting screw to secure adjustment.
Reassemble tractor by reversing disassembly procedure while noting the following special instructions. Tighten remote valve mounting bolts to 47-57 N-m (35-40 ft.-lbs.) torque. Tighten transmission cover % inch mounting bolts to 102-122 N-m (75-90 ft.-lbs.) torque and % inch mounting bolts to 165-200 N-m (120-130 ft.-lbs.) torque. Tighten range and power shift selector housing mounting bolts to 23-28 N-m (17-20 ft.-lbs.) torque.

SEQUENCE VALVES

The sequence valves (2 and 3) control release timing of front and rear planetary clutch units. Front and rear sequence valves are mechanically identical, however, they have different pressure settings. Therefore, be sure valves are properly marked before removal so they can be reinstalled in their original positions. Front sequence valve controls release of front planetary clutch, while rear sequence valve controls release of rear planetary clutch.
To remove sequence valves, it is first necessary to remove transmission cover. Sequence valves are serviced as a complete assembly only, but valves may be disassembled for cleaning and inspection. It is recommended adjustment screw setting not be disturbed during disassembly.
All new sequence valves obtained through parts are adjusted at factory to rear sequence valve pressure setting (which is lower than front setting). If a new sequence valve is to be installed in front position, increase factory setting by turning adjusting screw clockwise two full turns.

Power shift sequence valve. Adjustment screw (11) setting should not be changed unless valve pressure is to be reset

1.Pressure line, 2.Ganket, 3.Valves body, 4."O" ring, 5.Piston, 6.Spring, 7.Sprint neat, 8.Gasket, 9.End cap, 10.Locknut, 11.Adjusting screw

Pressure setting of sequence valves can be checked and adjusted using a suitable hand pressure pump and a 0-400 kPa (0-60 psi) pressure gage. Remove hydraulic pressure line from valve, block orifice in piston with tape and reinstall pressure pipe. Connect sequence valve to hand pressure pump and pressure gage. Operate hand pump slowly and note pressure reading at point pressure makes a rapid drop indicating valve opened. Adjust screw (11) until pressure release point is 210-220 kPa (32-33 psi). If valve is to be installed in rear position, tighten jam nut to secure adjusting screw at this setting. If valve is to be installed in front position, turn screw clockwise an additional two turns and secure with jam nut. Remove tape from piston orifice, reassemble valve and install in proper position.

POWER SHIFT HYDRAULIC PUMP

The power shift hydraulic pump is mounted on lower right-hand corner of range gearbox front cover. The pump is gear driven from reverse gear of range transmission.
To remove pump, first separate power shift transmission from main frame. Remove manifold and pump mounting bolts, then remove pump assembly from rear side of housing.
Use a suitable puller to remove pump drive gear. Remove Woodruff key, then separate pump rotor assembly from pump body.

Power shift hydraulic pump

1."O" rings, 2.Bushings, 3.Idler gear, 4.Driven gear, 5.Bushing, 6."O" rings, 7.Pump body, 8.Drive gear

Inspect all parts for wear or damage. Pump rotors and bearings are serviced as a complete set. Renew all "O" rings.
When reassembling, make sure sides of bearings with oil grooves are against gears. Lubricate all parts with clean oil during assembly. Install drive gear using a new locknut and tighten nut to 73-86 N-m (54-64 ft.-lbs.) torque.
Reinstall pump and manifold using new "O" rings in oil ports. Tighten mounting bolts to 23-27 Nm (17-20 ft.-lbs.) torque.