D8n wont steer. 5TJ01570. Changing the pressure relief

Is this tractor equipped with differential steering?

If so, the Problem list below is for the possible issues.

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Problem: Machine does not steer in either direction.

Probable Cause:

1. Low charge pump pressure or flow.

2. No pilot pressure caused by:

a. Tiller not connected to pilot valve or linkage out of adjustment.

b. No supply pressure to pilot valve due to blocked hose or low pilot supply pressure.

c. Defective or improperly adjusted pilot valve.

d. Pilot valve supply pressure is low due to high leakage through ripper diverter valve solenoid valve.

3. Pump cutoff valve defective (stuck open).

4. Pump or motor failed.

5. Pump or motor loose and backed out of drive splines.

6. Parking brake not released caused by:

a. Linkage not properly adjusted.

b. Spool in brake valve stuck.

c. Internal leakage in brake valve.

I have seen the brake problem before and wanted to check that first.

Everything else is more pressure-related.

where any other repairs done recently?

Why was the pump replaced?

Then I assume it sat unused for a long time?

That leaves a chance the open systems were contaminated.

I would focus on the charge pressure next as it must be correct to supply the steering pump and pilot pressure.

Steering System Schematic (1) Steering motor. (2) Steering pump. (3) Pilot valve. (4) To ripper divirter valve. (5) Steering charge circuit filter. (6) From implement supply line. (7) Case drain implement pump. (8) Cooler. (9) Bypass and pressure control group.

The steering hydraulic system is made up of two hydraulic circuits: a high pressure, closed loop circuit that provides oil for steering the machine; and a low pressure charging circuit that provides control and makeup oil for the high pressure loop. The low pressure charging circuit also provides oil to shift the ripper diverter valve. The components of the high pressure, closed loop circuit are the steering pump and the steering motor. The components of the low pressure charging circuit are the pilot valve, the bypass and pressure control valve, the charge loop filter, and the charge loop oil cooler. The steering pump contains some components that are part of either or both the high pressure closed loop and the charging loop. The components are the charge pump, the crossover relief and makeup valves, the charge pressure relief valve, and the pressure compensator (cutoff) valve.