I would be looking at the priority valve (mounted a the rear). Filter key 7 might be clogged. Key 6 adjusts steering pressure, 1/4 turn = 250psi.. There is are test ports on the back to check pressures, one is steering. Top right IIRCC. Should be between 145-218psi at 1500rpm, steering not turned, at lock 2540-2730psi.