I will give that a shot and see what happens. Thanks for all the all the help.
Your truck is equipped with a Perkins 1004.4 engine.
It does sound like the tandem pump needs replacement. A very simple test to perform is, at a stop turn the steering wheel all the way one way and hold it there while trying to move slowly in either forward or reverse. If the truck jerks while driving then that in conjunction with your steering indicates the tandem pump is faulty and must be replaced.
The tandem pump is a "piggy back" pump and the smaller one provides pressure for the steering and boost pressure. You can buy just the small pump but it is basically the same price as buying the whole unit.
Mitsuman;
Your truck doesn't fall in the group which required steer column replacement. Now as I understand you, the travel drive is functioning, and you have turned the steering wheel first to the right steering lock, then to the left steering lock, and held it briefly also with the engine running, brakes released and the FWR and/or the REV pedals depressed and you have turned the steering wheel and steering is not functioning with truck still driving, but when the truck is stopped steering is functioning. This sounds as if this truck's tandem pump being defective. To best confirm this, it is would be advise that a measurement of boost and maximum pressure test be run.
Model H45D60003 Ser# 352j06025545 has diesel motor not sure what make.
Mitsuman;
Do you know if this 394 has had its steer column manditory replacement performed? If I had the S/N we can better detemine if it was built before 10/2006 which is the time period.
It worked fine until a week ago. hoses have not been switched or anything like that. yes no foot on accel pedal works fine. you give it gas and start moving no steering.
just a thought, has anybody previously swapped any hoses around by mistake, very unusual to have the orbital turning unless its faulty, and when you say "sitting" do you mean the acc pedel in neutral position?
Mitsuman;
Look at the steer_hydraulic pumps "load sensing and priority valve". When steering is actuated, the load sensing pressure connection's oil tank connection is blocked by the orbital, steering control valve, which causes the pressure in the load sensing line to rise. The increase in pressure causes the priority valve to make the entire volume from the steer pump available for the steering. Their location is on the inside of the steer pump (end pump) of the piggy back pump set up.
The steer wheel turns the wheels a little. when the wheels hit the stops the steer wheel still turns. steer cylinder has been repacked. the orbital valve the steer wheel has been replaced also.
Mitsuman;
Does the operator's steer wheel continue to turn the wheels while the engine is off? Also, does the wheel show resistance and continue turning after the steer axle's wheels have reached their stops?