350 U. Rethinking the 1 way power steering

[Paul 300 U]

Many previous posts on my 350 purchased with one way steering. I did get it working ok after a rebuild then a previously welded shaft broke. I replaced the shaft and cannot get it to work since. Turns freely both ways with tractor off the ground and not running. With front end off the ground and engine running turns great to the right but left becomes a bit difficult. When I put the front on the ground and running , turns right "ok" but won't turn left unless I pull it very hard. I always try multiple turns and let it stay completely turned in each direction to bleed air out of system.
This system essentially functions by hydraulic pressure pushing a piston backwards or forwards based on hydraulic fluid pushing on either side of the piston. At the end of the piston rod is a race that connects to gears that move the steering left or right. Fluid to the piston is via a valve in the steering column. The steering column runs through the center of the valve which has ports. Fluid moves through the ports (Left, Right, Centered) based on up and down movement of the steering column itself. I've had it apart many times. There are no broken parts. My question today is, are there other parts of the hydraulic system that could be causing the problem. Are there other valves in the hydraulic system that could be blocked. Loader hydraulics and fast hitch hydraulics work great.
Other than working on this system I don't have much mechanical experience. With the help of the forum I've been able to make several repairs to my 300 u and my cub.
Any all suggestions welcome as I'm running out of options. My concern is that even if I decided to replace the steering box, the issue might be outside the box itself.
Thanks! Paul

 

[Janicholson]

Many previous posts on my 350 purchased with one way steering. I did get it working ok after a rebuild then a previously welded shaft broke. I replaced the shaft and cannot get it to work since. Turns freely both ways with tractor off the ground and not running. With front end off the ground and engine running turns great to the right but left becomes a bit difficult. When I put the front on the ground and running , turns right "ok" but won't turn left unless I pull it very hard. I always try multiple turns and let it stay completely turned in each direction to bleed air out of system.
This system essentially functions by hydraulic pressure pushing a piston backwards or forwards based on hydraulic fluid pushing on either side of the piston. At the end of the piston rod is a race that connects to gears that move the steering left or right. Fluid to the piston is via a valve in the steering column. The steering column runs through the center of the valve which has ports. Fluid moves through the ports (Left, Right, Centered) based on up and down movement of the steering column itself. I've had it apart many times. There are no broken parts. My question today is, are there other parts of the hydraulic system that could be causing the problem. Are there other valves in the hydraulic system that could be blocked. Loader hydraulics and fast hitch hydraulics work great.
Other than working on this system I don't have much mechanical experience. With the help of the forum I've been able to make several repairs to my 300 u and my cub.
Any all suggestions welcome as I'm running out of options. My concern is that even if I decided to replace the steering box, the issue might be outside the box itself.
Thanks! Paul

350 U PS

The pressure that allows it to work in one direction is the same pressure that would work in the other direction. Therefore, the issue is local to the steering valve just under the dash sheet metal. The spool valve Part #25 must move upwards as well as downwards to direct pressure to opposite sides of the piston. If there is a component misplaced the valve could be jammed from movement (that would make steering that direction an absolute chore. The steering wheel movement will also tell a tale on this. with it shut off, turn to the right the steering wheel shaft should move downward into the upper seal where the shaft comes out. now turn left the steering shaft should come upward the same amount. This is the spool valve moving down and up. If it does not move in one way and does the other, something is jamming the movement. If the upper and lower thrust bearings are good and the spool moves fully from one end to the other I Have no more insight. Jim

 

[Paul 300 U]

350 U PS

The pressure that allows it to work in one direction is the same pressure that would work in the other direction. Therefore, the issue is local to the steering valve just under the dash sheet metal. The spool valve Part #25 must move upwards as well as downwards to direct pressure to opposite sides of the piston. If there is a component misplaced the valve could be jammed from movement (that would make steering that direction an absolute chore. The steering wheel movement will also tell a tale on this. with it shut off, turn to the right the steering wheel shaft should move downward into the upper seal where the shaft comes out. now turn left the steering shaft should come upward the same amount. This is the spool valve moving down and up. If it does not move in one way and does the other, something is jamming the movement. If the upper and lower thrust bearings are good and the spool moves fully from one end to the other I Have no more insight. Jim

Jim, I appreciate you running this through your brain once more, it helps clarify next steps. Manual shows a dial gauge that attaches to the top of the steering column and clamps to the dash to keep it steady. As you know the total amount of movement top to bottom is relatively small, about a tenth of an inch. I'll need to devise a way to measure this.
The thrust bearings, #16 were new needle bearings. Perhaps they were damaged through removal or pressure from the system not working. They look fine however. Lastly I'll have to see if their is anything holding up the valve. Considering some of the other parts looked a bit rough on the first rebuild I was happy to see how clean the valve was. No mars or scratches and I've been extremely careful handling it.
One area that's a mystery is how the valve actually senses up and down movement from the steering shaft. I'm hoping there's not wear making itso out of tolerance that the valve is not getting proper contact from the column.
Thanks again. Paul

 

[Janicholson]

Jim, I appreciate you running this through your brain once more, it helps clarify next steps. Manual shows a dial gauge that attaches to the top of the steering column and clamps to the dash to keep it steady. As you know the total amount of movement top to bottom is relatively small, about a tenth of an inch. I'll need to devise a way to measure this.
The thrust bearings, #16 were new needle bearings. Perhaps they were damaged through removal or pressure from the system not working. They look fine however. Lastly I'll have to see if their is anything holding up the valve. Considering some of the other parts looked a bit rough on the first rebuild I was happy to see how clean the valve was. No mars or scratches and I've been extremely careful handling it.
One area that's a mystery is how the valve actually senses up and down movement from the steering shaft. I'm hoping there's not wear making itso out of tolerance that the valve is not getting proper contact from the column.
Thanks again. Paul

The worm and sector pin down below are the moving force. as you turn the wheel the manual rotation of the worm climbs the sector pin and pushes the steering shaft/wheel/spool upward causing fluid flow pushing the piston powering the gears (and sector pin) in that direction. Turning the other way causes the sector pin to pull the steering wheel downward (and all those parts) flowing pressure to the other side of the piston. I do not know the fit of the sector pin to the worm tolerance, but the pin should fit the worm groove well. This can be a factor in when and how far the valve is moved. (best I have) Jim