I have solved this issue on my 5600D series.
I would drive for a couple minutes in all wheel steering mode and the alignment would be all out of whack.
I spent a ton of time testing and trouble shooting various parts of my machine to solve this problem, and finally I have fixed it.
At first I figured it was a faulty steering position sensor, so I replaced the sensor on each cylinder. No luck.
Then I tested both cylinders and found that the front cylinder was bleeding through a bit. So I went through a painful process to remove the front cylinder and rebuild it ( I put a video on youtube of easiest way to remove front cylinder) After rebuilding front cylinder, no luck, same problem.
Thats when I decided to pressure test everything in the system with an in line hydraulic pressure gauge. I tested each port going into the steering cylinders. Two front ports tested at 1400 psi. Then when I tested the back cylinder ports, found that one port was getting 1400 psi and the other port was deadheading at less than 500 psi.
This was my big aha moment. So in the back middle of the machine under the dump bed, there is a steering selector valve block. It has two valves on the outsides of the block and a pressure relief valve in the middle of the block. It also has 3 steering solanoids attached to it powed by 12 volt green and black wires. When in two wheel steer mode the fluid flows to this valve and then is directly diverted back to tank. When in 4 wheel steering mode, the valve block is actuated electrically/magnetically to move fluid to the back steering cylinder when you turn.
Because my unit deadheaded on one side of the cylinder at less than 500 psi, i figured that my pressure relief valve was jacked up. I noticed that when i unplugged the electrical plug to the relief valve, i got full psi on both side of cylinder. In the interest of saving money i was planning on replacing just the relief valve. When I called bobcat I found that to buy just the relief valve was like $350, and to replace the entire valve block with all new valves, solanoids, and a new block was only $497. Since i was not 100 % sure that it was just the relief valve, I decided to replace the entire assembly for only $150 additional cost. Boy was I glad I ordered the whole kit and caboodle. After swapping out the steering selector valve assembly, I inspected the aluminum block visually and noticed that the inside of that block was trashed. Warn down metal, and some small chunks broken off completely.
That beng said, with the new valve block in, the steering stays in line very nicely and that annoying problem is gone. Thank god.
Having gone through and spent a ton of time learning about this steering system on the toolcat, i would be happy to answer any questions if i am able to help in any way, or provide part numbers of what i replaced. Hope this is helpful to somebody as I know how frustrating this machine can be.
-Sam
