AC 715B steering issues

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   Recently bought a 715B (I think)  The plate also shows 715D just below the 715B.  Steering works great for a while, then starts to feel like it is slipping, then stops steering all together.  Can continuously turn steering wheel with no movement at the wheels.  Previous owner replaced the orbital valve and thinks that he had the steering cylinder rebuilt.  I have been trying to locate the priority valve.  I think it may have been removed before the previous owner purchased it.  Where should I find the priority valve on the backhoe?  Is it possible to properly operate without it since there is a separate steering pump?  Thanks

Edited by Specialized37 - 30 Jul 2025 at 6:40am

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Specialized37 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 29 Jul 2025 Location: Tennessee Points: 3	Post Options Post Reply Quote Specialized37 Report Post Thanks(0) Quote Reply Topic: AC 715B steering issues Posted: 29 Jul 2025 at 7:58pm
	Recently bought a 715B (I think) The plate also shows 715D just below the 715B. Steering works great for a while, then starts to feel like it is slipping, then stops steering all together. Can continuously turn steering wheel with no movement at the wheels. Previous owner replaced the orbital valve and thinks that he had the steering cylinder rebuilt. I have been trying to locate the priority valve. I think it may have been removed before the previous owner purchased it. Where should I find the priority valve on the backhoe? Is it possible to properly operate without it since there is a separate steering pump? Thanks Edited by Specialized37 - 30 Jul 2025 at 6:40am

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Coke-in-MN Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Afton MN Points: 41963	Post Options Post Reply Quote Coke-in-MN Report Post Thanks(0) Quote Reply Posted: Yesterday at 12:44am
	Seems my 715 B/D is having steering quirks also - when road driving machine turning when to correct travel it will make a complete revolution of the wheel in a short time . Figure it has to be leakage in the cylinder but on job one can turn wheel and lock wheels in turn position The wandering on steering has been there since I bought the machine back in 87 or 88 with 2000 hours on it . I have rebuilt all the hydraulic cylinders except the on on front axle . I have a Digmore extend a hoe on rear
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Specialized37 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 29 Jul 2025 Location: Tennessee Points: 3	Post Options Post Reply Quote Specialized37 Report Post Thanks(0) Quote Reply Posted: 16 hours 19 minutes ago at 2:36pm
	Coke, thanks for your reply. I have bought a parts manual and have been looking for a service manual with no luck. The service manuals that I do find state that they are for a 715. I'm not sure how accurate it would be. Do you know of any good sources for parts and maybe a service manual? Thanks again

DrAllis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Points: 21751	Post Options Post Reply Quote DrAllis Report Post Thanks(0) Quote Reply Posted: 11 hours 17 minutes ago at 7:38pm
	For both posters: When the steering wheels orbitrol provides oil to a simple 2-way hydraulic cylinder, the steering wheel will ALWAYS slowly turn one way or the other. I can tell you on an A-C One-Seventy farm tractor, the steering wheel rotates slowly clockwise. This steer wheel creep is NORMAL, because the displacement of the rod end of the cylinder has less cc's of oil than the other end of the cylinder. So, back and forth turning of the steer wheel constantly swaps more cc's of oil for less cc's of oil. On the original poster's problem, disconnect both hoses at the steering ram and cap/plug the end of each hose. Now, try and turn the steering wheel with the hoses plugged. I would expect you to NOT be able to turn the steering wheel, or if you can, it would be with great difficulty. If this is true, the steering cylinder must have a terrible internal leak. Over the years, I have fixed DOZENS of hydrostatic power steering tractors for "wandering" while roading. Every time the fix is a seal kit in the steering cylinder or get a new cylinder. Not once in almost 50 years have I ever replaced a steering orbitrol on an A-C machine.