I have a 1973 410 John Deere Backhoe. It is new to me, so I do not have all the history. However it is having hydraulic problems. The hydraulics are slow, pump sounds like its starving for oil. I have changed both filters, with no change. Levels look good. Transmission has no issues, forward and reverse are fine. Can anyone point me in the next best direction..
Lots of possibilities, the pump is fed from the transmission on these so you may need to get a manual and take some pressure readings. Couple things I would check right off, first the pump drive, it's a cast split splined deal that was known to wear out and slip on the pump shaft: And in the pump control head there is a strainer screen that filters the control oil used to stroke the pump, I think you remove it from the bottom, make sure it's clean, and check the little needle valve on the top of the control head I think it's supposed to be backed all the way out, it's used to destroke the pump I think for cold starting but my memory is not clear on that:
I just spent a bit of time diagnosing one of these pumps on another machine. I read through the tech manual for this pump cover to cover trying to figure a problem out. The valve on top can be configured many different ways. It could have a plug in the port so you cant manually stroke it, a tee handle or 1/2" nut on top or an electric solenoid used for cold start. The tee handle/ nut style should be backed out all the way during normal operation. I found on the one I had if I turned it in and out it improved how fast the pump came in to stroke. It must have had a bit of something in it. By the sound of what you are experiencing I think there is a chance there is something wrong in the supply pressure to the pump from the transmission. In the bottom picture there is two plugs (20) Put a gauge in them. One port will be pump discharge pressure (pump stand by) and the other will be charge pressure (oil supplied to the pump from the transmission) The pump I tested had M14 test plugs in it but some had 6 orb plugs. The charge pressure should be from 50 psi to 130 psi at 2000RPM. If this pressure is low you will have to check your transmission/ filter/ oil cooler. The pump stand by pressure should be 2300-2400psi at 2000 RPM. I found the transmission filter by pass springs weak and also oil cooler by pass spring weak. Post your results and Ill try to help out. There are a couple other guys on here that know a lot about these older backhoes.