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Discussion Starter #1
Hi Group.
Looking for some information on why my 3 point hitch is acting up. I've got a JD 750 four wheel drive and after being used for about 45 minutes the hitch will lower and will not rise back up until the tractor has a chance to rest (cool down?). I don't know much about the workings of the hydraulics on the old girl, but I have cleaned the screen/filter and replaced the old fluid. Sure hope somebody can give me a few suggestions as to what might be wrong.
Thanks in advance,
John
 

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So when this happens, you can raise and lower the 3-pt control lever, and it just doesn’t respond or anything? it just stays down? Do you hear any whining, cavitation, or other noise from the hydraulic system?
 

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Discussion Starter #3
Lever will move freely up and down. No whine or strain on engine. Everything seems normal other than the hitch won't lift. And even after awhile when it will rise it's for a much shorter time before it happens again.
 

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Check your hydraulic pressure when cold and hot. The factory test spec is 2030 PSI +/- ~5%. Check for a hydraulic suction hose that's collapsing when hot. There's a short length of hose at the hydraulic filter housing.

750 Hydraulic Filter.jpg

If pressure tests OK when cold and there's no appreciable reduction in pressure at operating temperature then you'll most likely have to remove the 3PH rockshaft housing and reseal the lift piston.

750 rockshaft housing.jpg

If hydraulic pressure is too low cold & hot and the fluid, suction strainer and filters are known good then look for a worn hydraulic pump.

750 Hydraulic Pump.gif

If you don't have one you can pick up a hydraulic test gauge here: Ken's Bolt on Grab Hooks <<Hydraulics>>

It's not a very big job to replace the hydraulic pump or remove and reseal the rockshaft lift piston.
 

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Discussion Starter #5
Thanks Superglidesport

Thanks for all of the great information. Really appreciate all the time you spent looking into this for me. I may have to find someone with a little more mechanical ability than myself to help out. But there are always guys around looking to help out.
Thanks again! :):bigthumb:
 

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Discussion Starter #6
Update on 3 point hitch problem.

A small update on the hitch problem that I hope might narrow it down a bit. Used the 750 today, knowing at some point I was going to see the same problem again of not being able to raise the hitch after some period of time. The problem did not disappoint....after about 45 minutes to an hour it started to lift sporadically and I noticed a small strain on the engine and when you pulled up on the lever it would spring back to the near fully down position by itself. :banghead:
 
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