Help! John Deere 750 3Point Hitch Wont Raise

[Deere9798]

Hi Guys, While I was out brush hogging with my John Deere 750 compact tractor, I noticed that the 3 point hitch had lowered completely down. When I tried to raise it the upper arms move about a half an inch but they don't seem to have enough power to lift the implement. Does anyone have any idea what could be the problem?

Thanks so much,
Charlie

 

[Wagtail]

Have you tried the (usually black, twist) knob under seat? It's used to adjust the rate of up/down for the 3PH.

Vibration may have loosened or 'backed-it-off'.

 

[Deere9798]

Have you tried the (usually black, twist) knob under seat? It's used to adjust the rate of up/down for the 3PH.

Vibration may have loosened or 'backed-it-off'.

Yes, I moved it to the Open position with no success. I also tried disconnecting the implement and trying to raise it. It went all the way up but extremely slowly. I did stand on the arms and it did not sink until i used the lever.

Thanks,
Charlie

 

[oldtimer 66]

Looking at the knob. Turning it CW will restrict the hydraulic flow thus slower response or movement of the 3 pt arms. Turning it CCW will increase the hydraulic flow thus faster response or movement of the 3 pt arms. There is a small valve under the seat also that has a roll pin as a arm. It is not the knob that Wagtail is referring to. I cannot remember what the small valve with the roll pin arm does. This is all from memory so I could be completely wrong. Later.

 

[Deere9798]

Looking at the knob. Turning it CW will restrict the hydraulic flow thus slower response or movement of the 3 pt arms. Turning it CCW will increase the hydraulic flow thus faster response or movement of the 3 pt arms. There is a small valve under the seat also that has a roll pin as a arm. It is not the knob that Wagtail is referring to. I cannot remember what the small valve with the roll pin arm does. This is all from memory so I could be completely wrong. Later.

Thanks Old Timer! I checked my operators manual and that valve just determines the rate of descent for the 3pt. Anymore ideas?

_Charlie

 

[Oldtink]

I'd take a look at the feed back linkage. It should fully depress the valve when you move the lever to raise the 3PH and as it nears the stop position the linkage slowly lets the plunger back out. As the rock shaft piston may leak down over time with a load the feed back linkage pushes the plunger back in to pass oil to the piston.
There are a lot of exposed pivoting parts to that feed back linkage...and they all have to work smoothly.
And that's my shot in a dimly lit memory of years ago.:laughing:

 

[Deere9798]

I'd take a look at the feed back linkage. It should fully depress the valve when you move the lever to raise the 3PH and as it nears the stop position the linkage slowly lets the plunger back out. As the rock shaft piston may leak down over time with a load the feed back linkage pushes the plunger back in to pass oil to the piston.
There are a lot of exposed pivoting parts to that feed back linkage...and they all have to work smoothly.
And that's my shot in a dimly lit memory of years ago.:laughing:

Thanks so much Oldtink!, I will definitely give that a look. Do you think that's more likely than some failed seal or pump? Also if anyone else has input I am all ears.

_Charlie

 

[Deere9798]

So I tried activating the plunger with a screw driver and it really didn't have any effect. The upper arms raised extremely slowly and I was able to stop them from raising by leaning on it. Any more ideas guys?

_Charlie

 

[Oldtink]

Well, that's above my pay grade to speculate any further...but there are two relief valves on both sides of the "stop valve" a pressure relief and a surge pressure valve. Possibly something got under a seat or a broken spring.

 

[Deere9798]

Well, that's above my pay grade to speculate any further...but there are two relief valves on both sides of the "stop valve" a pressure relief and a surge pressure valve. Possibly something got under a seat or a broken spring.

Thanks for your advice so far! Do you know of any other forum members who might be acquainted with this tractor?

Thanks again,
Charlie