3-Point Hitch Ford 6640 3pt hitch problem

[Jackfr]

Anyone have any Ideas my 1991 6640SL won't lift its 3pt hitch it doesn't move at all. Was working fine then when I went to use it nothing. But all my live hydraulics pto power steering front load ect all work fine anyone have any ideas

 

[Soundguy]

Have any selector valves on that thing.. or perhaps draft control that my be on instead of position control?

soundguy

 

[RickB]

Anyone have any Ideas my 1991 6640SL won't lift its 3pt hitch it doesn't move at all. Was working fine then when I went to use it nothing. But all my live hydraulics pto power steering front load ect all work fine anyone have any ideas

You need to flow test the remotes. Your tractor has a dual pump system. The rear pump is the exclusive source for oil to the hitch. The engine driven pump supplies oil to the remotes. If there is no hitch demand, the oil from the rear pump is combined with the flow from the engine driven pump to supply the remotes. If you have no hitch and 8 GPM at the rear remotes at free flow, the rear pump is most likely at fault. There is a whole laundry list of tests and possible faults that should be examined prior to spending dollar one on parts.

 

[Jackfr]

Tried Selector in draft and position no difference unless there is an internal problem with the linkage. The external linkage all looks fine and it feels the same as always.
How could the pump be bad if it was working fine when I shut it down no problems with the hitch just wouldn't work when I started it the next morning?? How do I do a flow test without a flow meter, pump oil into buckets? Is there anything else I can test first? I have pressure guages.

Jack

 

[RickB]

Tried Selector in draft and position no difference unless there is an internal problem with the linkage. The external linkage all looks fine and it feels the same as always.
How could the pump be bad if it was working fine when I shut it down no problems with the hitch just wouldn't work when I started it the next morning?? How do I do a flow test without a flow meter, pump oil into buckets? Is there anything else I can test first? I have pressure guages.

Jack

I didn't say the pump was bad. I said 'most likely'. This hydraulic system is more complex than most. Troubleshooting hitch problems without a factory service manual and proper test equipment is probably not going to be successful. Not having the right stuff doesn't mean you can get by without it.
If the hitch isn't working, the flow from the rear pump isn't reaching the lift cylinder. It's a matter of figuring out why. If the tractor has a trailer brake valve, that is part of the flow chart.
You can use a bucket for a flow meter IF you can control the mess.

 

[Jackfr]

The PTO is working fine thats why I thought the internal pump should be ok doesn't the PTO clutch pack work hydraulically like my F5000? I have complete factory service and parts manual and some pressure guages I started reading section on hydraulics. I'm sure I'll figure it out I was just hoping there was some easy fast fix that someone knew. such as the fix to my hydraulics in my TC45DA when the plug loosened and came out of the return in the loader spool valve. Someone here told me where to look and it was fixed in 20 minutes. If you have any other ideas I would greatly appreciate them as I'm not really looking forward to getting into this. Do you know if Ill have to remove the cab to remove the hitch cover, if I have to rebuild the hitch piston or is there enough room to lift it and slide it out over the internal stuff. I know its heavy but that would save a lot of time.

 

[Soundguy]

The PTO is working fine thats why I thought the internal pump should be ok doesn't the PTO clutch pack work hydraulically like my F5000? .

I think rick said the rear pump was exclusively for the hitch.. while the other pump supplied the other things.. if that is so... then the pto pack is probably getting oil from the other pump.

Rick's a sharp cookie on these big fords and NH's.. he's helped many of us out here.

soundguy

 

[RickB]

The PTO is working fine thats why I thought the internal pump should be ok doesn't the PTO clutch pack work hydraulically like my F5000? I have complete factory service and parts manual and some pressure guages I started reading section on hydraulics. I'm sure I'll figure it out I was just hoping there was some easy fast fix that someone knew. such as the fix to my hydraulics in my TC45DA when the plug loosened and came out of the return in the loader spool valve. Someone here told me where to look and it was fixed in 20 minutes. If you have any other ideas I would greatly appreciate them as I'm not really looking forward to getting into this. Do you know if Ill have to remove the cab to remove the hitch cover, if I have to rebuild the hitch piston or is there enough room to lift it and slide it out over the internal stuff. I know its heavy but that would save a lot of time.

The PTO, Dual Power (if equipped), MFD clutch and difflock are supplied by a second section of the rear pump. If you have PTO, all that verifies is that the rear pump shafts are turning; no proof that the main section is pumping oil. Quick and easy fixes for these two pump systems are few and far between. You may need to isolate the flow from the rear pump. Unless the hitch lifts and settles under load, your piston seal is OK, although you may have to pull the hitch cover for other reasons. You should ber able to get the hitch cover out without pulling the cab.

It may have been me posting about the TC loader valve; I have mentioned that fix here a couple times. I don't have any magic cures this time, though.

 

[Jackfr]

Thanks Rick

Do you know if the plug on top of the pump for the trailer brake option is a pipe thread or oring type? The service book says if I use Fords adapters I can test pressure of main High pressure pump at this location with a 6000 psi pressure guage which I have. If pressure stays between 2550-2650 psi at 2100 rpm and then 1200 rpm then main pump is ok. Then next place to look probably is the Priority valve pack on top of the cover. My other option is to invest in a flow meter and try your original suggestion. Any other thoughts would be greatly appreciated.

Jack

This tractor has no Trailer brake option and no ASC Valve option (that I can find).

 

[RickB]

Thanks Rick

Do you know if the plug on top of the pump for the trailer brake option is a pipe thread or oring type? The service book says if I use Fords adapters I can test pressure of main High pressure pump at this location with a 6000 psi pressure guage which I have. If pressure stays between 2550-2650 psi at 2100 rpm and then 1200 rpm then main pump is ok. Then next place to look probably is the Priority valve pack on top of the cover. My other option is to invest in a flow meter and try your original suggestion. Any other thoughts would be greatly appreciated.

Jack

This tractor has no Trailer brake option and no ASC Valve option (that I can find).

NH's online parts deal indicates that all the external plugs on the pump cover are metric straight thread. Tapered pipe threads are pretty much non-existant on this tractor except for some of the housing drains. Good luck.