7700 Pump Leak under pressure.

[Dandy Dave]

Just put new disks and parts in the PTO and also a new valve to actuate the PTO unit as the old one had an ear broken off of the brake band support on one side. The valve came assembled. Now the Pump in the trans is leaking oil out of the bottom in the area that feeds the PTO. I installed a new gasket and O ring as required. The PTO will also not engage when the lever is pushed forward either. I tried the new valve with compressed air before I installed it to be sure the the brake band would be adjusted properly before installation and it seemed to work fine. Thoughts anyone? The 3 point hitch works fine. Thanks in advance, Dandy Dave!

 

[Anonymous-0]

I have a 7700 and just put new seal and o ring in the pto. It leaks as bad as it did before. I am just looking for suggestions too. Good luck.

 

[RodinNS]

Pull the lift cover and look for the leak...
Just divert the pump flow to the lift cover into a hose and dump it back in the hole.
You could have a problem with the o-ring or circlip that holds the line into the PTO control valve or a hole in the line... or the bottom seal at the pump. Basically just pull the cover and stick your head in there.
I suspect that the PTO doesn't work because it's not getting any pressure at all, so if you find the leak you'll probably solve the problem.
Also... there is probably a specific procedure for setting that PTO control valve in place. It affects the alignment of the sealing rings and the brake band. I'm more familiar with 7710's than 7700's, but there is a very specific value for that slotted screw... I just forget what it is right now. It would be best to study your service manual on the subject.

Rod

 

[sotxbill]

did you replace the pto carrier or support arm with the rings in it?

 

[Dandy Dave]

My pump is leaking externally, right at the bottom where it bolts to the rearend case when it is under pressure. Looking though the parts list I see a single O ring (Same part number) listed in two different places. One where the rear end is listed, and one where the Hydraulic pump is listed. Should the pump have two O'rings and a gasket? I assumed that there was only one. I did replace the PTO line with an o'ring at the top of the line as neccesary. To get the top cover off of this Tractor means pulling the full cab (Glass and all) off. It would be difficult to run it that way with everthing disconnected. Dandy Dave!

 

[Dandy Dave]

Yes sir, A new carrier, and new rings. Dandy Dave!

 

[RodinNS]

Well... if it's leaking to the outside, definitely go after that gasket again. I'm not sure on that pump but the 10's have a rather thick seal that sits on the end of the tube where it comes through the casting and seals against the pump housing. That needs to be good and the paper gasket. That might get you going.

You shouldn't need to pull the cab if it's a factory cab tho. Mabey at most tilt it ahead AFTER you REMOVE the hood piece just in front of the glass, or you pop the windsheild...
I've had the cover off my 7710 several times and never moved the cab. On the 10 you remove the access panel in the floor and then remove the priority pack on top of the lift cover and there's just room for it to lift out. I know the 7700 has a bit different lift cover because the hydraulic systems are different to a degree, but I think it should come out without major surgery.
You do need a fork truck or skid steer to lift it. I bolt a piece of 3" channel on the top of hte cover and clamp that to the fork, lift it about an inch, then remove the load monitor link at the right rear of the cover, then keep lifting gently. It takes a bit of jerking around to get it up and out, but if you go carefully it should be fine...
Meanwhile, hope it's just the seal at the pump.

Rod

 

[Dandy Dave]

I got into it today and it was a missing O'ring. This is not even listed in the CNH online parts break down. I found one in my O'ring kit that just fit the diameter of the lower tube and reinstalled the pump. The PTO works now. The one in the parts breakdown is in about the 9 O'clock position as you face the pump under the tractor. The one not listed is in about the 7 O'clock position. and is connected to the line that feeds the duel power valve and is larger than the one listed. Thanks for the help everyone. Dandy Dave!