955 PTO and 3PH problems

[Mechanos]

Ran into a couple of problems when I fired up my 955 project tractor tonight after swapping in a different transmission:

1. PTOs won't engage. With the PTO magnet manually bypassed (seat switch not installed yet) neither of the PTOs will engage when the PTO lever is engaged.
   
2. Rockshaft will not lower. When I cycled the rockshaft lever, the lift arms will raise, but when the lever is moved into the "down" position, the lift arms will not lower.... even with me standing on them. I thought this might not be enough force so I even tried putting a little pressure on them lift arms with a come-along. No dice... the lift arms will not lower.

Not really sure where to start looking into these problems and looking for a little "been there" advice.

Thanks.

EDIT: Ok, I'm feeling a little dumb at the moment. Went back out to the barn for a fresh look. The rate-of-drop valve was too far closed. Opened it all the way and I can easily push the lift arms down. Disregard the rockshaft issue above.

 

[Mechanos]

Well, for lack of a better plan.... I guess I will start by verifying the PTO valve control linkage adjustment. If that isn't it, I will need to pick up a few fittings so I can get a pressure reading from the PTO valve test port. For whatever reason, the PTO brake is not releasing and the PTO clutch is not engaging.

 

[Mechanos]

PTO problem is resolved..... well, actually there wasn't a problem at all. I was looking at it again to night and noticed that when I operated the PTO valve (linkage disconnected) I could hear the engine load down a little, so that told me that the valve was working. I increased engine speed and tried it again. It took a second or two for the delay valve to build pressure and then the PTO clutch engaged and the brake release and the PTO shaft began spinning.

I guess I didn't realize that the PTO would not engage at idle speed.

 

[dsmau]

That is interesting. I have never had an issue engaging the PTO on my 855 but I don't remember if I ever tried at idle. I think I might have. Perhaps yours was a little stuck from not running for a while?

 

[Mechanos]

You know.... maybe it will engage at idle. Maybe I just wasn't giving the delay valve enough time to shift pressure to the clutch/brake circuit. I will try it again tonight at idle and just give it more time to engage. When I was trying it before, I would operate the valve and when nothing happened with a couple seconds I let off of it.

 

[Mechanos]

Bad news... I definitely have PTO problems. I hooked up my 5' brush hog today to try it out. After setting up and tweaking the 3PH, I engaged the PTO and began to watch the PTO shaft on the cutter. After a second or two, it turn about 1/2 revolution and stopped. Disengaged the cutter's driveshaft and tried the PTO agian... nothing. Looks like I'll be tearing into the PTO valve after all. :mur:

 

[Mechanos]

Looked at the tractor last night to verify the PTO valve linkage was properly adjusted. I had to shorten the linkage a few turns to get the valve open all the way. This got the PTO turning again and I thought I had it...... not. Hooked up the cutter and tried it out. It would slow way down when I got to the heavy, tall grass. After one short swath, the PTO quit again and would not re-engage.

I dropped the cutter off and headed back into the barn with the tractor. Per the manual I installed a pressure gauge in the PTO Delay valve test port and ran the test procedure. At the specified RPM (3450) it is supposed to have 120psi. The first time I tired it, I was getting 110psi and the PTO shaft was spinning. On subsequent test, I couldn't get the shaft to spin anymore. One test had the pressure gauge jumping around irrattically all over the place. All the other test attempts yeilded 80psi.

The manual states to shim the valve and retest if the pressure is low. I decided that if I'm going to pull the valve out, I'm just gonig to replace all the springs and o-rings. I have the parts on order, but it will be a couple of days before they get here.

 

[Mechanos]

Pulled the Delay Relief Valve out last night. Other than the stop plug being stuck in end of the bore due to rust, it is very easy to disassemble. Couldn't see anything obviously wrong with it and had plans to rebuild it. Due to a parts ordering snafu, my parts won't be here until Monday. I was hoping to get it working this weekend and get some brush hogging done.

There are a couple of tiny little orifices that I could have been blocked or partially block. For now, I am just going to clean the valve up real good and reinstall it to see if that helps. I'm still going to rebuild the valve when the parts get here since it is so simple to pull out and replace.

 

[CARTGUY11]

Did you ever come up with anything on this? Having the same problem. Laet me know thanks.

 

[beenthere]

Welcome to TBN

You might try sending a PM (personal message) to the member and ask the question. This may be the fastest way to get a response as the thread has been stagnant for about 12 years.
Although, other 955 owners may have the answer, so lay out your question and some history or what has been happening.
Hope you get some good help.