302a rockshaft question

[moo2613]

I am trying to use my 1,500# 3-point brush hog. Which setting do I want on the selector? I would think I want "D" for depth control. Problem is that in the "D" position, the arms will not lower no matter where the control lever is positioned. In either "LD" or "L", it is constantly trying to move up or down on its own. Also, the arms lower immediately after shutting the tractor off, I assume they should stay in the positionat time of shut down.

 

[Tx Jim]

You're correct all 3 pt functions except plowing should be performed in "D". 3 pt not operating in " is an indication that L/D mechanism isn't set correctly or some part possibly the cam(parts key 17) or spring(parts key 18) has failed. Immediate settling of 3 pt when engine is shut off is a indication of leaking seals either rockshaft control &/or RS piston. Either way RS housing will need to be removed from tractor.

 

[moo2613]

Is this a major project? In the tech manual, it looks like about 12 bolts. Does it pick straight off? Are there internal parts that can fall into the transmission?

 

[Tx Jim]

Yes RS housing picks straight up with no parts to fall off. Be sure and replace quad ring on RH side before reattaching RS housing to trans case

 

[moo2613]

Thank you. After a few hours of use today, I was able to now for awhile, but the side of the transmission got so hot that it would burn my hand at the slightest touch. Could there be a bad relief valve?

 

[Tx Jim]

Excessive heat on a JD closed center hyd system is normally a high pressure internal leak or very dirty hyd oil cooler. Check each hyd component with a laser thermometer to determine if a hyd function is causing the heating problem.

 

[Tx Jim]

Technically there are not many high pressure relief valves associated with factory JD CC hyd systems. Most aftermarket hyd valves with built in relief valves one needs to adjust relief valves to or above system pressure of 2250 psi.

 

[moo2613]

I'm going to guess it is an internal leak. I noticed that the bucket operation was sometimes very slow with the brush hog on the tractor. Also, when I raise the bucket with the brush hog raised all the way up, the brush hog will drift down until I stop raising the bucket.

I am going to try and finish mowing my field this week (slow process because I have to continually adjust mower height) and then work on pulling the RS cover off. I suspect I will find a bad spring or seal in there. I am somewhat controlled by weather on this since I have to work on it outside. How heavy should I expect the RS cover to be? Will I need a lift?

 

[Tx Jim]

I think you will need assistance(lift) to R&R RS housing

 

[moo2613]

Ok, I have finally pulled off the RS cover and got it on the work bench, yes another set of muscles would have been helpful.... At any rate I do not see any broken springs, but the "cam spring" seems weak to me, but not sure how strong it should be. What I did see is that the Load Selector Lever had a bend to it and it was not installed through both sides of the Selector Link and Roller. In the lower picture, I had already bent it back around enough to get it in both sides of the Selector Link. Also, one of the clips that hold the Selector Lever tight to the roller is missing allowing the split to open more than it should.

Also, there are 2 valves. In the upper picture, the bottom valve is the Discharge Valve. When I move the load selector lever to its different settings, there is only 1 instance that the cam barely presses against the discharge valve while the pressure valve gets firmly pressed as the selector lever is being moved. There is also a problem with the selector lever getting stuck (while in the "D" setting) on top of the rockshaft cam and not allowing the load selector lever to move while the depth control lever is in either the lowest or highest position (I don't remember which right now, but I think it was the lowest) you can see in the picture that the ends of the selector link has wear on them. I guess I need some help here, where do I start? I have not removed the valve assembly from the RS housing as of yet.

 

[Tx Jim]

Here's the spec's on the spring in question(parts key 18). I agree L/D linkage appears worn on ends & distorted.

 

[Tx Jim]

OOPS I gave spec's on wrong spring.. Let me try again.

 

[moo2613]

Any thoughts on the valve situation?

 

[Tx Jim]

Any operation other than plowing with a 3 pt plow should be performed in "D". Have you tried adjusting negative stop screw(parts key 7 in 1st photo)?

 

[moo2613]

No, I have not. With all of my other symptoms (all hydraulic areas getting very hot, tractor not moving forward when it is started, implement dropping when bucket is moved, when placed in "D" rockshaft arms go all the way up and can't be lowered, etc.) I believe there is an issue with the rockshaft hydraulic system. Another thought is that the Thermal Relief Valve spring is bad. Since I can't seem to make the discharge valve operate, I think something is out of adjustment, but I don't know what to look for.

 

[Tx Jim]

You go through ALL the L/D adjustments listed in a JD utility tractor tech manual