2640 rockshaft stuck in up position

RoJoSmith · May 26, 2020

Went out to bush-hog yesterday. Raised rockshaft, then it would not go down. Control lever feels sloppy like linkage is disconnected. I'm sure I'll have to get in rockshaft housing. I have a service manual, the first thing it says to do is lower rockshaft. Anyone know how that might be accomplished? Is there a line or plug I can remove to bleed off pressure to allow rockshaft to drop. After it sits for a wile it does lower slightly, but as soon as I crank it up it returns to the full up position. Is there a way to access the valve from outside the rockshaft housing? Thanks for the help

Tx Jim · May 26, 2020

Is rate of drop screw(item 6) open a 1/2-1 round? One can remove plug(item 11) to let pressure out of RS cylinder.

RoJoSmith · May 31, 2020

I completely removed the ROD screw. Didn't help. Removed the rock shaft housing checked the linkage, everything looks to be as it should, however looking at linkage and moving the selector lever it doesn't look like the linkage is contacting ether valve to activate them. I manually activated the lowering valve and that allowed the lift arms to go down.

Tx Jim · Jun 1, 2020

The 2 rockshaft control valves(pressure & return) will not function correctly unless cam follower is in correct location applying pressure on linkage IE when rockshaft is positioned correctly on trans case.

I suggest to follow/perform the several RS linkage adjustment steps outlined in JD 2640 tech manual.

RoJoSmith · Jun 1, 2020

Does The cam follower fit between the two halves of the load selector link and roller? Service manual doesn't show that well.

RoJoSmith · Jun 1, 2020

Also, when working on the tractor yesterday, I was looking for the negative stop adjustment. It looks like it should be just above the draw
bar. But it looks like it might be missing. If all or part of the negative stop adjustment was missing wouldn't the hydraulic fluid drain
out? My tractor has the independent PTO

Tx Jim · Jun 1, 2020

(quoted from post at 10:49:28 06/01/20) Does The cam follower fit between the two halves of the load selector link and roller? Service manual doesn't show that well.

Yes

RoJoSmith · Jun 1, 2020

Thanks, That image is much better than what is in my service manual.

Tx Jim · Jun 1, 2020

IIRC negative stop screw is difficult to see. IPTO should have NS screw.

RoJoSmith · Jun 1, 2020

My wife sent me these photos. I'm thinking this is where the negative stop screw will be.

Tx Jim · Jun 1, 2020

I think you're thinking is correct. If you look under the bottom of trans case there's an opening so you can see the screw.

fdt860 · Jun 1, 2020

Dumb question, but did you make sure the lowering speed adjustment is not screw in all the way? That would stop it in the upper position.

RoJoSmith · Jun 10, 2020

Thanks for all the help. I did as you said making sure cam follower was in correct position. Then went through the adjustments. The load
control adjustment was off by a good bit. Thing are better but not 100%. Did not accomplish "rockshaft control lever neutral range" I think
the location where the control valve adjusting screw should be, on my tractor there is a quick couple for the front end loader. Maybe I'm
looking in the wrong location. Now that first cutting is complete I'll have time to tweek it. Many thanks Tx Jim. You have always been a
great help.

Tx Jim · Jun 10, 2020

Thanks for update. Sounds as if you're making progress. BTW you're welcome.
Jim

2640 rockshaft stuck in up position

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