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HELP! 826 Hydro tranny trouble!

C

Centaur Nut

Member
I was cutting hay & having fun when suddenly the clutch(foot&inch valve) quit working. I had to pull the range selector to neutral to stop. I then discovered I have no reverse, but the tractor shudders when you put the selector in reverse, and when you move the selector into forward range the lever keeps creeping up until you have to pull it back to slow down. I have overhauled the clutch valve, removed & tested the reverse pressure relief valve, and overhauled the range selector valve. Any suggestions? Thanks, Rick.
 
I say you have servo cyl problems internally. Might be a broken line, or leaky cyl or just low servo pressures caused by the servo relief valve. Actually I would cap the two fittings to the lines going to control valve and see if it still acts the same. Note, you will have no foot-n-inch valve at all then either. I can understand the S-R (speed ratio) lever moving by itself if you have servo problems but don't connect that to no foot n inch control that is why I say cap the lines to isolate internal from external problems and then work from there.
 
On second thought, forget the servo bussiness and just cap those two fittings and see what happens.
 
Pete, do you mean the 2 lines coming up to the selector valve from inside the transmission, behind the left battery, and which end do I cap, transmission or selector?
 
(quoted from post at 17:14:47 05/13/11) Pete, do you mean the 2 lines coming up to the selector valve from inside the transmission, behind the left battery, and which end do I cap, transmission or selector?
Click to expand...

Cap the two lines coming out of the transmission. You will need two 1/4 inch flare fitting caps. If you can find steel caps that is best. Steel ones should be 37 1/2 ° flare which is what the tractor uses. If all you fan find are brass they may work nbut most likely they will be 45° and may fail as you can develop pressures in excess of 5000 PSI.

Capping the lines eliminates all the controls except the lever. That is a good test to see whether the problem is inside or outside the transmission housing. Make sure you have enough room around you so that you can stop by shutting off the engine if you have to.

It is kind of strange that the Foot-N-Inch valve did not stop the tractor. It's function is to control the pressure at which the high pressure relief valves open. Depressing the pedal results in both high pressure valves opening and the tractor will stop. Normally any failure results in the tractor stopping. I would lean toward servo problems since the pump servo controls both forward and reverse functions. The motor servo only controls the speed in the upper forward range.
 
With the lines capped how should it act? Will I have any range control or will it just be wide open or stopped? If it is the pump servo can it be reached without breaking the tractor in half? The service manual I have mentions a clogged orifice in the pump servo as a possible cause, but not all my symptoms match my book.
In any case before I try anything I've got to move the tractor. I had the feeling I was making a mistake when I nosed it into the shop, in front of my bass boat, with reverse not working!
 
Since you have it in the shop you can raise the rear until the wheels are off the ground and do the troubleshooting in there. Be sure it is securely supported and that the wheels are free to turn.

With the lines capped off the the tractor should operate as normal with the exception of the Foot-N-inch valve being inoperative. The S-R lever will still control the servos but the side to side movement will no longer put the hydro in neutral if it is in center of the cross slot. If the tractor works with the lines capped the problem is in the exterior controls. If you still have problems the trouble is internal.
 
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