John Deere M Rockshaft Not Working

wnettles · Sep 24, 2017

I have a 1947 John Deere M tractor (my grandfather's) and the rockshaft will not move when I pull up on the Touch O Matic control lever. It worked for the last 70 years or so, but, now it will not lift.

Plenty of oil in the sump, good pressure out of the pump, but, no lift. Took the front case cover off of the control valve housing and inspected all the linkages for a missing pin, but, everything is in place.

Manually worked to rockshaft arms up and down and the control valve is getting the mechanical feedback signal via the rod from the rockshaft. What could be the problem and where to look next?

Never had to take one of these apart..... Guess there is first time for everything. Any suggestions or tribal knowledge would be much appreciated.

Brendon-KS · Sep 25, 2017

You mentioned that it has "good pressure out of the pump". Where and under what conditions was this measured? On an open center system like this there should be essentially no pressure developed anywhere until the valve is moved to port the oil to the lift cylinder. Otherwise the oil is in full by-pass and is being routed back to tank. If pressure builds up to relief (a little over 1000 psi) between the pump and valve when you move the lever to lift and the rockshaft doesn't go up there would have to be something preventing the oil from getting from the valve to the piston. If pressure isn't actually being developed the problem could be the relief valve or the pump itself.

James Howell · Sep 25, 2017

"[b:654c4848f0][i:654c4848f0]<font color="#6699ff">What could be the problem and where to look next?[/i:654c4848f0][/b:654c4848f0]</font>"

Agree with [b:654c4848f0]Brendon-KS[/b:654c4848f0] that "[i:654c4848f0]the problem could be the relief valve[/i:654c4848f0]".

Take a look at the [b:654c4848f0]TOUCH-O-MATIC CHECK VALVE HOUSING ASSEMBLY[/b:654c4848f0] diagram below.

Note the Relief Valve (Key 9).

Also note the Lock Screw (Key 6), Adjusting Screw (Key 4), and Spring (Key 7),

Take a look at the [b:654c4848f0]Touch-O-Matic Relief Valve Operation[/b:654c4848f0] illustration below.

Note the relief valve 19 is open open allowing oil to return to the reservoir.

The relief valve must be closed in order for the drawbar arms to raise.

You might consider reviewing the [b:654c4848f0]Adjust Pressure of Touch-O-Matic System[/b:654c4848f0] topic on page 180-15-13 in the service manual.

Removing the lock screw and turning the adjusting screw in (clockwise) will tighten the spring tension on the relief valve, but please read the above mentioned topic first.

Hope this helps.

John Deere M Rockshaft Not Working

wnettles

New User

Brendon-KS

Well-known Member

James Howell

Well-known Member

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