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I have a NH 7740 SLE 16 x 16 transmission. It won't move. PTO works, three point works. Put it in gear and it will lurch like it wants to move, but doesn't. Checked all the wiring. Checked C1-C4. Throws no codes, except when I tried to recalibrate clutch. Then I get a U28. Maximum pressure reached without causing engine to draw down. Dump valve stuck open??? Any ideas??
 

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Early or late model? Does the F-N-R lever have a cable or switch?

If cable check that the cable isn't broke and that it is moving both ends freely. Goes down to the dump valve so if its stuck you are stuck in neutral basically.

The later with the switch does the same job with a switch, wires, and solenoid valve for the dump. Inspect wiring and check with a meter that the switch is functioning.

If that all checks out good get a service manual, multimeter, and hydraulic gauges and follow the testing procedure.

The transmission is fairly robust but the electrical side of things not so much and where most problems arise.
 

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Shooting from the hip as I can't find my 40 series book (must have loaned it out once upon a time), but it should go to zero. Also there is a 2nd switch on the pedal. A pedal stop switch letting the ecm know indeed the pedal is depressed.

IIRC a fault in either of those circuits would give you an E19 code.

I'll look in my 30 series book for the potentiometer values as they are the same as the 30 series I have a book for.
 

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He probably replaced the manifold gasket on the right side of the transmission Where the solenoid valves are located. The original gasket would blow out between passages since the gasket had numerous passages where a simple hole could have done the job. Just what I remember.
 
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