I have a DP70 that had the ECU bypassed for years for the high speed solenoid and was controlled by manually switching the toggle switch to activate high. I am trying to make it shift again the way it should. I replaced the ECU and it still does the same thing. It starts in high, and will automatically switch to low gear at speed. It is working backwards! When I test voltage to the high speed solenoid, it has power, the drops out when it should be shifting to high. There is 2 diodes at the valve body that test good. What am I missing? Should voltage apply the high solenoid, or should it drop to activate? When the ECU was bypassed, putting voltage activated the solenoid fine. Is it possible that I have the wrong solenoid for the high speed? I notice the parts breakdown lists a different part number for the high speed. Sorry for the long post. Thanks for any help! S/N# T20C60961
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Just wanted to give an update. It turned out that the transmission controller was working fine. It was CORRECTLY dropping voltage to the high speed solenoid to shift to high speed as designed. Apparently over the years, someone replaced the high speed solenoid in the valve body with one that was for the low/ reverse side. Low/ reverse are the same part number, but high speed is different. Solenoids look identical, but are apparently different internally. Replaced high speed solenoid and all functions are good. Thank you to Mick at Atlantic Lift Trucks out of Baltimore Md for getting me going
i know this is a little old but, the solenoid should only have power when the trans control unit sends power to activate the solenoid. there is also a switch mounted on the column that is a two position one is for 1st gear only high speed lockout and the other turns on the ( auto ) feature by allowing the computer to send signal based on the speed sensor input. you defiantly have a wiring issue if your trans controller is new. the wire schematics are a little lacking as is the service manual on how the system functions.
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