[Johnnyboy]

Ht740 is not an electronic transmission. It shifts either by mechanical means, either cable and manual shifter from cockpit or Bennett air shifter which just shifts the mechanical lever at the transmission. It you can confirm it is shifting to forward gears, probably transmission related. There is a modulator on the side with an air line, I could see it going bad allowing to much air pressure into the trans blowing fluid out of it, if it’s not that, then may need trans repair.

Modulator: WM775B