69chevdump,
It sounds like the 2 speed is fine, but maybe your shifting method is not allowing it to shift properly.
The shift motor winds a big spring up and loads the gear. When you relax tension on the drivetrain, it allows the spring to unwind and shove the gear into the selected position.
If you were to be in 4th under and pull the button UP to shift into hi-range, and you didn't back off on the throttle to slack the drivetrain, you could cruise forever with the spring wound and the unit just waiting to shift...you need to disengage the drivetrain momentarily for it to shift.
Play with it and we'll keep our fingers crossed.
Stuart
