Should be electrically isolated in all but third and fourth. Off another forum:
"There is an isolator switch oc the gearshift linkage which only allows overdrive in 3rd & 4th. The switch arrangement also prevents o/d engagment in reverse gear.(sudden death for o/d unit). When down shifting into second the o/d is automatically disengaged and when upshifting back into 3rd will re engage unless the stalk switch is used."
You do NOT want to be in OD and reverse at the same time.
If you deselect the OD, does reverse work okay?