So when you push the ball detent in by hand the reverse lights come on. When you put the sensor in the trans it wont work and you did make sure the shift fork is sliding over to push the ball in?

You dont have any type of gasket on the sensor do you? Factory used an o-ring but the sensor was able to screw in flush to the trans case.

You have tried 2 sensors?

Next thing I am wondering is if the shift fork is moving all the way to the reverse location. You can gauge this with the shift levers to make sure it moves all the way into position. Aside from pulling the trans apart that woudl be the only way to make sure.

Terry