I'm sure someone has had this situation...

Push the o/d button to turn off, light on shifter comes on as off...and the rpms drop.
Push the button again (turning O/D on) and the rpms increase. It appears its working 180 degrees opposite of proper.

Example to clarify...going down hill at speed, push the O/D off button and as before working correctly the rpms would increase allowing the engine to aid in some braking.

That is now 180 degrees opposite. Push that button while descending and the rpms drop like it got thrown into neutral.

 

It sounds like a computer glitch. I would disconnect the battery or batteries for a few minutes and then reconnect. See if that solves your problem.

 

Sounds like the torque converter is unlocking when it drops out of overdrive.