I reply, not in direct response to the tech question here, but rather to the content: Coming straight from experience and advice from the head tranny mechanic at our local ford dealer (who is also a close friend)..."NEVER EVER PULL IN OVERDRIVE with an automatic tranny!!!" The only thing worse that you could do is back your trailer up a hill or such loads. I promise you, this will eat your tranny quicker than you can see straight. I know that it means you can not go much over 65-70, but it is that or a $3K tranny.
On another note, gauges are so worth it when you are hauling and/or have any kind of mod.