Saving the transmission
 

Not sure if this is the right area, but I just have a quick question. Going to be towing a boat at interstate speeds. This is a one time trip about 45 miles. I frequently tow it to lake and back so I am not worried about if it can handle it, per say.

Loaded weight of boat is around 7500-8000lbs.

I have 4.10 rear end, 2wd, auto trans. Basically stock besides intake and 4" straight pipe. Also has Edge EZ which I will leave at the low setting.

Onto the question...

At interstate speeds I feel I am basically going to HAVE to leave OD on or I will be screaming down the road. It's bad enough with the 4.10s WITH the OD on.

My question is, will it hurt anything to have overdrive on at highway speeds? Is there a rule of thumb about this?

Usually, towing with the overdrive locked out at freeway speeds is not recomended,
Towing witht the overdrive locked out is usually recomended when going up mountains.
Your transmission won't like going down the freeway with the overdrive locked out.

I'm sure there are others more knowledgeable then me on this issue however I was recently having a discussion with a reputable transmission shop and he was telling me that the overdrive generates heat and recommended to keep it out of overdrive whenever you are towing