I have an 01 2500 ctd automatic Trans, While pulling my car and trailer on the highway my rpm's are about 1800 at 65 mph. Which seem fine but the problem I have is when I hit a slight upward slpoe the truck starts to slow and the only way to recover is hit the little OD Off button then the rpm's crank up to about 2800 Rpm's at about 60 mph does this sound right.

 

sounds like youve got 3.54 gears. . .yup.

 

So this sounds normal

 

dont tow with over drive on!! always keep it on O/D off when towing. it says in the manual and i know poeple who used to tow with it on and there trannys didnt last very long.

 

I don't see why it would hurt to tow in O/D as long as isn't going back and fourth. I could be wrong. That is why I bought a 6 speed

 

I tow with my OD on all of the time. If I go up hill and the tranny seems to hunt a little, I'll take the OD off till I get to the other side. So far, so good.

 

It wouldn't make any sense to keep your OD off the whole time you're towing a trailer. Then your RPM would stay at 2,800 and your MPG would really suck. I would say keep it in OD until you hit those steep hills.