I have 2004 CTD rig with the 48re tranny. I tow a 31' trailer that weighs about 9000 lbs. My question is the TOW/HAUL mode and when to use it? From what I can tell on the 2004's the 4th gear or overdrive is locked out in the TOW/HAUL MODE. Will I hurt the tranny running down the road in fourth gear on a flat road at 65 plus mph?

 

You will have no problem leaving tow/haul OFF while cruising down the highway. In fact, you will want it to be in OD otherwise your RPMs will be uncomfortably high. Try going down the highway with tow/haul on. The big thing you have to look out for is the tranny hunting back/forth between 3rd and OD as this produces a lot of heat.

I just started using tow/haul in the city and my tranny temp stays lower longer and my mileage has stayed the same. As soon as I get between 40 and 50 I'll take tow/haul off.

 

I do the same as handy....I get on the freeway while towing I take it off as long as it dosent hunt for gears