My dad and I got into a discussion about how to drive on the interstate with my truck. He owned one similar to mine. Mine is a '98 5.9L 4x4 QC with the 46RE and the truck just turned over 107,000 miles.

When he used to drive on the interstate, he drove 80 in a 75 or so but he would slow down like 18-wheelers do when going up hills. I'm talking 50-55 and holding up traffic while doing so just to avoid passing gear or otherwise taking it out of OD.

On my last interstate trip, I set the cruise on 75 in OD and left it there, hills or no hills unless it started wanting to hit passing gear frequently. Every now and then I would turn OD off before going up steep hills or when facing a stiff headwind. He thinksit is horrible for the truck to do that and I should just slow down and avoid hitting passing gear or taking it out of OD.

Is hitting passing gear up hills or taking it out of OD to maintain the speed limit hard on our trannies? The way I see it, this truck is not an 18-wheeler and it damn sure shouldn't perform like one up hills.[:@]

 

Hitting passing gear to go up hills or pass someone should be fine. That's what it was made for. But if you have to turn off overdrive to maintain the speed limit, you need to slow the heck down.

 

18-wheelers slow down because they are running out of momentum climbing hills and are downshifting for optimum hill climbing. Trust me, truckers (within reason) try to get as much speed on down-grades as possible to carry the rig up the next grade as far as possible before gravity takes over.

It boggles my mind to wonder why your dad thinks truckers slow down. His actions are actually detrimental to his fuel mileage.

 

These dodges are probably the biggest ****** goin down the highway with 3.55 gears

Before I hit a hill i usually hit the O/D off button, so its a nice easy shift, not a harsh one that would happen if you hit the button half way up the hill

I hate driving my truck down the highway, its horrible especially in PA, which has alot of steep hills and ****ty highways

 

It take a lot more power to drive up a hill because now your fighting gravity more as well.
Trying to maintain a constant speed even by downshifting is still going to use more gas.
I personally downshift and reduce speed when going up steep hills. I can always make up the lost time on the down hill side if I need to.

Leaving it in OD causes more stress and load on the engine at any speed going uphill.

 

Oops, sorry I didn't say it before but I don't have to take it out of OD up hills. If I leave it in OD with the cruise control on, it will downshift by itself and run up to 3,500 RPM or so to get back up to the set speed before shifting back into OD again.

I simply chose to take it out of OD before heading up a steep hill because of the brainwashing my dad gave me about passing gear being death for transmissions. Another thing I found interesting was that if I manually took it out of OD myself and still left the cruise control on, it would run at about 3,000 RPM instead of the 3,500 RPM I mentioned above.

 

LOL, that is what I used to have to do in my little Acclaim too. I would see a big hill coming up so I would floor it to get as much momentum as I could for the upcoming hill. 100 HP + 3 gears +3,500 pounds = headaches on the highway.

Anyway, what I was trying to say is that my dad slows down like the truckers do not because he HAS to like they do, but because he doesn't want to hit passing gear. He thinks he is saving fuel and being easy on his truck by slowing down like they do instead of maintaining his "flat surface" speed. Sorry for the confusion. He realizes that 18-wheelers are loaded down and they simply don't have the power to be able to maintain 75 MPH up steep hills.

 

The torque converter will lock up in 3rd gear if you push the OD off button.
It wont lock if the trans down shifts by it's self. That the reason for the lower RPM

 

Bingo! That is exactly what I was doing and thinking. I would take it out of OD going downhill just before I started up a big hill. It seemed to be a hell of a lot smoother than when I left it alone in OD with the cruise on. Those downshifts seem to be harder. Maybe I do need those 4.10 gears. I've got the 265/75/16 tires.

 

Oh, okay. Thanks. So I SHOULD take it out of OD up hills then? I got rid of that Acclaim because it only had 3 gears and i had no choice but to "18-wheeler" it up hills. Now that I have this Ram and the ability to maintain speed up hills, I want to do it. I just want to do it in a way that is the least harsh on the tranny.

BTW, I was having these up-hillissues bone stock. Now I have a Summit Racing CAI, 180* t-stat, and the Hypertech PP III which finally calibrated the speedometer correctly. By that, I mean that the previous owner went from 245/75/16 to 265/75/16 tires without calibrating the speedometer. Now that I have done these things (new cat-back goes on this weekend) hopefully it will be easier to maintain speed on the interstate.