I do have the tow/haul. I'm guessing turning tow/hual on, automatically turns off the overdrive? OD off and tow haul are on the end of the auto tranny shifter. Push once, OD off...push twice tow/haul on.

I installed a brake control as soon as I got it.

I'm gonna love the mileage? Yeah, I'm guessing around 8mpg with a 26 gallon tank...It's gonna take forever to get anywhere.

 

As far as I know Tow/Haul turns off OD and locks out 5th gear to maximize torque at the lower gears.

If you're gonna be pulling about 7000 lb then yes your mileage will probably be about 8 - 10 mpg.

 

The OP has an older 2500 that does not have the tow/haul option.
Tow haul raises the part throttle 2-3, 3-4 shift points and locks out 5th.

 

Thanks everyone for you input. I guess I need to get over the fear of putting some RPM's on the V8. I'll let you know how the trip turns out.

 

The Hemi actually has a "sweet spot" between 2200-2600 rpm, I get better gas mileage at 2200 rpms then when cruising at 1800 rpm.
The engine can take sustained 2500 rpms with NO issue at all. Put the load of what you're towing on the engine, get it off the tranny, it's your Achille's Heel...

 

with my 4.56's I disable the O/D gears so I cruise at 60 ish mph at like 2800mph and the truck loves it

 

I just got back from a 350 mile tow with about 7000 lbs behind the truck. I ran up all the hills between 3000-4000 rpms and it was plenty of power. I would have to back off a bit actually to keep the speed right on. And, the stock coolant temp gauge barely even moved. I averaged about 9.5 mpg's which i was pretty happy with, and it never bogged or anything on the hills.

 

Thats good to hear. I just got back this weekend from a trip in Northern New Mexico. My truck DEFINATELY had some issues on the hills. I wasn't that surprised though, typical half ton stuff but at some points I was barely making ground at 35mph.

I'm going to add up, as close as possible all the weight that I'm towing.

 

The Hemi engine, in it's stock form, is not a real efficient tower. In fact, it's really not well suited to be a truck engine, at least not for a heavy truck, like the 2500s or 1500 QC 4x4s. It's actually more suited for the V8 muscle car segment. Don't get me wrong, it's a great engine and I love my truck, but it LOVES mid to high rpm operation and this is where it shines!

If you compare specs, the top end HP exceeds that of the venerable old LA 5.9L engine it replaced by 100+ HP, but Torque numbers are about the same. Not really good advancement in that area, considering the LA's came out in the late '60s.

Of course, it can be modded to be a very efficient tow vehicle. The power is there, just not in the right place out of the factory. Gears would be a big plus, because they allow you to get the rpms up into that higher "sweet spot" much faster. There are also cams available that along with the right custom tune, put a lot of the engines power way down low in the curve, making it a really good tower. The right grind on a cam combined with a tune designed for it can increase torque by upwards of 75 ft/lbs, and hit down low in the rpm range without any other real modifications. Start talking heads, etc. and the numbers start to look almost diesel-like.

Of course, none of this comes cheap. If you want that kind of a tow vehicle, it's probably more economical to buy a CTD...

 

There was a study by SAE years back on efficency and wear of gasoline engines. I payed attention to the numbers for the small block chevy, but I would assume since displacement of the HEMI is close to a 350 chev, it would be a similar comparision. (I'm not interested in comparing bore, stroke, journal dia's, etc and speculating what that means)

Basically the study's results shown that about 2600 rpm is the cutoff point that a SBC will start to show increased wear over sustained time at that rpm. So, you should see the same amount of wear in a "stock" SBC from say 1800 to 2600 rpm, and increased wear above 2600. Unfortunatey, I don't recall any other details. The additional amount of wear you will see is proportional to RPM. i.e: you're going to get a lot shorter engine life if you turn 5000 rpm on the freeway vs 2600. Let your intuition be your guide.

My guess is that you are not hurting your engine to turn in the upper 2000 range for long durations assuming things like engine and oil temp don't increase significantly.