My truck is a '06 2500 with a manual transmission. Fuel mileage is quite a bit less than some friends with autos. They run a couple hundred RPM less at highway speed than mine.
Why does my truck run at a higher RPM for the same speed? Is it the rear end? If so can that be changed? What about aftermarket overdrives?
I bought the truck with the manual thinking it would be better for hauling a heavy trailer. As it turns out an auto probably would have been better.

Here are a couple shots just for the heck of it.

 

dude Can I use that trailer I have a sail boat to move and no trailer.lol
with what you are describing that you have a bigger gear ratio in the axles then the auto trans My friend Eli has a manual trans and at 65 he is at 2000 rpm I have a auto I am at 65 mph at 2300-2400 rpm
well what trans do you have and what axle gear ratio do you have? that is the big question. did you buy it new? used? if used they may have ordered it with a pulling gear and your need a highway gear

 

Not sure which rear end it has. Is that in the VIN or tagged on the rear end?

 

the rear end is tagged if its still there.

 

Hey brother, send me the last 9 of your VIN and I'll see what you have.

 

If you have an '06 manual transmission there is only one gear ratio available 3.73:1. What kind of mileage are you getting and doing what kind of driving? My truck if kept at 65 or below will get 18 -20 mpg empty. We run higher rpm's then the auto trucks with the same rear end gears because our overdrive is lower (.79:1) then the auto. But as a result we pull better in overdrive. They have since come out with 3.42:1 gears for the 3rd gen trucks but you will never pay them off in fuel economy unless you put a lot of miles on the truck.

 

Guess I learned something new I though with dodge like other brands they offer different gear ratios. Even if you special order it?

 

With the 6.7 and manual trans I believe you can get 3.42 or 3.73, and with the auto from '03 up you can 3.73 or 4.10. But the '05 - '07 5.9 with manual only came with 3.73.