the 3.55s are actually the most efficient gears as they turn the engine slower per turns of the wheels (3.55 revs of the driveshaft to one of the axle) if you are driving under 40 you should have OD off no matter what gear ratio you have in the back, while most people dont do this and it does not hurt anything if you dont, it is very helpful in the mpg department. btw i have a 02 slt+ w/ 4x4 and the 4.7, i get about 16 around town and 20-21 highway (if im nice on the highway and dont drive like a dick), it all come down to how you drive it, yes a 2wd truck would get better gas mileage than a 4x4 since it is lighter, and is not pushing the extra frictional load of the front half of the drivetrain.

no what you are saying about finding one with the 3.92 gears for city driving, the 3.92s give you a more "peppy" feel, a little quicker launch off the line but that is because it lets the engine turn at higher rpms which puts it more in the powerband, it revs much more easily, but it is NOT more efficient once you get up to cruising speed where you want to turn the lowest possible rpms
(i turn about 2k at 75)

 

would there be some reason my 4.7L AWD is only getting 17 on the highway?

 

that sounds about right for an awd model actually, my 4x4 is rated for 13 city 17 highway and i have part time 4x4, so you are already doing equal to or greater than your epa rating,(which are inflated to make the vehicle seem like it is better on gas) so you dont have much to complain about, but if you noticed a drop you could start by checking your tire air pressure, run as high as you can without creating an improper treadwear pattern. you could also do a tune up with fresh plugs gapped properly and clean the throttle body, a clean air filter, and maybe some fuel injector cleaner, but all in all the biggest thing you can do for mpgs is to keep your foot out of it, push your seat back so its a stretch to get the pedal to the floor.

also what gears do you have? if you have 3.92s your mpgs will be lower

 

ok, thanks for all the help. I just read my sticker and I do have the 3.92.

 

392's are better for more power......

 

The best D for mpg is the one that's left in the garage or driveway! LOL!

 

I have a 2002 4.7L and it gets 23mpg at 65

 

get a dakota with the 3.7 and a 5 spd manual trans. leave small tires and get a bed cover and you might get 25 mpg that or swap a cummins in the durango.

 

Well I have a V10 and get 12.75 hwy and 6 in the city.......LOL

 

Once again Hydra trumps everyone.