the mileage data I recorded with my 2006 2500HD, 6.0L 4L80E seems to confirm that. 20mpg 100% highwaydriving, imperial gallon.

 

as transmissions get 'larger' (more gears/range) the final drive ratio becomes less important.

even with a higher gear ratio, the newer wrangler has a lower first and higher 5th gear than the outgoing model...

my point is, as transmissions improve, gearing at the axle becomes less relevant, unless your turning 37" tires and or want to use larger pinion gears for strength...

 

I found a good vin decoder on the site and ran it. The original build shows a 3.42 rear end. I reset the DIC mileage function and watched it. I am showing about 13.5 mpg on a 30 mile drive (I kept my foot out of it and traveled the speed limit). I understand the DIC may not be completely accurate and this wasn't much of an average driving mpg.
At 60 mph the tach was reading 2000 rpm.
I am 3/4 of the way thru a full tank of gas and will compute mileage on fill up.
Thanks for your replies.
Gary

 

pm me the last 8 of the vin and i'll send you the complete build sheet.

 

Thank you, pm sent. Gary

 

sent it.

 

Thank you very very much sir!

 

Well, I really did not believe the DIC when it said 14.8 mpg on this last tank of gas. But it was filled at the same pump as the last time. Miles \ Gallons computed to 14.7. That's at least 2.7 mpg better than I thought I was going to get.
Gary

 

here's a link to compare vehicles:
Compare Cars Side-by-Side
some years there are no 2500 series trucks however.
funny thing is there is not much difference between the small engine full size trucks and the big engine full size trucks.

 

I had 3.73 factory gears and then I installed 4.56 because of my 34 inch tires. But I was looking for complete axles with 4.10 gears but could not find them locally. I would have swapped my axles with someone's 4.10 axles and paid a little and done the work. The point is 4.10 axles are rarer than 3.73 and worth more. You may find someone who wants to swap. Also some axles have the gov-loc G80 locker factory installed and that adds some value.