im assuming thats 2wd? no offense but im claiming BS on over 20mpg with 4.10's at that speed on the highway with a 4x4 truck.

4x4 trucks with 3.55's arent really seeing 20mpg at 70mph....

 

Mines a 2X4

 

ok. ill believe ya, but its still tough to believe even a 2wd with 4.10's can get that kinda mileage at 73...

 

Seems odd to me also. My 2wd with 3.21's gets around 20 MPG at 75. 4.10's are going to have that motor spinning 28% more RPM's

 

i thinks its because the motor isnt bogging as much so its running at optimum rpms

 

Load is more important than RPMs. The stock OD on your trannys is pretty tall, there's no reason to gear the axles as tall as they do. Stock 3.55s I'm calculating 1750 RPM at 70 assuming stock tires are 32" tall, that's too low and lugging IMO, especially with MDS, 4.10s brings that up to 2000 RPM at 70, much better IMO..

FWIW I had an explorer with 3.27s, it would get nearly 2MPG better by not using 5th gear below 65..

 

Had dealer swap to 4.56 from 4.10 before I took delivery.

 

I get 19-20 if I keep it below 70 on the freeway with 4.10s(2wd,rcsb). I should have had them slip in 4.56s when I had the gears replaced when the pinion seal leaked lol.