IMHO 3.92/4.10 gears work just "okay" for stock 33's on a 4800lb RCSB 2WD R/T
...but I think a 5700lb Quad Cab 4x4 needs
4.56's especially for 35" tires, and even more so if it ever has to haul or tow anything.
The Ram 5 speed auto 545RFE ratio's
2nd Prime 1.50:1
We have TWO overdrive gears, but you wont use them properly if you dont re-gear your axles to return the truck to its optimum rpm range.
The 0.67:1 overdrive is more than enough to bring the rev's with 35's/4.56's down to almost the same a Ram with 3.92/4.10's and 33's
33/35= .9428 X 4.56 =4.30:1 net effective gear ratio
If you think that's too high, then consider the added weight of an M/T tire is substantially more than a Goodyear HP.
The increase in rotational mass plays a factor too, as does the added drag of the tread design.
FYI, a 37" Nitto Trail Grappler weighs the same (without Wheel!) as the stock Goodyear 275/60R20 does mounted on a stock 20" wheel.
...not to mention the increased negative effects on aerodynamics after lifting a Truck 4"-6".
Check out this chart for ideal RPM's based on 65 mph with a 1:1 gear ratio:
Now consider that the Final Drive in 4th is 0.75:1
Rev's with 4.56's and 35" tires at 65 mph = 2134, in 5th = 1906
Here's an online calculator
the one nearest the bottom allows you to input the final drive ratio
I've been lifting trucks, swapping tires and gears since the early 80's
, Re- Gearing doesn't kill fuel economy, Lifting and Putting Larger Mud Tires does...I've done it all a dozen times over.
My RCSB 4x4 is lowered and running 305/50R20 Grapples...about 32"x12" and I'm swapping my 3.55's for 4.56's.
I have a dedicated set of smaller 27" Drag Radials that give me an effective ratio of 4.30:1, the EVIC still reads 20 mpg at 65MPH/2000rpm
(Tire Size corrected with Diablo, speedo verified by hand held GPS)
My best economy with 3.55's pushing my heavy Grapplers is around 22 mpg on flat level ground
but if I get into some hills the engine lugs and has to constantly gear down and drop out of MDS....so MPG can actually be worse long range.
Going from 3.55's to 4.56's only changes the rpm's by about 400 with the same tire,
Going from a 3.92 to a 4.56 ratio and from a 33" to a 35" will be about 200 rpm's more at 65 mph