anyone have a link to some cheap rear 4.56 and thick front 4.56 ???

 

Check with Randy's Ring and Pinion, or drivetrain specialties. There are a boat load of other places too. Ebay had some package deals with gears, and install kits, not sure if you could custom order a set with the thick fronts though.

 

I was playing with a tire size vs gear =rpm with a excel sheet and came up with this.

Trans ratios from http://dodgeram.org/tech/transmission/4xre.htm


In O/D In 3rd

with 3.55 245/75R16 = 1757rpm @ 65mph 2546rpm
265/75R16 = 1691rpm @ 65mph 2451rpm
285/75R16 = 1630rpm @ 65mph 2363rpm
315/75R16 = 1574rpm @ 65mph 2242rpm


with 3.92 245/75R16 = 1940rpm @ 65mph 2811rpm
265/75R16 = 1867rpm @ 65mph 2706rpm
285/75R16 = 1800rpm @ 65mph 2609rpm
315/75R16 = 1708rpm @ 65mph 2475rpm

with 4.10 245/75R16 = 2029rpm @ 65mph 2940rpm
265/75R16 = 1953rpm @ 65mph 2830rpm
285/75R16 = 1883rpm @ 65mph 2729rpm
315/75R16 = 1786rpm @ 65mph 2589rpm

with 4.56 245/75R16 = 2256rpm @ 65mph 3270rpm
265/75R16 = 2172rpm @ 65mph 3148rpm
285/75R16 = 2094rpm @ 65mph 3021rpm
315/75R16 = 1987rpm @ 65mph 2879rpm

with 4.88 245/75R16 = 2415rpm @ 65mph 3499rpm
265/75R16 = 2324rpm @ 65mph 3369rpm
285/75R16 = 2241rpm @ 65mph 3248rpm
315/75R16 = 2126rpm @ 65mph 3081rpm

 

i have a off-road edition with 315/70/17s and i kinda wish i had 4.56 but the 4.10s do alright but i do have a few bolt ons which probbaly help somewhat

 

Sorry I don't understand what the ratio thing is saying....It seems that the rpms are lower with 4.10 but I could have no clue what I'm talking about that's why I'm on here lol

 

Look at the tire size you have now and look at the rpm's. Then look at the tire size you want to go to per each gear choice and match the original up to the new as best as possible. Make sense? or maybe I am wrong about this.

 

So from what I look at if your right is 3.92 or 4.10 match the best with 3.55 and 265x75 and going up to 315x75

 

Slider has it rite, find what you have and then what you plan on going to and best match up the rpm. Sorry for the mess I have made an attachment of it.

How to use this chart

Take your factory tire size and gear ratio and take note of the rpm, So if you have 3.55 gears 245/75R16 = 1757rpm @ 65mph and are going to a 315/75R16 you need to get it to the closest rpm the truck had from the factory 1757rpm rite, So a 4.10 with 315/75R16 = 1786rpm @ 65mph is the closest to a match.

 

So 4.10 would be better than 4.56 about what kinda mpg will I get ?

 

I like this chart for gear selection, however you'll have to multiply the rpm/tire/gear size by .8 to get your correct rpm in overdrive.

http://www.jeep4x4center.com/jeep-ti...atio-chart.htm

For instance with 4:56 gears and 35 inch tires you'd multiply 2845 rpm x.8 and get 2276 rpm.
BTW, this falls right in the peak torque range of a 5.2/ 5.9 gas engine, which is why most guys who run this combination notice thier trucks don't shift out of OD much.

Keep in mind there are other factors that reduce gas mileage. Running larger, heavier tires increases unsprung weight. Adding lift components to a truck increases weight, and lifting a truck with poor aerodynamics increases drag even more as more air is allowed under the truck.

In all seriousness, if gas mileage loss is your number one concern, I would not lift your truck or put larger tires on it.

EDIT: I would PM our moderator SilverDodge on your setup. He runs a 5.2 with 35 inch tires and 4:56's.