That should help you out.
http://www.4lo.com/calc/geartable.htm

4.88s are the lowest you can go in a 9.25 but that should bring your mileage back up. Even 4.56 if you don't do much offroading or towing.

 

Having trouble understanding this chart, seems the RPM's are all higher then what im thinking they should be?

When im doing 65 on the freeway, my RPM's are about 1600.

 

yah i would agree, id say that chart is quite high too

 

Thanks all for the help and advice, i'll be looking at the rearend gears Monday myself. The stamp says its 3.5 gears, which doesnt sound right to me. But it being a stamp doesnt mean they didnt go in and change the gears but left the stamp reading 3.5, so i'll findout Monday. Im hoping there too low so I canchange it and possiblyincrease theMPG.

Again thanks for all the advice, still willing to take in any other advice!
Will let yall know what I findout Monday.

 

Did you have your speedo recal for the bigger tires?
If not your actually getting better mileage.
You still need lower gears as your lugging the engine at too low an rpm.

 

this gear chart is a little more accurate IMHO:

http://www.drivetraindirect.com/t_gear_calculator.htm

 

I just got it recal'd less then a week ago. Nice to know how fast im actually going now.
The recal didnt seem to raise the MTG, if it did, im not noticing any difference.

 

If you wish to stay with larger diameter tires
consider the commercial 19.5 tires
like come from the factory on the 2007 model year Cummins 6.7 Ram cab/chassis model.

These 19.5 tires probably roll much easier than your large 'mudder tread' tires
which are probably a large factor in your poor MPG,
but you will need special wheels to fit the 5 on 5.5 bolt pattern on your present truck.

It is relatively easy to test whether your present tires are a cause of poor MPG...just find another Ram with stock factory tires and see if they will change out with you for a test.

Don't be afraid to ask a fellow Ram pickup driver, you might get turned down a time or two but you will find pickup driver's are friendlier than most and it is never a bad idea to know fellow Ram owners in your area.

Lifting the suspension also makes the truck much harder to push through the wind, and that is probably part of the MPG problem at interstate highway like speeds.

You will get bogus advice on forums about numerically higher differential gears improving your MPG in city driving. The safe way to find out for yourself that this advice is bogus is to purchase a GearVendors unit in 'underdrive' setup to install behind the trans, which will let you run like you are now, or with a flick of a switch run like you had 4.56 axles. The cost of a GearVendors is a bit more than the $ price to swap two diff gear sets front and back...but you can sell the GearVendors later on the used market for a substantial portion of the new price:

http://dieseltruckworld.tenmagazines...e&aid=2798

Much more MPG advice that automotive engineers agree with in this very long read:

https://dodgeforum.com/m_447500/tm.htm

 

buy a piece of crap import for $500. drive that when ever you can and use your truck like a sports car that sits in the garage.

or suck it up. lol like the rest of us [sm=signs003.gif]

 

remember that first gear chart is for 1:1 ratio, take off your overdrive and see how you match up.