Ran 4.88s for almost 2 years. helped offset the zero low end of the comp 273

 

The 4.88s are only for 2WDs for the record. I just wasn't sure if you were 2WD or 4x4

 

my opinion, but dashed with facts:

go 4.56:1.. don't even screw around with 3.92 or 4.1:1.. don't focus solely on RPM's as in indicator of fuel consumption.. it is, but it's misleading.. it's more about engine load..

explanation:

if you're running 1700RPM @ 70mph and you're loaded down (as indicated by a vacuum gauge), you aren't making any better economy than running 2kRPM @ 70mph and pulling a very low vacuum signal.. (the lower the better w/ vacuum)..

another way to say it: if you're tossing excess fuel into the combustion chamber attempting to achieve an RPM or MPH range, and the engine/selected gear is struggling to maintain or achieve that range, that fuel is wasted as incomplete burn takes place.. If you're running a lower gear choice, the engine has more leverage and doesn't struggle to maintain anything but the selected RPM range... it actually sips less gas..

another way to explain it: if you're tossing excess fuel struggling down the road trying to maintain an RPM or MPH range, you're running pig rich and there isn't much the engine can do but try to burn it- hence, it builds RPM's, which translates to MPH's.. but it's leverage is weak, so it consumes a butt load of fuel while running pig rich.. better leverage (as in lower selected gear) achieves the same ends with less effort, and instead of running rich your engine achieves stoich (14.7:1ish) air/fuel ratio, and 'planes' off maintaining that w/o effort..

these rigs are pretty dang heavy.. the EPA via federal mandates make the manufacturers maintain a certain overall MPG of their production fleet.. guess what? the EPA doesn't test them all.. what they do is yank out the calculator and type away- mathematically figuring MPG's based on factors they know.. you know what? that doesn't work.. it's a heckuva lot more complicated than that.. you wanna know what doesn't waste gas? an engine that isn't loaded- RPM's be damned.. furthermore, your hemi doesn't hit the power curve until well into the 2k's.. if you start up a hill, it has to build to it through less leverage on OE gears, w/ lower gears- it's riding along, sipping gas, engine less loaded- AND it's cruising just under the power band.. if a hill appears? if it DOES drop a trans gear, it will only do so for a fraction of what it would have to if it had to build 800+ RPMS to hit the power range..


you'll be disappointed with anything less than 4.56:1 I wager.. there are two effective o/d's in your trans, and your power band starts right at the range 4.56:1 axle ratio and 5th trans gear will have you @ 70mph.. it's a dang perfect situation, and what mother mopar should have offered stock- instead of appeasing a government entity that only knows how to use a calculator..

 

Just thinking back here and my rpms were a little higher with my 3.55's even after adjusting for your larger tires but anyway, when looking at your gear ratios, just use the % increase from 3.55 and multiply your rpms by that % to see where you would be. So if you think you want 4.1, (4.1/3.55) gives you an increase of about 15.5%. If you're sitting at 1600 rpm now, (1600*1.155) would have you sitting at around 1850rpm.

 

Go 4.56 you will not regret it. I went right to 4.56 after reading many posts, and taking Hammers and Weed's advice. Only regret is I didn't do it sooner.

 

I know if it wasnt so expensive to Gear a 4x4 that would have been my first mod!!

 

Gears won't affect the instrument readings, but pretty sure you won't be able to adjust for tire size anyway. The '03 has a separate TCM and the various tuners won't talk to it. You're better off to just determine the speedometer and odometer error and compensate. I do that with mine (the readings are 4.3% low).

 

Thank you Mike...My bullydog programmer just had an update a month or two ago, which I use to read DTC's, watch my temps (trans and coolant), watch engine load, and track my throttle position when I drive. Maybe it is able to talk to the computer better and actually do something more than be another gauge. I also use it to get a pretty accurate 0-60 and quarter mile time. Best 0-60 is currently 7.6 and quarter mile is 12.9. (right after doing the TM Delete mod for the 03) .

 

I thought the SuperChips 3815 worked on 03s for everything except trans tuning?

 

I've done a good bit of work (mods) on both an '02 and '03 Ram, both 4.7s with Superchips tuners and adjusted tire size on both with no problem...