Im trying to determine the best overall gears for my
06 dodge ram 1500 laramie quad cab 4x4 5.7L
Hemi. I currently have 4" lift with 35x12.50r18 Toyo
Open country M/Ts. Its come time for me to
replace my pinion bearing because I can hear it
waring, but I was considering regearing the truck
while I'm there. I would want the front and rear axle
ratios to match up so I could run them together. I
currently get about 12mpg on average. Best fuel
mileage at 50mph (highest gear at lowest rpm), but
this is only because the 4 cylinder reduction eco
system never kicks in anymore due to the heavy
load. I hit it going downhill at times, but never
anymore. I'm burning up gas all the time running
these stock 3.92's. What would it take to get my
Eco mode back? But maintain power and speed
when I want. 4.10's be enough to get it the torque?
Or do I need to shoot for 4.56's? And if so, wouldnt
that be so high it would defeat the purpose of
reaching the 4 cylinder reduction mode? Also,
whats that mode called? MPS? Ive been told
before I have forgotten unfortunately. I appreciate
any helpful information.
And still being able to reach speeds of 80 mph confortably cruising! ^ If this is impossible, that's unfortunate. Just trying to find more than I know.
Your that making this backwards, the higher the numbers the lower the gearing, so low gear vehicles get worse fuel mileage than higher geared ones, but low geared toward units have more pulling power than high geared units, for example I had a truck that had 4.10 rear end gears, the fuel mileage was 9 per gallon, it didn't matter if it was loaded or empty, in town or highway, so I changed the rear differential with a unit that had 3.54 ratio, there was a noticeable differance in low end torque as it dropped some but my mileage went up to 15 on the highway and 12 in town, instead of the straight 9, so big ratio numbers equal high torque but bad fuel mileage and low top speeds, low numbers equal better mileage and higher top speeds but torque suffers. i can tell you that my current rig is running 3.75 ratios with 285/65/18 and I'm getting 12 in town and it will tick off 18 at 65 mph at a light throttle in top gear, of course 4X4 kills that, but you don't expect good mileage in 4WD. Hope this helped some.
Thank you for your response! I appreciate the knowledge you have shared, which was helpful but not exactly what I was looking for. I am aware of how changing the differet ratios affects the mpg. However, what im trying to achieve is reaching the MDS mode. The truck doesnt have the torque to run the MDS mode with the current gears. Lowering the gears would only make the truck lug more and have more strain trying to accelerate and hold speed. I want to take some of the strain off, reduce the lugging to help maintain speed. When the truck isn't having to lug to keep up it will shift into MDS mode like I want. So I'm trying to increase the gear ratio, to reduce the strain on the motor, (increasing torque/rpm), therefore allowing the truck to reach its MDS mode. I'm trying not to kick a dead horse here, just doing my best to explain my theory.
I looked up your recommended tire size and it showed 265/70/17 as stock and 275/70/17 as optional. So maybe that is your problem, it is taking too much engine torque to turn the tire and wheel combo you have on the rig.
Did you have the MPS system checked? There are some problems I am seeing on the Internet.
Yes sir, thank you. The trick is, I'm trying to keep my setup and make magic happen pretty much. Keeping my setup, just modifying my gears to accommodate the torque instead of my tires.
I have not, but I have seen no sign of issue with it. I'll conult with my local dealer and see if they detect any problems or can help me. Thank you
Try a good 4X4 shop, they may know of something that might get you where you want to be or at least close.
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