Tire Size, Gears, & MPG's

T

TooLoud

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Nov 21, 2007
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hey all, what are you guys running for tire/gear combinations? i just swapped out 33's for 35's and saw a pretty significant drop in mpg's. truck is in my signature, i also added a kelderman air ride supsension which probably added an additional 500+/- lbs to the total weight of the truck, which does not help mpg either. trying to figure out if i want to go to 3.73's or 4.10's, seeing some combinations that others are using would be helpful or other idea's on how to get the mpg's back not set on changing gears if i don't have to. thanks
 
I have basically the same truck as you-2002 2500 3" lift, 6spd, 3.55s with 35s . My mileage dropped some, but I wouldn't call it significant though. 16 city and 19-19.5 hwy. What numbers are you getting? And are you figuring them by hand are by what your odometer shows? Don't forget that unless you cahnged the settings in your computer your mileage will read 9.5% low.
 
i was getting close to 19 mpg around town and 21+ mpg on the highway prior to the swap. i have the smarty programmer so i was able to adjust the speedo/odometer and i was calculating mileage by hand. i have been trying to fine tune the speedo with these tires to get as accurate as i can so i haven't down any mileage calcs yet. but i can watch the gas gauge and when i make a run that used to not even move the gas gauge and now i use over an 1/8 of a tank, that seems a bit off to me. maybe it is in my head but i know i could go back and forth to work on less than a 1/4 tank of fuel and i am now using over a 1/2 tank for the same trip. like i said it could be in my head but i don't think so in this case.

also along the same lines i have been told in the past to run my controllers up on higher settings to get better mileage as long as the right foot is kept in control, does this seem reasonable?
 
I'm running 265's with a 4.10 gear ratio. On the Highway I can pull 18-20 mpg depending on speed. In town it usually get between 15 and 16.5.
 
TooLoud said:
but i can watch the gas gauge and when i make a run that used to not even move the gas gauge and now i use over an 1/8 of a tank, that seems a bit off to me.
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Thats your problem, you have a gas gauge in a diesel!:hehe: J/K It could be possible that your gauge is starting to go out. The floats on our trucks is made out of some type of material that eventually deteriorates in diesel fuel. My gauge now is at a half tank when its empty. Thats a long shot though. I would bet you just need to check your actual mileage and compare it to what your odometer reads. Use a GPS if you can get a hold of one.
 
Did you calibrate or have the speedo calibrated for you new tire size? not knowing teh original tire size from teh factory, you are probable travelling more miles then your odometer is telling you, also your overhead MPG gage is not gonna be right no matter what you do.

I too have 3.55 gears and 33" tires, and my GPS says I'm about 3 off at 60, IOW, my speedo says 60 I'm actually doin 63, or 2.5 off at 50 which equates to 5 miles lost for every 100 miles travelled.

Also pushin 35"tires takes more power which will definately have an effect on your mileage, doubtful a 2 MPG effect. But between teh tires and and extra 500" additional weight? could be?

Anyone know the size tires that these came with? I've seen 245/75/16 and I've seen 265/75/16?
 
i will have to check the recalibration with my gps unit, didn't think about trying that, i usually try to go by one of the police portable speed units that seem to be placed everywhere this days. i think it is pretty close, i guess bottom line is i need to check it and stop going by gut feeling. mine came with 265's originally but i have also seen 245's.
 
my truck came with 245s originally and i up/downgraded to 315s and had my speedo recalibrated, and ive noticed that my average has actually gone up since then, my truck came with 4.10s from the factory so with the 245s i would run out of gears on the freeway around 80 or so, but now with the 315s and a corrected speedo, it doesnt seem to run out of gears and on the freeway i average about 22+ and in the city around 13. but then again my truck is stock motor wise
 
i have a 06 with a 6'' lift and 37'' tires. My truck came with 3:73 gears-ANYONE WANT TO TRADE FOR 4:10'S???!---
the daily dive isn't bad, but i just bought a bigger trailer.....
my 06 has a AFE intake, 4'' mbrp exu (something happend to the cat??-fell right off about two weeks after I bought it!), and a bully dog PMT. I get about 11 around town and 13-15 range high way. it does get a little better in the summer though. I live in up state PA with winterized fuel...

Maybe i should go lower than 4:10's , what do you guys think?
I would trade for 4:10's though! my truck has 31,000 on it.
I would think that anyone who has 33's or smaller would get better mpg with 3:73's. (thats the only way you can get a new truck is with the 3:73, unless you order it)!
 
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Flagg and tooloud, what gears do you guys have or did you have stock? I would have thought that the 245's would be on a 3.55 geared truck and 265's on a lower geared truck? I've also read that they come with 3.55's or 3.92's but it seems like 3.73's and 4.10's were also available.

LilBrown, your rig must have been screamin on the highway? when you could actually get it up to speed? 245's and 4.10's?
 
I get better mileage on 5x5 than any other setting on my comp its hard to stay out of the go pedal but it gets better mileage. prolly because its poutting more torque down to get the tires moving. It takes more fuel to get our heavy ass trucks moving than to keep them moving, hence the better mileage on the highway.

3.73s will compensate for the tire size and bring your rpms back to pretty much stock if you had 3.55s before. If you have 4.10s then 4.56s will get you back to stock and help out on the bottom end a lot.
 
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4.5" lift, front and rear replacement bumpers, 3.54's, 35's, automatic, with smarty and injectors at 72mph I get about 16mpg. Hopefully that'll go up with the smaller injectors.
 
4.10's / 305's / and everything in my sig - 13-14mpg city and 15-16mpg hwy.

got better mileage with 315's
 
monday 2-4-08, whent to the trans shop at lunch today. they said for me to bring it in (this wednesday) how i want it-low end added or not. and they'll set it up for what ever line pressure it needs. I'm gonna take it to them with it on. but I'm worried about my trip. 24-2,500 miles round trip with the trailer on the 13th. I'm hoping that a week it going to be enough to get a feel for it.



one of you guys who has 4.10's needs these 3.73's.....
 
thanks for all the input, i think i am going to go with 4.10's as i may upgrade size of tires to 37" in the future. as i drive it more, looking at where my rpm's are in different gears it is considereably lower than what they were, plus i guess i feel like i want to get back a little more on the towing side as well.
 
for me, in pa where it is somewhat hilly. i would say 3.73 up to 33'' tires.
4.10 up to 37'' and 4.56 and up.
that'll take the truck back to stock gearing, if you started with 3.73 on stock tires. I would go to 4.56 if i didn't drive soo much high way. and i'm only pulling 6,000lbs max.
 
I have 4:10s with 285s and my mileage is horrible. Last chck was 9.7 with about 10k behind the truck. 9 in town and 14.5 on the highway.
 
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