Bigger tires + Gear swap mpg?

mike905 · Apr 14, 2017

Currently have a leveled 8 speed with the 3.21s and 33's

What would be the difference in MPG if I add 35s (AT not MT) but also swap the gears over to 3.92 or 4.10?

yillbs · Apr 14, 2017

mike905 said:
Currently have a leveled 8 speed with the 3.21s and 33's

What would be the difference in MPG if I add 35s (AT not MT) but also swap the gears over to 3.92 or 4.10?

is it 4wd ? If so, you have to replace the entire front drive line, not just the gears, for the front that is. Going up to that tire without a gear swap will give you about 13-14Mpg on the freeway, going to a 3.92 will probably bring you down to about 11-12 or so.

808ram1500 · Apr 14, 2017

yillbs said:
is it 4wd ? If so, you have to replace the entire front drive line, not just the gears, for the front that is. Going up to that tire without a gear swap will give you about 13-14Mpg on the freeway, going to a 3.92 will probably bring you down to about 11-12 or so.

So you get less mpg with a gear swap???

mike905 · Apr 14, 2017

yillbs said:
is it 4wd ? If so, you have to replace the entire front drive line, not just the gears, for the front that is. Going up to that tire without a gear swap will give you about 13-14Mpg on the freeway, going to a 3.92 will probably bring you down to about 11-12 or so.

Yeah its 4wd, going to lower gears will give less mpg with bigger wheels? I thought it was the opposite

Iz48 · Apr 14, 2017

If you go with lower gears it will bring the rpms up higher, burning more fuel. If you keep the stock gears it would probably do fine when you get to speed but be sluggish getting there.

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crazykid1994 · Apr 14, 2017

I can't say for the older 4th gens but I get about 17-19 mpg highway depending on speed with the factory 33s with the 3.92 gears. I'm sure it'll drop going up to 35s because of the weight. But I can't see how it could drop all to much. I do have 4x4

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mike905 · Apr 14, 2017

So for me is there no way of improving mpg after throwing 35s on?

Pull Ya · Apr 14, 2017

Pretty much---weight reduction of your right foot, always drive with a tail wind or always drive down hill. 3.21's are about the best gears for mileage although you sacrifice some acceleration compared to 3.92's. The larger tires just make it work even harder, and they weigh more than 33's thus lower mpg. Also when you leveled the truck you will see a decrease in mileage, not a huge decrease, but a decrease nonetheless. Sorry for all the good news
Jay

Jwithing · Apr 14, 2017

You'll get better than 13-14 unless your foot is always in it. I have a crew cab 4x4, 3.92, 6 inch lift, 37x13.5x20, 93 Diablo tune w/ MDS delete and am getting 14.8 mostly cruising down the highway at 80mph. Just bought it 3 weeks ago, so my foot is in it often. If I drove 70 on the hwy, it would make a noticeable difference too.

Red5Point7 · Apr 14, 2017

Going with 3.92s or 4.10s would help I would think with bigger tires? Makes the engine work a little less as the lower gears help push the tires better. And with an 8 speed you could always manually put it in 7th or 8th on the highway and still be cruising below 2k rpms for fuel mileage..

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yillbs · Apr 15, 2017

going to a higher gear will cause you to use more gas, it isn't very noticeable until you add on the heavier tires. I have a 6" lift, with 35" toyo MT's and I get 12 on a good day. I have 3.21 gears. Those that say it's "sluggish " are highly mistaken, The truck has PLENTY of power, looks amazing, and can get through just about anything. I tow 7600 pounds behind it about 4 times a month, their is absolutley no sluggishness involved. I think going to a bigger tire is a good idea, the money you'll spend on the gear swap, which, will be in the 3-4k range because you're 4wd isn't worth the extra " umph " you get when you press the gas. It will be quicker, but it'll technically be slower, and it's not that much " quicker " .

Am3gross · Apr 15, 2017

how are you guys getting 13-14 mpg's, i am at 10 mpg, no towing no upgrades nothing..

yillbs · Apr 15, 2017

Am3gross said:
how are you guys getting 13-14 mpg's, i am at 10 mpg, no towing no upgrades nothing..

13 is hardpressed for me to get. Are you lifted? How large are the tires? The lift, and tires play a huge role in this. I have toyo MT's, they are 80 pounds per tire, pls my 6" lift , adds another 400 pounds in parts, so i'm heavy, I heve heavy tires, and I have more wind resistance.

It just depends on how high you are, how much you weigh, and how large / heavy your tires are. What are you running ?

I get about 12 with my setup, on a good day.
EDIT : FWIW when I'm going 55-60MPH, I can get 24-27MPG steadily, when towing, if i stay below 60MPH, I can get 14MPG, with 3.21's that's towing 7600 pounds behind me.

huntergreen · Apr 15, 2017

Mike, depending on the at tire you select, that alone can cause a 1.5 to 2 mpg loss. Figure in the extra weight maybe a little more. But that should put you in the ballpark for guesstimating your mpg.

Pull Ya · Apr 16, 2017

I leveled my truck(Bil's 2.1) and installed Michelin AT2's(stock size) and lost about 2mpg.
Jay

Bigger tires + Gear swap mpg?

mike905

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