does re gearing after large tires bring back some mpgs??
i know it brings back the some power, but i was just wondering because gas is getting ridiculous down here. im 17 and my job doesnt pay enough for me to keep trowing gas in this guzzler with school and all.
my rig is an 04 4x4 4.6 with 37s. i was thinking 4.56 maybe 4.88s
thanks

 

I was wondering the same myself, I want to throw some 35"s on, but I will wait if I can't get close to the same mileage after re-gearing.


Jon

 

Someone needs to put a nail in this coffin for good. I have read countless threads on this forum and others on this topic and nobody ever has a definitive answer. There's the 4.88 crowd, the stay the same crowd, and the snide commenting "Don't drive a truck if you care about mpg's" crowd.

I have 35" tires on my FX4 with 3.73's. If money was no object, which gears would be better for MPG's, 4.10 or 4.56? I travel highways on a daily basis.

Thanks,
Anthony

 

All things being equal, the lower the engine RPMs you are turning, the better your mileage will be.

So, if you are running 35" tires, 4.10 gears should give you better mileage than 4.56. However, sometimes smaller gears will make the transmission downshift more, which increases your RPMs, which decreases mileage.

The larger number (lower ratio) gears do not make any more power, they just make you quicker off the line. Guys running large diameter tires would be bogging down off the line, if they did not also change the gears. Also, their tranny would be downshifting all the time.

 

Thank you.

 

With a set of 35" tirs on a truck going down the highway at 65mph in OD with the TC locked....


3.73 = 1630rpm ....

4.10 = 1790rpm.....

4.56 = 1990rpm...

4.88 = 2132rpm...


Now, depending on what motor you have and your towing/hauling habits are, the decision should be easy...

A 4.6 is going to need a few more revolutions than a 5.4....

And its just not the size of the tire, its the weight of them...


I personnally... would go no less than a 4.56 with a 35" tire....

If your paying good money to do a swap, make it worth while IMO.

Good luck fellers..

 

To the original poster:

The only way you are going to get any gas mileage back is take off the lift and big tires. PERIOD.

 

X2


If you can't afford or don't want to pay for the gas..... DON'T DO IT!!

And I'm almost certain a 4.10 will give you worse mileage than a 4.56 with 35's....

Its not just the figures I posted at 65mph...

Think about when your doing 40-45mph....

Your trunk will be downshifting like a ****...

You need to initiate TC lock-up to control heat.....Without a proper gear change, Your going to burn your slush box out...

 

fghfgjh

 

Yes adding deeper gears to your truck with taller tires can retreive some of your lost gas milliage.

bassically you want to calculate your overall gear ratio with your tires included and try to get back to that.

You will probably never see the same MPG as stock due to larger tires with more mass and surface area for wind resistance.

But i would think you could get within 1 mpg maybe 2 with the right gearing setup.

 

ok i see its not too bad on the highway, but i drive to school and work everyday and its got lights which leads to alot of stopping and going. and i think this is where it kills me is getting them rolling with that low gearing.

i drive my gf's truck and it only revs up to about 2k rpm to take off at the same rate as i do while im pushing up to 3k rpms. and think that is where alot of fuel is being burnt.

im not sure but hers is stock sierra 4.8 and she still gets like 12mpg.

im running 37s with 20s so its not all tire but still heavy i got you there, im thinking 4.56s

and does anyone know the stock fuel mileage on an 04 4.6?

 

You tell us....

 

dfgdfhg

 

Your truck is a 4 speed and when the torque converter locks up, it feels like a 5 speed...

So your first downshift is actually the TC un-locking.... Which creates the hydraulic barrier between your motor and the trans...

excessive downshifting is bad....HEAT!!

lag...

slow starts..


It all generates heat...

You should be able to notice when your hitting hills and down shifting into 3rd and 2nd..

not good IMO..

And on top of everything, going from a 3.73 to a 4.10 is not much change..

On my old truck, I went from a 3.08 to a 3.73 on 31" tires and gained a lot of power back, got my motor into a happy spot...

NO MILEAGE DIFFERANCE!!

I swear it got better....

 

if you have 37 on 20"s 4.88's for sure, and a rim tire combo like that you have to bankin or mommy and daddy better be bankin. And the 4.6l. Forget it, no *****, you best bet is programmer, 4.88's, good air fillter, and some kind of exhaust and be happy with whatever you get after that