37x12.5 w/ 2.5 Icon?

[7.3 Whitey]

What kills the mileage is the rpms before shift.
Example:
stock tires 1600 Rpms in 3rd then 1250 after.
My 35s I have to wait until 1750 rpms before I shift into overdrive. Makes it very hard to just pass someone because when you put into the pedal, it instantly shifts down and then shifts into overdrive, drops the Rpms and you lose your powerband. Then you run really high boost which KILLS mileage. More air always means more fuel.

 

[VanoFord]

Can you explain the math and if sarcasm is involved?

No sarcasm. This math formula is a way to determine new R&P from tire increase/decrease to keep the power train back in factory specs.

Example:

(New Tire DIVIDEDBY Original Tire) TIMES Orig R&P = New R&P

(37/34)*3.73=4.06

I used this formula for my 06 Fifty

(35/30)*3.73=4.35

So I put a set of 4.30 in the back (2wd truck) and the truck ran like a beast. 65mph and I barely cracked 1800rpm 4.6L engine.

 

[LovinPSDs]

Whitey, who's tunes are you running? My will stay locking in overdrive for pretty much anything over 55mph. When i roll into the skinny pedal the boost comes on but I don't really down shift unless I'm pretty well laying into her

Side note - at 80 i'm running spot on 2K rpms

I really wish the truck had 4.10s outa the box but o well

 

[7.3 Whitey]

Little low on the rpms.
On the math thank you.
Mine would be (I think on an 02 F250, not sure on the specs of a stock tire)
On edit:
Stock tire is 265/75-16
265mm is 10.43(I'll say 10.5)
10.5*.75=7.87
7.87*2=15.5+16=31
35/31*3.73=4.211
If I went to a wider 33 like I plan
33/31*3.73=3.97
Correct?
And where do I find THAT gear ratio?

 

[LovinPSDs]

The general idea in the 6.4 crowd seems to be that with 550hp on tap 35s and 3.73s work we'll. not sure if you truck is built or where your at but I don't really mind the way mine is setup.. 4.10s factory would be nice but no way in hell would I go through the trouble of swapping now... Wayne even runs 38s on 3.73s, 35s aren't bad at all...

Isn't it alil hard to compare a 5speed to 4speed anyway? Or am I missing something

 

[7.3 Whitey]

It is until you think about it. Overdrive on both trucks is similar. My third gear and your fourth gear are equal 1-1 ratio. Those are the drive gear. All they did with the 5r is basically split up my second gear into two (your second and third) and lower the first. So at the drive gear , your 4th and my 3rd, we are equal. Overdrive I'm not sure yours may be a little lower because of rpm capability. But no matter what, if you put bigger tires than stick you lose mileage regardless of power.
You spread out all the gears into lower ratios with big tires. Factory shift points at the NEXT gear are always the same. Your trans won't let you shift any earlier because the next gear needs to have a certain rpm to shift. Even if you baby it you still have to stay in your drive gear a little longer until you can shift into overdrive. Rpm numbers may be different than mine unless your in 4th is compared to my third.

 

[flippincgfighter]

Doesnt a 5R not shift into 4th unless tow haul is on?

 

[BBottoms]

Doesnt a 5R not shift into 4th unless tow haul is on?

I think they skip a gear, depending on load conditions, in factory configuration. Once tuned though they use all gears. I know mine shifts 1-2-3-4-5 with Gearhead tuning.

 

[VanoFord]

Little low on the rpms.
On the math thank you.
Mine would be (I think on an 02 F250, not sure on the specs of a stock tire)
On edit:
Stock tire is 265/75-16
265mm is 10.43(I'll say 10.5)
10.5*.75=7.87
7.87*2=15.5+16=31
35/31*3.73=4.211
If I went to a wider 33 like I plan
33/31*3.73=3.97
Correct?
And where do I find THAT gear ratio?

there is a 3.93 gear, however I dont believe they make it for our trucks, and if they do, i dont think that one comes in a reverse cut (front diff). The 4.30 is the same. no Rev cut so you either run 4.10 or go to 4.56

The general idea in the 6.4 crowd seems to be that with 550hp on tap 35s and 3.73s work we'll. not sure if you truck is built or where your at but I don't really mind the way mine is setup.. 4.10s factory would be nice but no way in hell would I go through the trouble of swapping now... Wayne even runs 38s on 3.73s, 35s aren't bad at all...

Isn't it alil hard to compare a 5speed to 4speed anyway? Or am I missing something

as of right now, my truck is totally stock except for the level and shocks. after i sell my house this summer, i plan on stud/delete dpf & egr/NL CAI and just run a nice 600-650 knowing I have plenty more if need be. not gonna be hotrodding, just doing the studs for piece of mind, and deleting for MPG.

keep the trans talk and anything else related to lifting up to a 37. i enjoy learning. opcorn:

 

[7.3 Whitey]

there is a 3.93 gear, however I dont believe they make it for our trucks, and if they do, i dont think that one comes in a reverse cut (front diff). The 4.30 is the same. no Rev cut so you either run 4.10 or go to 4.56

So you will recommend going with a 4.10 and 35s. Hmmm. Wanted the wider, slightly taller. My truck is pretty tall for someone only 5'11". I want no running boards either.
I will look into it and post if there is a 3.93 gear ratio.

 

[VanoFord]

So you will recommend going with a 4.10 and 35s. Hmmm. Wanted the wider, slightly taller. My truck is pretty tall for someone only 5'11". I want no running boards either.
I will look into it and post if there is a 3.93 gear ratio.

I actually recommend 33's and your current gearing. My truck from the factory had 34 w/ 3.73. You should be good I would think.

 

[7.3 Whitey]

Yeah. But factory gearing in an old truck like mine came with 31s, simply because of the (similar to a Company that starts with a Dodge and ends with -ings) lack of rpms. Max out at 3500 not 4k+. It would be so nice because my truck, at least right now, is loooooving 2250-2750 rpms. I know 6.0s and 6.4s go through those EVERY time you drive. Its just so loud in a 7.3 and sloooooow lol.
I will go 33s stock. Because unless its a gasser good luck finding that gear ratio.