Changing gear size

[TANK'S 250]

stock tire size ....................31.5"
stock gearing ......................3:73
stock tire weight..................51lbs(no wheel)
stock rpm's at 65mph in 4th gear...2,546

40" tire...............................40"
4:56 gearing.........................4:56
tire weight............................99lbs(no wheel)
rpms with new tire and gearing....2,490


so you would have LOWER rpms at 80 mph with 40" tires and 4:56 gears than a stock truck....

....4:56's....



I didn't know stock was 35"....where did this info come from?

but even if a stock tire was 35"(which I'd still like to see proof)....a 4:56 is still the best option by 50rpms...especially since you just added about 300lbs of rotational mass to your drivetrain(40" tires and wheels)

....and 300lbs in rotational mass is not the same as having 300lbs in the bed of your truck...rotational mass is completely different.

 

[eastern]

I looking into changing my gearing as well. I have 4:10 and pull my 4 place snowmobile trailer up north NY about 3 hours one way running 75 to 80 and rpms are at 25-2600 which kills my fuel milage. Don,t think I need low gears with the added power of tuning.I thought of 3:73 to bring the rpm's down. What are your sugestions? Also pull my 42' fifth wheeler in the summer with my 22.5 on.

 

[MadDiesel73]

3.73 - 4.10 for 35-36
4.10-4.30 for 37-38
4.30-4.56 for 39-41
4.56-4.88 41+

 

[TANK'S 250]

3.73 - 4.10 for 35-36
4.10-4.30 for 37-38
4.30-4.56 for 39-41
4.56-4.88 41+

yup...that is the same math I've always used....

...the thing people keep forgetting is...it's all about the transmission...our trans's are incredibly strong...but they still have limits...and it's a simple fact...if you don't regear when installing large tires...you are beating the hell out of your tranny.

Every person that has a temp gauge on their tranny knows...."proof is in the pudding"

I've seen guys run 40" tires and 3:73's...
does it work...yup...
does it raise their trans temps 30-50*...yup...
does it kill their fuel mileage....yup..
does it cause premature tranny/torque converter/cluth failure....yup

 

[TANK'S 250]

. Don,t think I need low gears with the added power of tuning.I thought of 3:73 to bring the rpm's down. What are your sugestions? .

Your tuner gave you more power....but it didn't magically make your trans stronger..

I looking into changing my gearing as well. I have 4:10 and pull my 4 place snowmobile trailer up north NY about 3 hours one way running 75 to 80 and rpms are at 25-2600 which kills my fuel milage. .

If you have close to stock size tires...3:73's will be fine... you may gain hwy mileage, but lose in-town mileage....and you will also lose some of your pulling power/torque....not much though

 

[cbrown]

TANK what is the math on those numbers you posted up with rpms/gearing/tire size? Id like to know how to calculate that.

 

[TANK'S 250]

I used a few things to get my math.

1. Door sticker for stock size tires.
2. Known stock axle gearing.
3. Interco's tire website for weight, size, and rotations on specific tires.
4. Gear chart.

Interco tire site:

http://www.intercotire.com/tires.php?id=2&g=1


Gear chart....

Note: This chart is based on a GAS engine rpm at 65 mph with the transmission in a 1:1 gear ratio
...but what ever the stock rpm's are in your diesel..it will be comparable with gear change...
....for example,,

3.73's, stock tires=2,200rpm's diesel...
4.56's and 40" tires will be roughly 2,150..diesel....which is almost the same as STOCK

NOW IF YOU WANT TO GET CRAZY....

WIKIPEDIA: Ford Superduty

4R100
Gear ......1.................2 ............. 3 ............4................ R
Ratio ......2.71:1.......1.54:1.......... 1:1 .......0.71:1.......2.88:1

5R110
Gear ......1................. 2 ..............3 ...........4 .............5..............R
Ratio ...3.11:1 ........2.22:1..........1.55........1:1.........0.71:1..... 2.88:1

5 Speed Manual
Gear .......1................ 2.............. 3............4...............5.............R
Ratio.....5.72:1.........2.94:1........1.61........1:1...........0.76:1... 5.24:1

 

[eastern]

Your tuner gave you more power....but it didn't magically make your trans stronger..





If you have close to stock size tires...3:73's will be fine... you may gain hwy mileage, but lose in-town mileage....and you will also lose some of your pulling power/torque....not much though

I have a full built suncoast and TC. (poof magic and a few $) LOL

 

[TANK'S 250]

I have a full built suncoast and TC. (poof magic and a few $) LOL

LOL...no question there...:rockon:

 

[cbrown]

So 4.30s would put me just under stock gear and 4.56s would be a little over, correct? I guess Im leaning towards to 4.56s, would still like to hear from anybody running that large of a gear on a race tuned truck. Just want to make sure it isnt super touchy.

 

[TANK'S 250]

would still like to hear from anybody running that large of a gear on a race tuned truck. Just want to make sure it isnt super touchy.

4.56's aren't large...5:13's would be though...





....but.....OK...here ya go..

I run an SCT II custom extreme track file, I have everyday for 5 years straight.....40" tires and 4:56 gears...
...It launches like a beast, and I get great highway mileage...

...happy?...


LOL LOL LOL LOL LOL


.

 

[cbrown]

Haha yea. And my rpms would be a little lower than yours also since I have an auto? Sorry for the stupid questions, the whole regearing thing is something I have general knowledge of/ know the reasons behind it, but not much experience with how everything relates together. Thanks for all the info though TANK, im definitely seeing it now.

 

[Jeff@Spartan]

4.56's aren't large...5:13's would be though...





....but.....OK...here ya go..

I run an SCT II custom extreme track file, I have everyday for 5 years straight.....40" tires and 4:56 gears...
...It launches like a beast, and I get great highway mileage...

...happy?...


LOL LOL LOL LOL LOL


.

Why are you posting about your 6.0 in a 6.4 thread? A 550-575 HP 6.4 is going to drive totally different than a 400 HP 6.0....

 

[TANK'S 250]

Why are you posting about your 6.0 in a 6.4 thread? A 550-575 HP 6.4 is going to drive totally different than a 400 HP 6.0....

It may be more HP....but....gears are gears are gears....and unless it has something different than a 5R110 in it....then my replies are valid...and educational.

Last time I checked,...when you buy gears....they aren't listed by engines...LOL LOL

 

[Jeff@Spartan]

It may be more HP....but....gears are gears are gears....and unless it has something different than a 5R110 in it....then my replies are valid...and educational.

Yes, your information regarding gears is great. The post I quoted, however, was your response to a guy asking about a "race tuned truck." A race tuned 6.0 and a race tuned 6.4 are totally different animals.....by like 150-160 HP. See my point?

 

[TANK'S 250]

Yes, your information regarding gears is great. The post I quoted, however, was your response to a guy asking about a "race tuned truck." A race tuned 6.0 and a race tuned 6.4 are totally different animals.....by like 150-160 HP. See my point?

ok...gotcha...the engine shot wasn't needed...but the rpm/speedo definitely is....

BTW- I have a touch more than 400 horsies...LOL LOL

 

[Breaking Habits]

My vote is for 4.10's. These things make enough low end torque.. the rpms wont be too high to bleed off economy either.

 

[TANK'S 250]

My vote is for 4.10's. These things make enough low end torque.. the rpms wont be too high to bleed off economy either.

the engine makes the torque....but the tranny will take the abuse for the lack of gearing...4:10's would be a waste of money...not enough change from the 3:73's

Engine HP has no business in a discussion of proper gearing for tires...

...sure...you could have 10,000hp,....but your 600hp trans is gonna blow up...especially if you don't gear for the tire size.

 

[Breaking Habits]

the engine makes the torque....but the tranny will take the abuse for the lack of gearing...4:10's would be a waste of money...not enough change from the 3:73's

Engine HP has no business in a discussion of proper gearing for tires...

...sure...you could have 10,000hp,....but your 600hp trans is gonna blow up...especially if you don't gear for the tire size.

true. i had 4.56's in mine with 38's and felt like it was too much. I'd vote 4.30 then I guess

 

[cbrown]

Jared, you say you felt that the 4.56s were too much. Care to elaborate?

Thanks