Gearing for 37's and streetmax

02bigstrokin

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Ok so I installed my Midwest diesel street max turbo this last weekend and got the tuning all squared away and man it runs awesome. So much better then the stock 14 turbo. The only little problem is with the lift and 37's and 22x14's and the little bigger turbo, 6th gear is pretty useless unless I'm running 70mph. So I know this has been asked a million times but what's the consensus on gears for a 6.7 with 37's? I'm thinking maybe 4.30's?
 

sootie

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ford 4:10 gearsets from sunrise would even do it.

Jared Rice has been thru this before...
 

6.7powerstroke

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Ok so I installed my Midwest diesel street max turbo this last weekend and got the tuning all squared away and man it runs awesome. So much better then the stock 14 turbo. The only little problem is with the lift and 37's and 22x14's and the little bigger turbo, 6th gear is pretty useless unless I'm running 70mph. So I know this has been asked a million times but what's the consensus on gears for a 6.7 with 37's? I'm thinking maybe 4.30's?

Hey I got 37 an 22x11 an think about going the street max .. What do you mean when 6th gear is useless unless running 70 .. If you don't mind would you mind posting some videos of a couple different runs I would appreciate
 

02bigstrokin

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Hey I got 37 an 22x11 an think about going the street max .. What do you mean when 6th gear is useless unless running 70 .. If you don't mind would you mind posting some videos of a couple different runs I would appreciate

What I mean is cruising at 55-60 in 6th gear isn't going to happen unless it's compltely flat ground. The turbo is just barely off boost enough where if you try and gain any speed or start up an incline it downshifts into 5th. So I just ride with it locked out of 6th gear for now. But 3.55 gears and 37's isn't a great combination to start with. You will love the turbo though
 

The Butcher

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4.30 is your only option. Ford factory parts. They increased the spline count on the pinion for the 14-15 model year, and there is no aftermarket 4.10 option as of yet. Sunrise has the 4.30 in stock (as of last week) because they ordered them in for me and we thought they were on back order so I got them locally. Then they showed up at Sunrise the next day! He should have them in stock. Just got mine back yesterday, so no reviews yet on how it does with the 4.30 ratio (and 38s), but I will drive it more today and let you know.
 
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The 2015's do the same. I have 35's and 3.55's and it downshifts at the slightest hint of throttle input. The 11-14 tunes we have mimic the 2015 tunes. If it doesn't downshift right away it can smoke more. They do it mainly to limit smoke and help with mileage so it will not lug.

We can run a tune that holds 6th harder. But it will smoke a little more.


Sent from my iPhone using Tapatalk
 

The Butcher

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Put about 100 miles on yesterday with the 4.30 gears. They definitely put some pep back in the step! On the low end it's about like it was with stock tires in terms of throttle response, speed, etc. Great power on the top end too. I noticed a pretty considerable difference in MPG though. Probably lost 2 MPG at 75MPH over the stock gears with 37" tires at 75MPH. New tires are 1" taller and 2" wider, but I didn't think there would be that much of a difference in MPG. Slowing down to 65-70MPH actually helped get it back to the range of where it was with the 37s and stock gears. Overall driveability has been improved with the 4.30s. My RPMs at 70MPH were right around 1900-2000.
 

02bigstrokin

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Put about 100 miles on yesterday with the 4.30 gears. They definitely put some pep back in the step! On the low end it's about like it was with stock tires in terms of throttle response, speed, etc. Great power on the top end too. I noticed a pretty considerable difference in MPG though. Probably lost 2 MPG at 75MPH over the stock gears with 37" tires at 75MPH. New tires are 1" taller and 2" wider, but I didn't think there would be that much of a difference in MPG. Slowing down to 65-70MPH actually helped get it back to the range of where it was with the 37s and stock gears. Overall driveability has been improved with the 4.30s. My RPMs at 70MPH were right around 1900-2000.

Thanks for the response! So I guess 4.10 would be about optimum then if highway driving is a concern too. But evidently like stated earlier in this thread they don't make a 4.10 yet for the 14-15. I may just get the 4.30's anyways. I don't do a ton of highway driving just maybe once in a while on the weekends to go ride the dirtbike. Other then that it's pretty much 55mph roads
 

Randy_270

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Put about 100 miles on yesterday with the 4.30 gears. They definitely put some pep back in the step! On the low end it's about like it was with stock tires in terms of throttle response, speed, etc. Great power on the top end too. I noticed a pretty considerable difference in MPG though. Probably lost 2 MPG at 75MPH over the stock gears with 37" tires at 75MPH. New tires are 1" taller and 2" wider, but I didn't think there would be that much of a difference in MPG. Slowing down to 65-70MPH actually helped get it back to the range of where it was with the 37s and stock gears. Overall driveability has been improved with the 4.30s. My RPMs at 70MPH were right around 1900-2000.

I just want to make sure I'm reading this right. You have 38x15.5s and 4.30 gears right now? At 65-70mph, you're getting roughly the same mileage as when you had 37s and 3.55s while doing the same speed? Or did you mean when you would do 75mph? Thanks.
 

The Butcher

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I just want to make sure I'm reading this right. You have 38x15.5s and 4.30 gears right now? At 65-70mph, you're getting roughly the same mileage as when you had 37s and 3.55s while doing the same speed? Or did you mean when you would do 75mph? Thanks.

Seems gas mileage is about the same at 65-70 between the two set ups, but a noticeable decrease in mileage now once you get up to 75-80MPH. I guess the taller lift height and larger tires start to play more into the equation with wind resistance, etc. This was very "unscientific" mind you since it was essentially noting the mileage on the lie-o-meter on the same 30 mile stretch going back and forth. Went about 80 on the way out, and then slowed it down to 65-70 on the way back. I'll have to start keeping track of it over the span of a few tanks report back my findings.
 

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