Need some info with possible regearing

Discussion in 'Tech Info' started by Taylor_allen92, Nov 15, 2013.

  1. 97madness

    97madness Full Access Member

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    If ya want mpg. Take the huge wheels and tires off.

    Lower it (in a way you can return to lifted/stock) with the lightest possible wheel and tire (narrow aswell) you can afford.
     
  2. AKBray907

    AKBray907 SUPER *********.

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    With 35s and 4.56 gears with a 4r70w you'll be at 2200 rpm at 70 mph. Same tires and speed with 3.08 gears you'll be at 1400 rpm. You'll have no where near the power at that rpm and speed to maintain an you'd be lucky to stay in od at that speed. Your truck will have zero power with those gears but because of that will constantly be shifting to make up for it and raising rpm to gain power to maintain speed. Gears are a balance of tire size and the engine and trans inputs and outputs and where they run most efficiently at. So say you're running at 65 with 4.56 gears doing 2200 rpm, the consistent average and being able to maintain speed will be far better then trying to do 65 with 3.08 gears, the motor wouldn't even make enough power at that rpm to maintain the trucks speed with wind an tire resistance an would shift into 3rd gear an pop up to maintain speed.
     
    Last edited: Nov 19, 2013
  3. Taylor_allen92

    Taylor_allen92 Full Access Member

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    Now I see what you are saying, I thought that the tires had a part in why the recommended gears were higher than stock, but once they were saying to go to lower gears I second guessed myself and went with what they were saying since they have more experience than I do. :banghead: I want to stay at the height I am currently at and would like to keep these tires, I knew going into this that crappy mpg comes with a lift and big tires, but I am seeing several guys getting 13+ mpg running 35s so I am trying to get this sorted out. The higher gear ratio makes sense to me, I just got a little thrown off track when my co-workers said the exact opposite of what I had been reading/researching. I am thinking of doing 4.56s based on the numbers AKBray907 just listed, making a true dual exhaust, CAI, and possibly an electric fan conversion. I won't be getting the gears for another week or two, so I will continue to do research. Thanks guys!
     
  4. AKBray907

    AKBray907 SUPER *********.

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    Basically when you add big tires to the truck your essentially raising the gear ratio, the added weight and resistance and size takes longer to rotate one full rotation so if you threw 35s on there it's gonna feel like a stock truck with like 2.78 gears ( just throwing a ballpark number out there no specific math behind there) so to counteract this you throw in lower gears ie 4.56 and that'll bring your truck back to stock feeling basically. That's why most people go with 4.56 gear with 35s is because once you do the math it basically puts you back into stock range of the truck ie if you had stock 3.31 gears with stock 275/65 r17 tires ( 31.6") at 70 you'd be at ~2500rpm. So if you had 3.55s stock with stock tires you're at ~2600 rpm at 70. So that's factory what the truck is supposed to do at those speeds, so when you change to bigger tires you change gears to correct for the difference to try to bring it closer to stock range. So basically with 35s and 4.56s your truck will feel like a stock truck with stock tires and 3.31-3.55 gears and with 35s and 4.88 gears your truck would feel like a stock truck with stock tires with 3.55-3.73 gears and if you went with 35s and 5.13s your truck would feel like a stock truck with stock tires and 3.73-4.11 gears

    Hope this helps
     
  5. AKBray907

    AKBray907 SUPER *********.

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    The numbers don't convert perfectly but that'll give you a good idea
     
  6. J.Wal

    J.Wal Full Access Member

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    I have a bed cover, troyer E fans, gryphon with custom tune and 4.56 gears..... Average 14- 15 MPG when casual driving.... It's doable but cost a lot to get there.


    Sent from my iPhone using Tapatalk
     
  7. MyFX4Project

    MyFX4Project TRUCKIT

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    12-13 is pretty normal mpg with 35s. If you want the extra 2-3 mpg the e fans, custom tune, etc. will help you get there.
     
  8. Taylor_allen92

    Taylor_allen92 Full Access Member

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    Thank you AKBray907 for clearing that up, it makes perfect sense now. 4.56s it is!! But I think I will definitely do the e fans and possibly tonneau cover, but I will get a start on all of this very soon.
     
  9. BlackThundah

    BlackThundah Aka LilWhiteFiddy

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    Yeah I would NOT go with 3:08s. I had those in my last truck, which was a 2wd with a 4.2 and 33s and it was a dog. You had to floor it to get some perk out of that motor with those. Granted you have a 4.6, but like said you would kill the power of that motor with 3:08s. I know you decided to go with 4:56 I just felt like saying that. :jester:
     
  10. Taylor_allen92

    Taylor_allen92 Full Access Member

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    Ha thanks for the extra input man I appreciate it. That much more to back up my reasoning! On to the next question lol my grandfather mentioned that Ford could actually hook up their computer to my truck and reprogram the computer to compensate for the bigger tires (basically custom tune, correct?) so I gave my friend a call that works at a performance shop over by me and asked what he thought. I guess he works with a guy that does custom tunes on high performance cars and is appearantly really good, he said he would talk to him and see what he thinks he can do, said it should only cost $150-$200. Should I still upgrade my gears on top of the tune? I assume I would but figured I'd ask instead of just guessing.
     

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