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4.56 with 39's ????????

Discussion in 'The Garage' started by funkycold, Aug 4, 2003.

  1. funkycold

    funkycold 1/2 ton status

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    4.56 with 39\'s ????????

    I currently have 36" tires on my Suburban and 4.56 10 bolt. I have a 14FF 4.56 on the way. Will the 4.56 be adequate enough for the 39's I have waiting to go on or would it be best to go to 4.88 or 5.13. I mostly use it for DD but get offroad every once in a while.
     
  2. dhdescender

    dhdescender 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    It all depends on what your engine can handle.

    I'm running 4:10's with 39.5"s

    How? I have an engine with 345Hp & 500 ft-lbs of torque, and I manage to get somthing called 'mileage' b/c its not revving to hell on the highway.

    Addition: I also run dual transfers, So i can crawl aswell.
     
  3. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    Re: 4.56 with 39\'s ????????

    what tranny? i will be running 42+ and 4.10. BUT with a SM465. and some day a doubler.
    if i ever get the rest of the rig done....
    Grant
     
  4. funkycold

    funkycold 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    tranny...700R4
    currently run at 2400 rpm at 75 mph.
    8" lift, 10 bolts 4.56, 36" tires.......for now
     
  5. 4GUNZ4X4Z

    4GUNZ4X4Z 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    Answer: yes the 4.56's will be adequate enough for the 39's and 700. Now on the other hand if there is the slightes chance in your mind that you might go bigger tire size, then I would definitly give it some serious thought to putting 5.13's in your axles.
     
  6. zakk

    zakk 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    5.13's. i've made this argument many times
     
  7. outlaw612

    outlaw612 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    Ive got 4.56's now with my 36's and when I go to bigger tires the 5.13's will go in also.
     
  8. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: 4.56 with 39\'s ????????

    [ QUOTE ]
    tranny...700R4
    currently run at 2400 rpm at 75 mph.
    8" lift, 10 bolts 4.56, 36" tires.......for now

    [/ QUOTE ]


    Big Block, or small block?

    If your revs are at 2400... they are going to drop even more with the 39's. Sounds good initially, but I wonder where your engine's peak torque is developed? If you're way under the powerband the motor is going to be WAY inefficient and your mileage will reflect that.

    Also, I'm not sure how much "hunting" your 700R4 will be doing with that setup. You may find your truck dropping out of O.D. a lot....

    I've heard the 4.56 gearsets described as the "orphan child" of the chevy gearset series. A little bit too agressive for the 31-33 inch crowd, and not quite deep enough for the 36"+ crowd....


    Then again, who am I to talk....I currently run 4.10s on 38.5"s.... /forums/images/graemlins/shocked.gif
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: 4.56 with 39\'s ????????

    Zakk, there are drivetrain combo's that don't need to be that deep with 39.5's. 4.56's are ideal for my truck...6.2 diesel and SM465.

    2600 rpm at 65 mph...I could honestly use overdrive for freeway, but it keeps up with traffic just fine. Ideal rev's for the 6.2 would be closer to 2000 (torque peak)

    Rene
     
  10. txbartman

    txbartman 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    I run 4.56s with a 700 tranny and 42" TSLs. I do not use OD. If I were to drive the rig everyday, I would say that they aren't enough gear for that big of tire, but I bet they would be fine for 39s. My engine puts out plenty fo power (400+ HP, 450+ torque), but the weak link becomes the tranny. I will someday decide on the cost of a doubler versus 5.13s, but it is fine for me for now.

    My guess is you will be okay running 4.56s with 39s. Just don't hesitate to run in D if OD doesn't feel right. Costs the same to swap gears later as it does before, just more downtime. Something you might want to consider.
     
  11. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Re: 4.56 with 39\'s ????????

    Sounds good if you've got a doubler. Also good if you need to run a smaller tire at times, like a 35 for everyday driving and 40 for the trail.
     
  12. Shagnaz

    Shagnaz 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    I run 4.56's with my 700r, but if I could, I would do 4.88's or 5.13's. It's nice on the hiway, but everyone knows that running much over 75 mph is not safe in a rig that is lifted. I am guilty also.
    But, back to my point...You have overdrive and if you are going to stay with a 700r then go with something higher than 4.56's. BUT, if you plan on going to a T400, T350 or a manuel, then you need to stay with what you are planning to do. Specially if it is you DD like mine.
    I was cruising back from Windrock in Tn. @ 75 and got 16+ mpg.
    Future plan...
    And that is all I have to say about that. /forums/images/graemlins/thumb.gif
     
  13. funkycold

    funkycold 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    tx, being i do use my sub everday would you feel that i would lose anything by driving around in D vs.OD. only to put it in OD on the freeway vs. around town? and is the 14FF going to make any difference in this vs. 10 bolt?
     
  14. funkycold

    funkycold 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    Thanks Greg, i guess i will have to try it and see how it works before spending any money that i may not have to spend.

    Thanks for the /forums/images/graemlins/1zhelp.gif
     
  15. Aquaman

    Aquaman 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    I have the 4.56 and 39.5 ratio and sm465. I also have a modified 402 big block crate motor. It is fine for driving, and stuff, and mud, but anthing other than that (trails, rocks, HILLS), it's way too high. I am going to switch to the th400/np203/np205 combo, and see how it is then. If it still is too high, then I'll get 5.13's. I also plan to switch to 42's in the mean time.

    I think youre big problem is going to be keeping that 10bolt from braking.

    Zakk... how many MPG do you get? I don't have an odometer/speedo, so I have no clue as to mine.
     
  16. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Re: 4.56 with 39\'s ????????

    It should work ok, the biggest thing you might have problems with is your crawl ratio off-road.
     

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