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Front to Back Gear Ratio's

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Mingler, Nov 2, 2001.

  1. Mingler

    Mingler Registered Member

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    Front to Back Gear Ratio\'s

    I've been told that the gear ratio in the rear of the truck should match the gear ratio in the front of the truck. Is there any truth to this OR is it possible to run 4:10's in the front and 3:83's in the rear??

    Hoping someone will know.

    Thanks in advance
     
  2. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: Front to Back Gear Ratio\'s

    Sure its POSSIBLE, that is if you don't mind breaking your transfer case into tiny little pieces!!! [​IMG] YES, you must have matching gear ratios.

    <font color=red>GOT MUD???</font color=red>
    My license plate reads:<font color=blue> 8 YR SUV</font color=blue>
    <a target="_blank" href=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</a>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
     
  3. Stoopalini

    Stoopalini 1/2 ton status

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    Re: Front to Back Gear Ratio\'s

    The gear ratio needs to be the same in front and back or else you will bind up the drivetrain and eventually break something.

    The only difference you could get away with, would be a 1% varience.

    Ex) 4.10 in the rear, and the front could be anything from 4.059 to 4.141

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  4. 1Blazin71

    1Blazin71 1/2 ton status

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    Re: Front to Back Gear Ratio\'s

    Conventional thinking is that the gears must match. But there are those that say that as long as you stay within 1%-2% difference you'll be fine.

    In your case 4.10 / 3.88 = 1.07% so it should work.

    Check out this article on the Randy's Ring and Pinion site:
    <a target="_blank" href=http://www.ring-pinion.com/gear/g0398.html>http://www.ring-pinion.com/gear/g0398.html</a>

    Matthew Meyer
    matthewm@inhollywood.com
    '71 Ochre K5 - 4" Lift 35"s
    ZZ4 350 - 700R
     
  5. Mingler

    Mingler Registered Member

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    Re: Front to Back Gear Ratio\'s

    Thanks a Ton Guys.
    I guess i'm buying TWO lockers :)

    Cheers.
     
  6. 1Blazin71

    1Blazin71 1/2 ton status

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    Re: Front to Back Gear Ratio\'s

    oops...I read the math wrong in the Randy's article..

    Your 4.10 / 3.88 would be almost 7% difference...not good.

    Matthew Meyer
    matthewm@inhollywood.com
    '71 Ochre K5 - 4" Lift 35"s
    ZZ4 350 - 700R
     
  7. SlyDog

    SlyDog 1/2 ton status

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    Re: Front to Back Gear Ratio\'s

    Yea NOT GOOD [​IMG]

    <font color=green>[​IMG]1977 K5 GETTIN IT AWN[​IMG]</font color=green>
    GO BUSH
     
  8. michaelm

    michaelm 1/2 ton status

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    Re: Front to Back Gear Ratio\'s

    mud boggers run wildly different ratios front to rear
    what is the application you are refering to
    Quagmire is one example of the need to run differing gear ratios, he runs ?40s? up front and HUGE out back and did the math to get the final drive to the ground to be equal
    for the rest of us they must be the same
     
  9. 2cocky

    2cocky Registered Member

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    Re: Front to Back Gear Ratio\'s

    Some mud boggers set up their tucks so that the front diff is numericly lower this getts the front spinning faster then the rear they do it in hopes of getting the front to "float" over the mud, sence they run in the mud there is lots of slipage at the tires so they don't break the t-case. But for everyone else that 'wheels you would want to have matching front and rears.

    OOOPS....I THINK I JUST RAN OVER YOUR JEEP THING!!!!!
     
  10. gator1959

    gator1959 Registered Member

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    Re: Front to Back Gear Ratio\'s

    I have a Dana44 front w/factory 4.09 and the 14 bolt rear is 4.10/4.11 that is the farthest apart you can safely get if the truck drives on the interstate.

    '79 K-5,D-44HD(8-bolt),14 bolt(FF),4.09 ratio,427 rat,auto,38" rubber,currently taking body off frame
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Re: Front to Back Gear Ratio\'s

    Keep in mind, it is final gear ratio that must be within 1% or so. You can have different gear ratio's front to back as long as the tire diameters make the final ratio within 1% front to back. Generally speaking most of us run the same size tires (don't have to carry as many spares), so we need to have ring and pinion ratios that are within ~1% of each other. Abnormal tire wear, different brand or size tires, etc can also factor into the equation as well.

    General rule for street guys, run same brand/size tires and keep the R&amp;P ratios within 1%. Hope this helps.

    See my rig at <a target="_blank" href=http://coloradok5.com/gallery/Leadfoot>http://coloradok5.com/gallery/Leadfoot</a>
     

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