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can i tell my gear ratio with this info

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Confederate9, Sep 21, 2002.

  1. Confederate9

    Confederate9 1/2 ton status

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    hey guys, i need to know what gear ratio i have because i think my rear is goin out, and im searching for a new one just in case. but to my knowledge the rear axle is fully stock and on a 85, the specs said:
    8.5-in. 1.28 Axle Dia. 28 Spline

    am i able to know what gears i have?
    if not what other ways are there, i know the code thing, but i cant figure out what it says plus i don tknow the codes... are there any others ways, thanks guys
     
  2. milspecjimmy

    milspecjimmy 1/2 ton status

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    look in the glove box or on the door jam near the latch of the drivers door. youll see a list of of numbers and letters. 3 digits apiece. the gear ratio codes usually start with a G, and are some what like GU4, GU5, GU6 ect...im not positive of what each one is but some one on here may. and the dealer will definately know


    ~~~jeff
     
  3. 84K5cedric

    84K5cedric 1/2 ton status

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    The best way to find out is to pop the cover and count the teeth. Divide the number of teeth on the ring gear by the number of teeth on the pinion gear.

    ex. 41/11=3.7272727272 (rounded 3.73)
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Why count teeth when the ratio is stamped on the edge of the ring gear???/forums/images/icons/confused.gif

    Rene
     
  5. 84K5cedric

    84K5cedric 1/2 ton status

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    really? haha, didn't know... I just count /forums/images/icons/blush.gif
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The last 3 or 4 digits are the build date, the 4 digits in front of the build date is the ratio. For example my old 14 bolt reads "11 41 74 9" Built in Sept 74, 11 pinion teeth and 41 ring gear teeth...3.73's

    12 41 =3.42:1
    11 41 =3.73:1
    10 41 =4.10:1
    9 41 =4.56:1

    Rene
     
  7. POWERMAD

    POWERMAD 1/2 ton status

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    Or chock the wheels and put it in nuetral, then raise one side and mark the pinion.
    then spin the tire 2 times and count the turns of the yoke.

    just over 3 times is a 3:08
    about 3 and 3/4 turns is a 3:73
    just over 4 times is a 4:10
     
  8. m j

    m j 1/2 ton status

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    my favorite is the string taped to the driveshaft and roll the truck forward one tire revolution and count how many wraps the string now has on the shaft
     
  9. 84K5cedric

    84K5cedric 1/2 ton status

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    of course for a truly accurate check, a live chicken and a vat of virgin's blood is required. /forums/images/icons/tongue.gif
     
  10. m j

    m j 1/2 ton status

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    LOL
    of course
     
  11. POWERMAD

    POWERMAD 1/2 ton status

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    Let's not forget about if it is a locked diff, it only requires one tire rotation then.
     

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