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Thread: Tire size, gearing RPM question...

  1. #1
    Mud Puppy Grevus's Avatar
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    Default Tire size, gearing RPM question...

    what is the typical RPM at 55mph with 33's, with the following gears?

    3.07
    3.73
    4.10

    I'm just curious...
    `89 YJ 33's 4" lift, High-lined front and rear "The Mistress"
    ** NOTE TO SELF** it is illegal to stab stupid people in the eye with a pencil

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    Land Squid Jeffb_79's Avatar
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    Quote Originally Posted by Grevus View Post
    what is the typical RPM at 55mph with 33's, with the following gears?

    3.07
    3.73
    4.10

    I'm just curious...
    It's all going to depend on engine, transmission and transfercase.......

  3. #3
    Mud Puppy Grevus's Avatar
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    stock 4.2, auto tranny stock NP231
    `89 YJ 33's 4" lift, High-lined front and rear "The Mistress"
    ** NOTE TO SELF** it is illegal to stab stupid people in the eye with a pencil

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    Mud Puppy Grevus's Avatar
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    http://www.grimmjeeper.com/gears.html

    found what I was looking for
    `89 YJ 33's 4" lift, High-lined front and rear "The Mistress"
    ** NOTE TO SELF** it is illegal to stab stupid people in the eye with a pencil

  5. #5
    Mud Puppy Grevus's Avatar
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    Default here's what sparked the question..

    I'm running 33's and @ 55mph I'm at about 2000rpms...

    but according the the above calculator...

    3.07 - 1797rpm
    3.73 - 2089rpm
    4.10 - 2296rpm

    the tags on my axles say I have 3.07s but if this math is correct either the gears have been switched or something.. hell i don't know.. guess I will have to do some marking and counting..

    do R&P's have a stamp on them?
    `89 YJ 33's 4" lift, High-lined front and rear "The Mistress"
    ** NOTE TO SELF** it is illegal to stab stupid people in the eye with a pencil

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    Newbie Goody's Avatar
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    Jack you jeep off the ground and put it in nutral. Spin the both wheels at the same speed one full revolution and count how many times the drive shaft rotates. That will determine your gears.
    "If we weren't all crazy, we'd just go insane."
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    Junior Member Kevo's Avatar
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    Agree with jacking up and counting revs, but they are stamped into the ring somewhere. I like taking off the cover to verify on the ring and pinions with also checking locker/LS situation. Then adding quality synthetic fluid that will hold up to what I am going to do with the vehicle. Better safe then sorry on from diffs.
    Good luck with it.

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    Senior Member HillBillE's Avatar
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    Yep, the ring gear will be stamped, usually with 2 numbers.

    Divide the larger # by the smaller to get the exact ratio.

    Example: 10:41- 41 divded by 10 = 4.1, or 4:10 ratio.

    The numbers are the amount of teeth, 10 being the teeth of the pinion, and 41 the teeth of the ring gear.

    Most accuarte way to check, and only involves pulling the cover/draining the fluid.


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    darwinism at its best irish1371's Avatar
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    3.73 on 33" with a 5 spd 4.0 is about 1900-2100 at 60ish on mine
    "Some people wonder their whole lives if they will ever make a difference. Marines don't have that problem." Pres. Ronald Reagan
    Army vs Marines = http://www.youtube.com/watch?v=_2M7ckkxQLU

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