Ring and Pinion

Discussion in '40- & 55-Series Tech' started by bulldog, Oct 22, 2005.

  1. bulldog

    bulldog

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    How can you tell what the Ring and Pinion ratio is (3:73, 4:11) etc. when the gears are still in the differential and the differential is out of the vehicle. I know that if the axle is still together you can turn the wheels and count the turns of the tire compared to the pinion to get the ratio, but these are out of the vehicle so I am not sure. Thanks in advance.
     
  2. e rock

    e rock

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    count the teeth on the ring gear. let this number equal 'x'

    count the teeth on the pinion gear. let this number equal 'y'

    x/y = gear ratio

    41/10 = 4.10

    41/11 = 3.73
     
  3. jnau99

    jnau99

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    I think there are markings on the ring gear that will tell you also. For the most part if they are fine spline pinions that is the only time you could have either of the two ratios. Correct me if im wrong but if it is course unless sombody changed it they should be 4.10. Even when there out you can still mark the ring gear then turn the pinion and see how many turns it takes to make a full rotation.

    bulldog: What cruiser do you have here? I just moved to hermiston. I've seen a blue square bezel running around. I have a Dark-ish blue and black 40.
     
  4. FJ40fiji

    FJ40fiji

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    you can get an estimate by marking the drive shaft and the tires in one spot each with chalk and then having a buddy drive it slowly. count how many times the drive shaft goes around for the wheel to go once. Almost four times? prorbably 3.73s, alittle more than four times around? 4.11s.
     
  5. FJ40Jim

    FJ40Jim The Cruiser Whisperer SILVER Star

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    37/9 = 4.11
    Standard US ratio on E-78 and 88-newer FJ's.

    37/10 = 3.70
    The standard US ratio for 79-87 models.
     
  6. e rock

    e rock

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    Thanks for that. I knew my numbers didn't sound quite right for cruisers, but the numbers worked for the purpose of demonstration.
     
  7. bulldog

    bulldog

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    Thanks for all the replies. I just picked up 2 complete diffs and they are 3:73.
     
  8. bulldog

    bulldog

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    jnau99 - I drive a red with lime green hood FJ40. Most of the time it is parked since I don't have enough seats for the kids.
     
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