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Technical 1958 Ford F100 rear end ratio. What the????

Discussion in 'The Hokey Ass Message Board' started by Clyde Walker, Jun 7, 2019.

  1. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    I don't have the experience level of many of you on here, but in thirty odd years of hobby hot rodding I have never seen this...
    I brought a 1958 straight six, three on the tree f100 home last winter. The truck had a retrofit AMC 232 with Ford three speed manual transmission in it. I can tell this was at least the third engine it has had in it (go figure right?).
    I digress.
    It has what appears to be the original 9" rear end (fill plug in the back of the axle housing as apposed to the center section).
    Heres where it gets weird.
    Last winter while the weather was bad I did all the brakes. While I had it up I gave the rear end a spin to check the ratio.... 1.5 to 1 !!!!!! (rough guess marked tire/counted).
    Rubbed my eyes, did it again........
    1.5 to 1......Whaaaat?
    So for the time being since I had many bigger fish to fry with this old guy I left it to later in the project.
    Now we are at that point. Pulled the 232 this week to install a 272 Y block.
    Had my son over to help (my NEW back). We were talking about that gear ratio and I had him roll it around.
    1.5 to 1 (rough guess marked tire/counted). He got the same thing.
    What gives? The tallest gears I am aware of for the 9" are if I remember right are 2:47 to 1.
    Any body have any ideas??
    Should be great on the E way. The theoretical 172 mph top speed sounds exciting!
    (uh, yeah, good luck with that.)
    But ooof this will be a dog! I dont mind pulling the center section and having a gearset installed. I am just curious as to why/how this has this ratio. Glove box plate says 223 I-6/three speed manual/3:90 to 1.
  2. RmK57
    Joined: Dec 31, 2008
    Posts: 1,818


    Be a bitch to start off on hill with 1.5's in there. So when the tire makes one full revolution the driveshaft only turns 1.5 times?
  3. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    Yes. Triple quadruple checked this. I cant imagine what the intention of this ratio is.
  4. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    Oh it gets better. I am going to run an Air cooled 3 speed Fordomatic that leaves in second gear!
    Luckily I live in the flats but still...

  5. squirrel
    Joined: Sep 23, 2004
    Posts: 49,494

    Member need to turn BOTH tires one turn, not just ONE tire. Or turn one tire, two turns. (something about how differentials work)

    It's likely a 3.0 ratio.
    Just Gary, Johnny Gee, RMR&C and 5 others like this.
  6. What squirrel said.
    Joined: Oct 16, 2018
    Posts: 310


    Both tires need to rotate to calculate the ratio. It isn’t even possible to get a ratio that low in the confines of a 9”.
  8. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    Yay! Thank you. I will try that. It's an open so when I spin one the other tries to turn in the opposite direction. So make them both go in the same direction.
  9. With a open rear end just turning one wheel since you have the spider gears that only gives you 1/2 of the ratio. 1.5 x 2 = 300. the sure fire way is to pull the pumpkin & count the teeth on the ring gear and the count the pinion teeth. and divide. You truck originally if it was a stick likely would have a 390 or 411 rear.
  10. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    Just talking to my son (uh yeah, my NEW eyes too). He thought he was getting more like 1:7 or 1:8 to 1 so this is starting to sound more like what that tag is saying. Thank you guys!
  11. back in 65 I got a 56 ford HTP. I borrowed the 352 interceptor engine from my mothers 59 ford car. that had a bad crusomatic trans. Put a stick behind it. and promptly blew the rear end . So I swapped rears with the 59 to get the nine inch. It was 300 to 1 ratio. Dad had a 58 truck the hyd clutch was leaking and engine shot. So I swapped rear chunks. I now had a 411 and dads old truck now had 300's! Maybe you have dads old truck?
  12. 3.55 was a common ratio.
  13. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    I will be at it again here shortly. I will spin both tires, watch pinion yolk.
  14. alanp561
    Joined: Oct 1, 2017
    Posts: 1,736


    For an unlocked rear end, mark the yoke and housing directly across from each other. Mark a rear tire and the fender directly across from each other. While someone is rotating the tire two full revolutions, count the number of times the yoke turns. Same procedure for a locked or limited slip rear axle except rotate the tire once.

    Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
  15. 41rodderz
    Joined: Sep 27, 2010
    Posts: 5,440

    from Oregon

  16. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,065


    Don’t just spin one time, spin it ten times to get a more accurate count.... then move your decimal point one notch.

    Old wolf likes this.
  17. Ive never seen a pinion yolk. Ive seen egg yolk. when it hatches what does a pinion look like? Now I have seen pinion yoke's LOL
    Boneyard51 likes this.
  18. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,980

    from SW Wyoming

    They do have a good amount of iron in them, kinda tough to chew though.
    Old wolf and Boneyard51 like this.
  19. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    Old wolf likes this.
  20. Clyde Walker
    Joined: Aug 11, 2016
    Posts: 20

    Clyde Walker

    Ha. Well that’s what ya get when your eggs are as scrambled as mine! Yolk yolk yolk
    s55mercury66 and Old wolf like this.

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