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Discussion in 'The Hokey Ass Message Board' started by BigSherm, Nov 27, 2021.

  1. BigSherm
    Joined: Nov 12, 2021
    Posts: 18


    Hi Fellas,

    I’ve searched this board and others, but still have some questions.

    I’m totally inexperienced working on rear ends, but I’ve been reading.

    I want to replace my stock 3.92 gears in my ‘51 Ford F-1 (with 226 flathead six) with 3.07 for easier highway cruising.

    International Scout II carriers and 3.07 gears are cheap and easy to find used on eBay.

    I believe my stock diff and the Scout share a 26 spline pinion gear, so that makes installing my stock yoke on the new gears easy, right?

    What issues should I expect with my stock axles and the Scout carrier?

    Since 10-spline spider gears to fit my stock axles are are to find, can I reuse my spider gears in the new differential?

    The Scout has 27 spline axles.

    I think the correct inner axle bearings will allow my smaller axles in the Scout carrier, right?

    I suspect my F-1 only has 110,000 miles so my spider gears might still be useable, and my 226 flathead six is stock, so I’m not worried about needing extra-beefy driveline parts.

    And finally, I’m pretty handy with a wrench, and have successfully assembled an engine after a rebuild. I’m willing to try doing this myself for the first time, what do you guys think?

    Thanks, guys!

    Last edited: Nov 27, 2021
  2. TrailerTrashToo
    Joined: Jun 20, 2018
    Posts: 1,132


    It is many years since I owned an IH Scout II. Lets start with some basic questions:

    1. Are both the axles Dana 44?

    2. Are you aware of the Dana 44 carrier brake?

    3. Maybe some design changes between 1951 and 1971?

    rusty valley and stillrunners like this.
  3. BigSherm
    Joined: Nov 12, 2021
    Posts: 18


    Hi Russ.
    Yep, mine is the first year Dana 44.
    I am aware of the carrier break.
    That’s why I need a new carrier for the 3.07 gears vs. my 3.92 gears.
    It would make it much easier to just machine .32” off the bottom of the new ring gear, wouldn’t it?

  4. squirrel
    Joined: Sep 23, 2004
    Posts: 50,308


    It would be pretty difficult to machine the ring gear, after it's been hardened.....especially since you have to machine the surface that you'd mount to a machine....

    But anyways, have you read up on how to set up ring and pinion gears? They use shims, you have to get the correct pinon depth which you can do by either measuring (the pinion is marked on the end) or trial and error. You need to also set the pinion bearing preload, the backlash, and carrier bearing preload. The end goal is to get a good contact pattern, so the teeth are contacting each other near the center of the tooth.

    If you can find a donor vehicle of some kind that has 3.07 gears, and you get the whole rear from it, you can then do some measuring on the complete assembly to see how deep the pinon needs to be, before you do the swapping. And it'll have the correct carrier for the gear ratio. And you might even get a usable set of bearings, if you don't mind using used bearings.

    I did a gear swap like this years ago, I had a Checker Dana 44 rear that had a mangled end, but the gears were still good. I swapped them into the 44 rear in a 65 GMC pickup. I was happy with the result.

  5. Bird man
    Joined: Dec 28, 2009
    Posts: 713

    Bird man
    from Milwaukee

    3.07 is pretty lean for a little 6, Higher would be better. Finding a newer axle assy might be less involved.
  6. BigSherm
    Joined: Nov 12, 2021
    Posts: 18


    Thanks, Squirrel!
    I have done some research about setting up the ring and pinion.
    I can get the carrier and gears for about $200 total, which is a bargain.
    That would allow me to keep the original axle housing which is in excellent condition, and I like the idea of keeping most things original.
    What do you think about using my original spider gears in the new carrier?
    The new carrier should work with my smaller axles if I get the proper inner axle bearings, right?

    Thanks again,
    Last edited: Nov 27, 2021
  7. BigSherm
    Joined: Nov 12, 2021
    Posts: 18


    Hey Bird Man,
    My three speed has a pretty low first gear, and my 226 makes great torque down low.
    The truck will go over 75 per the GPS, but the engine is just revving too high at that speed.
    I know 3.07 would be a big RPM drop, but I like the idea of making the RPM’s at 60mph what they are now at 45mph.
    My wife’s’63 falcon has the same 1:1 in it’s three speed transmission, and does great with a 2.79:1 gear ratio and stock six cylinder.
    I think this would make 1st gear more useable on the street, too.
    Thanks for the advice, I’m open for more!

    Last edited: Nov 27, 2021
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,226


    This would be a concern of mine as well.

    That truck has the aerodynamics of a potting shed, and not much engine to move it.
  9. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,226


    There are two transmission ratio sets in your trucks year range. You say that you have a low first gear, so it would be safe to assume that you have the HD transmission, but I will list both, along with the combined effective ratio of each transmission gear, with the rear end gear:

    Non-HD high ratio:
    1st Gear 2.78:1: 10.9:1, 8.53:1
    2nd Gear 1.62:1: 6.35:1, 4.97:1
    3rd Gear 1:1: 3.92:1, 3.07:1

    HD low ratio (probably what you have):
    1st Gear 3.72:1: 14.58:1, 11.42:1
    2nd Gear 1.87:1: 7.33:1, 5.74:1
    3rd Gear 1:1: 3.92:1, 3.07:1

    Your new first gear with the 3.07 rear will still be lower than this truck without the HD transmission, assuming that's what you have.

    My advice is to take your desired freeway cruising speed and multiply it by 0.7832. Drive at the resulting number, and see how the engine performs under those conditions.

    For example, if you wanted to cruise the open road at 65, drive it at 50, and see how it likes the RPM. If you wanted to dare 75, run it at 60 (all rounded to whole numbers).

    While that does not take into account aerodynamics, that will put the engine at the RPM that it will be with the 3.07 gears, at the desired speed.
    Last edited: Nov 27, 2021
  10. BigSherm
    Joined: Nov 12, 2021
    Posts: 18


    Thanks, Gimpy!
    Does anyone have insight into my spider gears and smaller 10 spline axles working with the carrier meant for larger 27 spline axles?

  11. miker98038
    Joined: Jan 24, 2011
    Posts: 682


    I don’t know what Ford used in 51, but I’ve been thru the 55-56 bird/truck/wagon Dana “44”s several times. Some will tell you they’re really a 41 or a 45 or whatever. But there’s difference in the axles and the bearings. Sometimes in other internal parts. Some of those are getting hard to find. My bird has a truck rearend, no doubt swapped in somewhere back in its history. The taller bird perches were really poorly welded on. It was also warped and had to be straightened. So take a close look at what you’ve really got before you start spending money. You don’t want a snag in the middle that screws it up.

    Randy’ Ring and Pinion, now, was just north of me, and has been a good source of parts. Lots of 4 wheel applications, so they probably know about scout parts and interchange too.
    Hnstray and BigSherm like this.
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 50,308


    they were pretty good about putting the 44 (or 41 or 45 or whatever) number on the outside of the center housing, either on a lower web, or on top center above the pinion.

    Other models that are close to the 44, but not, use different bearing sizes, afaik.
    Hnstray likes this.
  13. I think you're asking if there is a bearing made that has the OD that fits the bearing caps and the ID that fits the carrier you want to use.. The axle spline has no "bearing" on the bearings you want to use but the side gears do. Do they interchange? I surely don't know, but I'll bet there is somebody on here that does.. Hopefully he'll see this thread.
    Hnstray and BigSherm like this.
  14. F-ONE
    Joined: Mar 27, 2008
    Posts: 3,073

    from Alabama

    Sorry. I think this is a bad idea all the way around and I say this with all due respect.
    There is a reason these 6cyl trucks came with 3.89 gears.
    What you gain at the "top" you take from the bottom and middle. There's no free pass. The less horsepower you have the more this is going to matter.
    Part of what helps these trucks slow is the gearing. So, you loose the "engine braking" yet increase top speed (in theory)
    Higher gears like the 3.07 may actually make the engine work harder (lugging/straining) than it does with the present gear.
    It's "peppy" now and can get to 75. With 3.07s likely it will be a slug and it may have a hard time even getting to where it can run now.
    Mileage will likely suffer due to reasons stated above.
    This can be a safety issue on hills and grades. It may do OK on the flats but on any kind of grade....What are you going to do about downshifting? Downshifting to 2nd is no problem in these....the issue comes when you run out of steam in 2nd and have to go to 1st.
    What about starting off, say at a steep grade intersection?
    Such a high gear and low power engine, gets into drivability issues.
    Do you really need to run 70 plus in a F1 Ford?
    These were low RPM engines that ironically like to run or were geared to run at the higher end of their RPM band.
    Why fool with the Scout Dana 4?? stuff when you can simply get a F100 9" up through 1972?

    My advice...3.07 is just too dang high for a Flat 6.
    If you must get a higher gear, forget the Dana 41/44...Get a F100 9". Choose a more reasonable gear. Nothing higher than 3.55.
    Hnstray, winduptoy and squirrel like this.
  15. winduptoy
    Joined: Feb 19, 2013
    Posts: 2,603


    I've always gone the 'okie ring gear change' route...taller tires give a longer rolling radius.
    look at that as an option
    BigSherm and pprather like this.
  16. I like taller tires and/or a transmission swap that includes some overdrive.
    Trying to combine parts from various rear axles sounds like an easy way to end up trying to combine non-compatible parts.
    Hnstray and winduptoy like this.
  17. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 2,778


    I looked into doing this swap about 15 / 20 years ago on my '51 F-1. The main problem I ran into was that my '51 was built with a Dana 41 and none of the driveline folks I talked to thought the carriers would transfer from the 44 into the 41. In the end, I took the entire Scout ('67 Scout 800) axle and put it under the '51. That was easy enough, the only things that had to change where the spring mounts had to be flipped to the other side of the axle, and I needed to run spacer plates on the axle ends. The Scout 800 Dana 44 had a considerably narrower track width and the wheel and tire combo I chose rubbed on the bed sides.

    In the end, with a 351W up front, M5R2 trans (.75 OD), and 3.08:1 rear axle, it is a great combo for cruising at 65+.
  18. I agree, the flat six is gonna be a turd with those tall gears. I tried that with my 52 F-1, it sucked. Would barely pull 65 on flat ground, any hill was a problem. This was with a stockish flathead V8, 3 speed and 3.00 gears. My solution was to swap in a T5 trans. Made the truck a pleasure to might want to check into it, lots of info on the web. You could keep your 3.92 gears if you went with an OD trans.
    BigSherm and Hnstray like this.
  19. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,226


    All around, that's probably a better plan.

    As long as it is the one with the 3.76 first gear, and not the 4.03 first gear.

    Then it will be like adding a higher top gear, and breaking up the spread below into better steps.
    BigSherm likes this.

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