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Technical Narrowing Rear End Question

Discussion in 'The Hokey Ass Message Board' started by thegearhead, Jan 23, 2019.

  1. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    I'm hoping i got this right? (measuring with drums and from wheel mating surface)

    Original rear end is 41.5" Wide New rear is 54.5" wide
    Original yoke is centered New rear yoke is offset 3/4"
    So i know i need to shorten it 13" but order to center the yoke i should have to take
    7 1/4 off long side and 5 3/4 off the short?
    This my first time doing this so not sure hoping someone can chime in.
     
    chryslerfan55 likes this.
  2. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,394

    fiftyv8
    Member
    from CO & WA

    I'm no expert on this stuff, but I would suggest what ever your plan, that you make sure you have axles the correct length to match any housing changes...
     
  3. What's the offset of old and the offsett of the new again?
     
  4. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    The new rear @ 54.5 w/ .750 offset would make one side 27.625 & the other 26.875
    The existing rear @ 41.5 w/ centered pinion would make each side 20.750
    Then 27.625 - 20.75 = 6.875; 26.875 - 20.75 = 6.125
    To test 6.875 + 6.125 = 13" ot 54.5 -41.5
    Thats a narrow sucker, drag race?
     
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  5. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    I’m having the original axle’s resplined.
     
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  6. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    If you want to narrow a rear axle the Ford full size van, rear wheel drive, is a popular one. The reason is that the engine and differential are offset to the right. The right side axle is about a foot shorter than the left. This means you can shorten the left side of the housing and use a stock right side axle shaft.
     
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  7. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    30EFBAB3-7135-401F-AAB6-5D926FD1689A.jpeg
    Thanks! And actually no that’s factory width for car lol
     
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  8. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    Is that a Timkin?
     
  9. redo32
    Joined: Jul 16, 2008
    Posts: 2,137

    redo32
    Member

    O.K. Since you won't mention it I am forced to ask.... What kind of car?
     
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  10. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    It's a 50 Crosley haha Built in good ol Cincinnati Ohio
     
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  11. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    Where are you taking these measurements from?
     
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  12. DDDenny
    Joined: Feb 6, 2015
    Posts: 19,144

    DDDenny
    Member
    from oregon

    Yep, numbers are your friend!
    Light bulb moment time.
     
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  13. redo32
    Joined: Jul 16, 2008
    Posts: 2,137

    redo32
    Member



    Well don't be embarrassed. I've got some Crosley parts in my backyard too!
     
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  14. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    Axle flange to axle flange with drums on for overall width.
     
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  15. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    o really? I wish i could find parts around here but i'd have just as much luck finding em in the middle of the ocean
     
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  16. seb fontana
    Joined: Sep 1, 2005
    Posts: 8,444

    seb fontana
    Member
    from ct

    At 41.5 I knew it was a Crosley..Your measurements are ok; be sure there is enough meat on axles to re-spline at shorter length..I would be interested in all four brake drums if you want to part with them..
     
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  17. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    Well I actually got rotors on mine but i do have a rear and front axle out back that has drums but there's only 3 2 front 1 rear. I wont be using those if any interest.
     
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  18. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    Dont mess with the offset (unless for some reason you need it) measure off the pinion center and the new flange, and remove enough material to get to 20.750 and repeat on the other side
     
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  19. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    Some guys are anal about having the housing centered in the frame (including me) Some are equally anal about not having the driveshaft angle over to the right as it comes from the trans to the rear even though every Ford with a nine inch since 57 had exactly that with no issues except when Chevy guys spotted the driveshaft. No big deal for most Ford guys a shit your pants cause that is all wrong according to Chevy guys.
    Axles have to be shortened the exact same amount you shorten the tube not to 1/2 of the total end width after you shorten the tubes.
    You can get pretty narrow with one as my bud's rear shows. I can't remember the WMS to WMS but it is narrow.
    [​IMG]
     
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  20. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 9,214

    mgtstumpy
    Member

    A handy reference to calculate axle lengths
     

    Attached Files:

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  21. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    Doing a little more research and seeing that most all GM 10 bolts like the 7.5 where factory offset 1/2" This being the weakling 6.5 10bolt i might of been of on my offset not being 3/4 but actually 1/2 if so i'll just run that slight angle. Or could always set it to center pinion and run a wheel spacer on one side.
     
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  22. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,394

    fiftyv8
    Member
    from CO & WA

    Will diff offset to the side (assuming angle calculated) compensate for pinion angle that is normally built in during a project build???
     
  23. Desmodromic
    Joined: Sep 25, 2010
    Posts: 571

    Desmodromic
    Member

    As I would define "offset", if it's 3/4", the axle housing tube on the passenger side is 3/4" shorter, on the driver side, 3/4" longer. The difference in length between the two is therefore 1-1/2", so i would agree with Gearhead's initial calculation. (Note - this assumes the replacement rear end has equal length axle housings, even though the pinion is offset. This is not necessarily true, e.g., the half ton Thames panel truck.)
     
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  24. Desmodromic
    Joined: Sep 25, 2010
    Posts: 571

    Desmodromic
    Member

    There are other aspects to be considered in determining the desired shortening.

    If the application is for a stock bodied Crosley, which you're repowering but want to keep original looking, you're on the right track. If you're building a mini-gasser, with wide wheels, you need to resolve where you want the rear tires to be; inside the body, protruding a few inches, or what? The Crosley has a rear track of 40". (Note - not the same a the flange to flange dimension.) Sedan/wagon bodies are 49" wide. The Hotshot/ Super Sports is 51" wide, looks a bit silly with the 40" track. I put 1" wheel spacers on my SS, to get the wheels in the correct place relative to the body.

    Looks to be a Vega/Monza et al rear end that you're using, which of course are the same bolt pattern as Crosley. And I think I see Crosley discs on the front. The calipers are not too good. I'd look into adapting motorcycle calipers, or some single pot type off small oval track race car. I've run across these for about 10 bucks apiece at swap meets.

    If you get in a bind for Crosley pieces, let me know.
     
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  25. thegearhead
    Joined: Nov 23, 2015
    Posts: 51

    thegearhead
    Member

    I'll measure axles today i believe they were the same length as each other. Brakes are disk now the rear will be drum and front will be converted to modern disk. I want the stock look and will only probably be running 13" wheels. Which are 4 1/2 -5" wide in rear 4" in front. It is a vega rear and that's one reason i wanted it was matching bolt pattern. My friend Jaks has one with a Suzuki engine & trans but when you see the wheels you can tell its not original drive train.
     
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  26. Desmodromic
    Joined: Sep 25, 2010
    Posts: 571

    Desmodromic
    Member

    Don't know how much power you're trying to accommodate, but a Sprite/Midget is 42" track, same wheel bolt pattern, good for maybe 3 to 4 times Crosley power. Triumph TR3 is 45" track, has 4.5" bolt circle. Virtually all other "findable" axles have at least a couple of inches wider track.
     
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  27. badvolvo
    Joined: Jul 25, 2011
    Posts: 471

    badvolvo
    Member

    Talk to your machinist about resplining the axles, by narrowing that much, you may be out of the hardened area. I made that mistake once, twisted those babies right off the axle with a very mild 355 and street tires.
     
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  28. If you are building a Crosley they commonly had the wheels and tires outside of the rear fenders. Like mine. Of course not always and tires under the body is a matter of personal taste. The reason I am saying this is that maybe you only want to narrow the rear enough to center the pinion. ;) DAEF049C-73E5-44A6-9DC5-61A72E40A354.jpeg
     
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  29. Joe H
    Joined: Feb 10, 2008
    Posts: 1,525

    Joe H
    Member

    To your question about driveline angles and offset pinion, I would think the offset side to side would work just as well as up and down in a normal situation. The driveshaft doesn't know the difference, all it knows is the angle at front matches the rear.
     
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  30. In theory a pinion offset can give you some parasitic drag. In application it is not going to be a real deal breaker.

    If I am cutting one down I usually try and center the pinion. The math is really pretty simple.

    Let us suppose that you are cutting a rear that the pinion is offset 2". The rear is 8" wider than you want so you are cutting 8" off of the total width. To keep it the same offset you simply cut 4" off of a side. But if you to move the pinion 2" say to the right you would then cut 6" off of the right side and 2" off of the left.

    @Mr48chev that 9" housing I have hanging on my wall is 39.625" flange to flange with the pinion centered. I cut it to fit a specific car. That project took a different direction so now I have a round back 9 with a centered pinion that is going to need new tubes if I ever use it. LOL

    You may note that if the punkin is visible from the rear that it will no longer be centered. So if that is an issue just leave the pinion offset and cut 4" from a side.

    Soooo many decisions. LOL
     
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