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Technical 9” Ford /39 Chevy fit

Discussion in 'The Hokey Ass Message Board' started by The Bomber, Oct 17, 2021.

  1. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Anyone know if the 9” Ford leaf spring perches line up right underneath the stock leaf spring location on the frame? Thanks for any info…
     
  2. Really hard to answer the question based on the sparse information. Spring perch distances, WMS to WMS distance, and perch on top or bottom of the axle on a Ford 9" rear depend on what application is was built for. Typically most cars from that era need a WMS to WMS distance in the 56" range, and will probably require the spring perches to be moved inboard slightly. The 57-59 Ford is the narrowest one, but getting harder to find. If horsepower is 300 or less, you could opt for an 8" out of a 70s Maverick. WMS distance is 56.5". I have a couple right now, and could get the perch distance if you want. An 8.8 out of a Ranger is also worth looking into. Measure the distance between the springs on the car and either start hunting or have a custom rear built from a company such as Currie. A search of the archives will also help.
     
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 52,772

    squirrel
    Member

    I'd say 58" to 60" depending on what wheels you're going to use. Which is the first thing to figure out, of course.
     
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  4. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,800

    1971BB427
    Member
    from Oregon

    Even if they did match the width, the pinion angle might be wrong. Best to just cut them off and weld them where you want, with the correct pinion angle.
     
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  5. I measured the 3 rears I have. Spring perch c/c on a 76 Maverick is 43.5", with a WMS of 56.5". 1968 Cougar 8" (which also came in 9") is 43.5 " with a 58" WMS, and a 58 big Edsel is 42.5", with a 59" WMS. As mentioned, pinion angle and if it needs to be centered factors in.
     
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  6. vtx1800
    Joined: Oct 4, 2009
    Posts: 1,522

    vtx1800
    Member

    I used a nine inch out of a Cougar (late 70's ?) and it was too wide, note that axle has a long and short axle, I had a local shop narrow it to fit the short axle, moved the spring perches and welded it up. NOTE....make sure the axle has the loaded weight on it before welding up the perches....I had to put wedges in to get the proper pinion angle. I should have known better.
     
  7. i7083
    Joined: Jan 3, 2021
    Posts: 116

    i7083
    ALLIANCE MEMBER

    I cut mine to 60" in my '39. Depends on wheel backspacing, of course...
     
  8. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Sorry left out important info.. I have an 8” in there with spring pads on the bottom, planning on taking out the original old leaf springs, and getting a set of Posies, they have some that will bolt right up to the existing leaf spring frame mounts, they also come with the pin re centered , as I found out the hard way that the original Chevy pivot rear would throw you off about an inch from center, going to a open rear. The posies will lower it 3”, problem is the 8” rear has square tube that was welded on the perches to lower the car to begin with.I figured the two combined would be too low, so I figure if I’m going to take the 8” out why not go for a 9”. However , the car would have 300 HP max, even if that . thinking of a Chevy rear but I know parts are expensive plus they hold the axle with a C Clip which a lot of guys don’t like..guess I created a ball of wax…appreciate your input…
     
    Last edited: Oct 17, 2021
  9. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

     
  10. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,326

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @The Bomber
    Within the past year I went through this exercise with my ‘37 Chevy build. The ‘37 thru ‘39 share rear end dimensions and floor pans. I mention floor pans because the stock Chevy floor has a bearing on what the axle assembly needs to be to fit. If you have, or will be, or are willing to change the floor, it makes a difference.

    The stock WMS to WMS on ‘37/‘39 Chevys is 59”. But, the oem wheels are narrow rims and have little offset. Meaning that if 59” is utilized, the wheel width and offset are critical to fit within the stock fenders.

    I started off intending to use a 9”. Soon discovered the size of the differential area of the axle housing is a bit large to fit in the space allotted. Then there is the issue of pinion offset. The Chevy floor has a narrow driveshaft hump and the driveshaft needs to be pretty much centered to fit the “space allotted”. An 8” axle is a better fit in that respect, but still needs a near centered pinion.

    Ultimately, I built an 8.8” rear end assembly from parts. I discovered that Mustangs of the ‘89/‘93 era are 59” WMS. They also have equal length axle shafts and an almost centered pinion/driveshaft. Ranger pickups also used both 7.5” & 8.8” axle assemblies. Unlike the four lug mustang, the Rangers use the standard Ford 4.5” bolt pattern with 5 lugs. AND, the early Ranger long side axle is exactly the same length as the Mustang 4 lug. So, two stock 5 lug Ranger long side axles put me in bidness. By the way, Ranger 7.5” & 8.8” use exactly the same axle shafts.

    I had an abundance of axle assemblies on hand ….8”, 9”, 8.8” and 7.5”. The Mustang had disc brakes but I preferred drums on the rear and used the 10” Ranger drum setup. Because of the 59” width I had to be careful about wheel selection as mentioned above. I used 6” wheels as my engine is about 230 hp and I did not need, nor want, big rear tires.

    Now, what can you glean from all of this information. The key points are overall width, pinion offset and floor clearance around the differential area of the axle housing. With the 8.8”, which is comparable to the 9” diff size, I recessed the front of the trunk floor vertical ‘wall’ to clear the back of the diff housing.

    If you choose to modify the floor of your ’39, for driveshaft and/or diff clearance, you will have more options for axle selection.

    Ray
     
    Last edited: Oct 18, 2021
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  11. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Hey Ray I notice you’re from Quincy, IL. I’m from Quincy, Mass. lol…Wow! You have provided a wealth of knowledge here.thanks so much for your reply. I didn’t even think of the 8” being a better fit. Is the bearing you mentioned the little dip in the trunk floor that the spare sits in?.. after hearing the 8” is a better fit, I just may stick with the 8” already in the car..been using it for about 15 years driving everywhere.I know I sound like an idiot and you’re probably thinking , “ keep it, if it isn’t broke don’t fix it!” I thought going to a stronger rear, but I also have about 220-230 HP like yourself, I run 235r15’s on the back, you consider them too big? I would never run slicks….Also I have a 700r in front of it..I know what you mean by the trans tunnel. Pinion angle is also good..so after looking at rear ends maybe I should just go back to square one where I started, like I have done on a lot of things lol…why rock the boat? You opened my eyes on this stuff… however my rear is a 64-77 Maverick 8”, 5 lug. this is different than a 8.8 “ as in an explorer… correct? Please respond…the gears are around the 2.70-2.90 range maybe? I suppose I could go to 3:03 or 3:21’s , but, who knowsmileafe is good now. One thing I will do is call Posie’s and mention I have a lowering block on the car and mention the height at the bottom of the rear of the body..that way there he can advise to leave it or not with the slide springs. A friend of mine with a 39 runs the original leaf springs but had a few leaves removed to lower it . Don’t know if I should do that, they are after all ..old 39’s… but do you run originals? Thanks for any additional info on my reply..appreciate it… and yes, I agree about physics winning… the very thing that makes planes fly and creates engine vacuum I read..
     
    Last edited: Oct 17, 2021
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 52,772

    squirrel
    Member

    btw, when I built my 39 many years ago, I used a 79 Monte Carlo rear, which is a 7.5" ring gear. It fit pretty well, and worked with 6" wheels and 235/75 tires. I think the same rear was used on most GM mid size cars from 78-86. They might be getting harder to find these days. The 8.8 Ray used is a stronger rear, although it's not a Chevy bolt pattern for the wheels.
     
  13. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Yea Squirell i did look at the monte Carlos and others from those years, also the BUICK, OLDS,PONTIAC from then that had the bolt on axles opposed to the Chevies which had the Accor held in with c clips as you probably know..yea so many out there even thought some had same measurements…it can make your head spin, lol..hey thanks for the info squirrel. Appreciate it.
     
  14. squirrel
    Joined: Sep 23, 2004
    Posts: 52,772

    squirrel
    Member

    The 8.8 also uses C clips. They generally work just fine...
     
  15. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Oh that’s right..thought I read that about the explorers…guess it’s common practice otherwise they wouldn’t keep making them..thanks…BTW, I remember seeing Sierra Vista at night all lit up driving toward there from Tucson. Beautiful!
     
  16. Rusty J
    Joined: Nov 25, 2019
    Posts: 142

    Rusty J
    Member

    I'm building my car right now but using an explorer 8.8 with disc's on Chassis Engineering springs. Haven't set any angles yet but so far there's no clearance problems - but I'd recommend looking carefully at the wheel centering in the fenders because they're off from factory - too far forward, I'm moving my setup back 1 1/4" and slightly modified the fenders to better center the wheel visually (running 20 x 10 wheels) The wider wheel (luckily) had the perfect backspacing for this diff so it worked out perfectly for me.
     
  17. squirrel
    Joined: Sep 23, 2004
    Posts: 52,772

    squirrel
    Member

    spend some time on the wheel centering thing...if you stare at the wheel opening long enough, you'll see that it's "swept back" at the bottom. The front of the opening covers the tire a bit, by design. Make sure you find the center of the wheel opening radius, above the tire, and match that to the tire location.
     
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  18. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Yes I like many others learned the hard way about the axle having to be centered in the wheel wheel.Found out that the original 39 rear pivoted, and because the setup was different than and open drive..all you had to do was drill a hole 1-1/4 which re located the pin on the leaf spring to center..wish I knew then..I see quite a few off center..who knew? Lol..thanks.
     
  19. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Yes I learned the hard way lol thanks
     
  20. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,326

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Glad you found my comments useful. I have to back track slightly….upon further recollection, I remembered that my first intent was a Ranger 8.8” with 58.5” WMS measurement. However the pinion offset was pretty severe in addition to the size of the diff compared to stock Chevy. So then I began to assess the 8” & 9”. While the 8” is a better fit in the diff area, they have limited factory ratio availability.

    At that point my options were to narrow an 8” or 9” housing and buy new axles of the required length. There are both 8” & 9” stock axles of suitable width, but they are difficult to come by used. Buying a new housing and axles is pretty expensive. Eventually that is what led me to the ‘home build of compatible used parts described in my first post. Use parts were the housing, brake backing plates, limited slip differential carrier and 3.73 gear set. I replaced all bearings, rebuilt the locking diff and brakes.

    @squirrel makes a good point about the GM 10 bolt (typically 7.5” in GM intermediates). They are certainly adequate for under 300 hp. A good friend has one in his ‘37 Chevy and it has served him well for more than 20:years. The midsize/intermediate GM from’78 thru whenever are about 58” WMS/WMS.

    My comments about tire size merely was cautionary about exceeding the available space in the stock wheel housing/fender area. If your 235/15 work in your application, obviously they are not too big.

    Your rear axle ratio seems a bit high (low numerically) for and OD transmission. An engine with high torque in a light weight vehicle can handle low numeric axle ratios, but with a 700R4 in your ‘39 would probably benefit from at least a 3.30 ish, better yet 3.50 ish and could easily handle a 3.73. The 700R4 does have a super low 1st gear, 3.06, that compensates for a tall rear axle ratio on initial acceleration, but is not so suitable for highway cruising, especially in rolling terrain.

    By the way, I used a replacement rear suspension kit, I believe it is TCI, but bought from Speedway. It has fewer leaves, but wider, and included all new spring mounts and shackles, tubular shocks and a crossmember for the chassis to attach the upper shock mounts. Although the springs were ‘flatter’ than the stock springs and did lower the car some, I added lowering blocks of about 1.5” as I recall. That still left me with a reasonable amount of axle travel before bottoming out.

    Ray
     
    Last edited: Oct 19, 2021
  21. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Again Ray, thank you for all your latest information.like anything else, quite a lot of things come into play getting different things to fit and consider.Even with the 700r and the 2.79 gear ratio, the car has been very good on the highway, hills and all , responds well and gets great mileage..so, I guess I can’t complain. Thanks for taking the time to write your reply.I know it was a lot of typing but is is a wealth of knowledge and experience..very well appreciated. It will be a great reference..take care from one Quincy guy to another Quincy guy.
     
  22. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,326

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @The Bomber

    In your town it is Quinzee…..here is it is Quinsee…:D

    I was there once, many years ago…..1981 to be exact. Airline layover due to the Air Controllers Strike. Went to Quincy Farmers Market….Faneuil Hall as I recall……great and fun experience!

    Ray
     
  23. The Bomber
    Joined: Dec 10, 2005
    Posts: 547

    The Bomber
    Member
    from mass.

    Lol yes our lazy Boston type accent pronounced it Quinzee..I suppose you heard it like that a bit just walking around Quincy Farmers Market..glad you had fun.
     
    Last edited: Oct 18, 2021
  24. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,800

    1971BB427
    Member
    from Oregon

    I moved my rear axle back about 1.5" by simply disassembling the leaf spring packs and drilling the main leaf center pin hole 1.5" back, and then putting the other leafs back together on it. I also wanted to lower the rear a lot, so I tossed the old '39 leafs and replaced them with an assortment I put together from '55-'59 Chevy pickup front leaf springs. They're flatter, and thicker, so they take fewer to get the spring rate.
    I still had to add a 1" box tube riser welded to my spring perches to lower it another 1" and get the stance where I wanted it. I'm using the same 8.8" Ford mentioned, and mine is from an Explorer with drum brakes. I contemplated disc brakes, but since I had this axle sitting here I figured I'd just use it as is.
    My '39 coupe sat way up in the rear, and had the 9" Ford axle above the springs. I'd have used the 9", but it was a 3.08 open differential, and I wanted the 3.73 limited slip the 8.8" had.

    [​IMG]

    This was taken during mockup.

    [​IMG]

    This was the box spacer I welded on the perch to lower it more.

    [​IMG]

    After centering it, and adding the spacer to the perches.

    [​IMG]

    [​IMG]
     
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