A-body 8 3/4 rear end swap into F-body

Transmissions and Rear Ends

  1. biomedtechguy

    biomedtechguy Member

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    I had a new 79 Aspen R/T E58 police 360 back in 79, 8.25 2.72 gear SureGrip.
    My 8.25 axle was damaged when I slid into a curb. I bought a 73 340 4 speed Dart from a junkyard and swapped in the 8 3/4 rear end from the Dart into the Aspen.
    Everything swapped over as an assembly, even the pins on the perches lined up with the holes in the leaf springs! It was a DIRECT bolt in swap! Shocks, brakes, etc all lined up and swapped over to the 8 3/4 like it was made for it.
     
  2. Kernel Sanders

    Kernel Sanders Well-Known Member

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    Wasn't the bolt pattern wrong? Abody (if original) 5x4" bolt pattern (SBP) and your Fbody 8.25 should have had a 5x4.5" bolt pattern (LBP)

    ...thinking about it more... 73 Abody wouldn't have an 8.75 from the factory. 8.25 or 7.25 only IIRC
     
  3. Dr Lebaron

    Dr Lebaron Well-Known Member

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    And isn't width off on a 'A' axel?
    Everyone I know use 1965 to 1970 B-body 8 3/4" rear axle, as it is the closest fit to the F/J/M platform because the spring perch centers are 44" compared to F/J/M bodies 44.46".
     
  4. Greg55_99

    Greg55_99 Well-Known Member

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    I can confirm that about the B body axle because that's what I have in my car.
     
  5. biomedtechguy

    biomedtechguy Member

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    I am absolutely certain that the 73 340 4 speed Dodge Dart 8 3/4 went in to my 79 Aspen R/T because I removed the 8.25 assembly, removed the 8 3/4 from the A body Dart, and installed it in my Aspen all myself, maybe with a little lifting help. I was especially happy that the spring perch pins lined up perfectly with the leaf springs.
     
  6. MiradaMegacab

    MiradaMegacab Well-Known Member

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    A body spring perches are 43"
     
  7. BudW

    BudW Moderator Staff Member

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    It is very possible someone replaced the ’73’s 7¼” or 8¼” with an earlier year 8¾” assembly (I would if I needed to replace either one, in an A-body).

    Some mostly complete data I have compiled:
    REA data 1.JPG
    REA data 2.JPG
     
  8. MiradaMegacab

    MiradaMegacab Well-Known Member

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    Shorter drive shaft required for this swap too...............
     
  9. biomedtechguy

    biomedtechguy Member

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    Maybe it was a 72, I will check with my buddy who helped me out.
    It was a great, easy, cheap swap that allowed me to drive from Louisiana to St. Louis and back.
    The St. Louis event in 82 was 3 Chrysler car clubs all meeting at the same time: The National Street Hemi Owners Association, The Mopar Muscle Club, and the T/A Challenger / AAR Cuda club....it...was...AWESOME!
     
  10. Kernel Sanders

    Kernel Sanders Well-Known Member

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    ALL factory ABody rears are/were small bolt pattern. As Bud mentioned (great charts BTW!) the Abody you got the rear from had likely been replaced by the PO from an early BBody 8.75 with large bolt pattern. The perch difference 44" (Bbody) and 44.5" (FBody) it would just drop in easily for a matter of 1/4 per side wouldn't stress the bushings at all nor affect anything else adversely IMHO
     
  11. 80mirada

    80mirada Well-Known Member

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    73-76 A-bodies used 8.25" rears with a 4.5"x5 bolt pattern.
     
  12. BudW

    BudW Moderator Staff Member

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    The last 3, 4 or 5 years of A-bodies were the bigger bolt pattern that Chrysler vehicles used.

    Even the brake rotors on those last couple year A-bodies are the same as our FMJ-bodies.
     
  13. MiradaMegacab

    MiradaMegacab Well-Known Member

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    "When a E58 79 Aspen R/T with a 73 8 3/4" rear end hits 88MPH, you're gonna see some serious shit!"
     
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  14. BudW

    BudW Moderator Staff Member

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    I don’t recall ever seeing an 8¾” A-body differential with the big bolt pattern wheels.
    There might be some out there – but I don’t recall seeing any.
    8¼” axle shafts will not interchange with an 8¾”.

    I guess it is possible to shoehorn a B-Body diff into an A-Body.
    BudW
     
  15. F body Deconstructor Jim

    F body Deconstructor Jim Well-Known Member

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    Only the disc brakes were large bolt pattern from model year 73 on. All A body drum brake cars were small bolt pattern (5 on 4") right through the end of the run. Of course the 4 wheel drums went away as of 1/1/76 production. All disc from then on.
    The 8.75 rear was replaced with the 8.25 for the 73 model year. No A body 8.75 rears came with 5 on 4.5" from the factory and no 8.25 rears came with 5 on 4".
     
  16. biomedtechguy

    biomedtechguy Member

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    Well, this additional tid bit will bring some more comments I'm sure:
    When we drove my car to St.Louis, I put the Centerlines from my buddy's 70 Roadrunner on my car, and that was after the rear end swap....so I'm sure that I had the aluminum R/T factory wheels on my car. I also had tried out some Centerlines from another friends's fastback 70 Mustang. He had a 429 4v in the Mustang that he pulled from another friend's Ford station wagon-we used to call "the Raggin' Wagon" We had some fun riding around in that 429 powered 4 bbl wagon!
    This 8 3/4 was just a car in a junkyard that I picked out because I guess I measured the distance between the leaf springs and it had s SureGrip. I got lucky I guess, same with the Charger 8 3/4 chunk swap-but I did have to get that "adapted" U-joint, and I think I got the drive shaft cut and balanced.
     
  17. biomedtechguy

    biomedtechguy Member

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    Lol. Are you saying that something bad should have happened?
    I find it hard to believe, or I just was incredibly lucky, to have:
    1: found a 73 Dart Sport 4 speed that had a 340 (vs a 360) in it...I know 73s had both, early in 73 they had 340s, later in 73 they had 360
    2: the one that I found had some kind of other factory 8 3/4 parts swapped in?
    Am I misunderstanding something? I thought (think) that all 340/360 V8 4 bbl A bodies had a 8 3/4. As a matter of fact, my friend who helped me swap the 8 3/4 from the Dart into the Aspen just sold an ORIGINAL 72 Demon, and it had an 8 3/4
    o_O As far as the bolt pattern for the wheels, I know I put my aluminum Aspen R/T factory wheels on the 8 3/4 from the 73 Dart, and the 70 Roadrunner Centerlines and the 70 Mustang Centerlines too. Maybe I had adapters?? That is one detail (adapters) that I don't remember.
     
  18. biomedtechguy

    biomedtechguy Member

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    By the way, here is a picture of my current ride. 20161211_161249.jpg 20161022_133059.jpg
     
  19. biomedtechguy

    biomedtechguy Member

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    When they were new, I used to see a LOT of Dodge Daytona z cars...now I hardly EVER see them. I saw a couple at the Mopar Nationals in Columbus OH this year, and I have seen a couple tube chassis ones at the track, but I don't see any at car shows, same for the Shelby Chargers. Did they have unusually serious rust problems? or are parts to keep them going/restore them really hard to find?
    I would think that the "tuner" crowd would like to modify them. I did have a Mitsu/Chrysler Conquest TSi back in 2008. I liked the rear wheel drive. I did some mods to it and was running 14.3s in the quarter mile at 97 mph.
    Same question about F bodies. Why so few Roadrunner and R/T F bodies? I really liked mine, and to me, they were visually very much like the Dart/Demon/Duster body size/style. The 79 just by coincidence was my favorite grille and tail light design, I didn't like the 80 square grill, and the older F body tail lights didn't look as good to me, just my preference, of course.
     
    Last edited: Dec 17, 2016
  20. 7T8 Custom

    7T8 Custom Well-Known Member

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    I always preferred the 78 grille and tail light combo with the yellow for the turn signal in the tail light . But then I might be slightly biased.