8.75 rear in 71 swinger slant six car?

Transmission and Drivetrain Tech

  1. MoparMike1974

    MoparMike1974 Well-Known Member

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    Is this possible. I got a parts car and I never bothered looking under it until today. Much to my surprise its got an original A body 8 3/4 in it. 489 case, unknown gears, peg leg. Still has original flared drums and the install looks factory. If someone swapped this in they did it right and it was done a long time ago.
    I found half a build sheet and of course the part with the axle code is gone. So has anyone ever seen a factory 8 3/4 in a slant car?
    Is there axle info on the fender tag?
     
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    • Bodyperson

      Bodyperson A little sketchy

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      I bought a 72 part swinger with a slant and it had an 8.75. Don't know if it was original either. Mine is an X case
       
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      • Alaskan_TA

        Alaskan_TA Well-Known Member

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        Years ago I saw a 1970 Duster with a /6 & original 8 3/4"

        My 1970 Valiant 4-door with a 318 has one also.

        It is more of a gear ratio selection Vs. a HP application or not.
         
      • RSie

        RSie Idiot In Training

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        When I was 14 or so, my brother who was a mechanic got me a summer job working at the dealer washing new cars. I washed a brand new Dodge Aspen 4 door.. Dodge Aspen on the front... Plymouth Volare on the back. My brother wanted to buy the car.. the dealer made it into a Dodge. Oddball stuff coming out of Chrysler is the norm.
         
      • MoparMike1974

        MoparMike1974 Well-Known Member

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        Hmm, ok maybe it is original. No way to prove it unless there is another build sheet up under the dash. I looked everywhere else and even behind the glove box. Dash will probably be coming out this weekend but I dont expect to find another one.
         
      • RSie

        RSie Idiot In Training

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        Could have happened at the dealer too. Without build sheets you'll never know (and I have a suspicion those aren't always true). Whatever, ya got a 489 case 8 3/4 :)
         
      • George Jets

        George Jets 1967 Dart 2 Door FABO Gold Member

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        Just curious, what is the gear ratio on that 8 3/4, 3.23 ?

        Maybe 2.76.

        67 Dart had the 3.23 with a 170 slant.
        72 Duster with 225 slant had 2.76
        74 Dart with 225 slant had 2.76
        All had the 7 1/4s, but just for the ratio sake.

        If the 8 3/4 still has the ratio tag on the pumpkin bolt yet, that could be a clue as to it being original. If the ratio tag is missing then maybe someone swapped it in cause the
        7 1/4 was clunking ???
         
        Last edited: Aug 15, 2019
      • Dana67Dart

        Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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        I recall seeing that with a towing package you got a 8 3/4 , can't imagine that they would offer a towing package with a slant but you don't know
         
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        • Kern Dog

          Kern Dog Well-Known Member

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          It is true. The towing package included the 8 3/4" axle due to durability. I have seen many ho-hum cars come with the 8 3/4" axle. Keep in mind that by the end of the 1972 model year, they may have been stuffing them into anything just to use up the last of the inventory.
          I have seen these axles in several non performance cars. Last October I traded for an 8 3/4" axle that came from a 4 door 71 Valiant.
           
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          • MoparMike1974

            MoparMike1974 Well-Known Member

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            I dont know what the ratio. Its a one legger so I cant count the revolutions. Tag is missing so I wont know until I pull it.
             
          • mbaird

            mbaird mbaird FABO Gold Member

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            Yes. A /6 with tow pkg would have an 8.75.
            I got one with 3.23 suregrip out of a salvage yard car.
            Chock 1 wheel and turn the other to count pinion revs.
             
          • RustyRatRod

            RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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            Yes. Happened a good bit.
             
          • jos51700

            jos51700 Well-Known Member

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            My friend Chris's parents ordered a '71 Dart four door new with a 318 auto and special order 8 3/4".

            You could order them in anything!
             
          • mopardude318

            mopardude318 Well-Known Member

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            I’m the second owner of my 1970 Dart, it had a slant 6 with a tow package, and of course the 8 3/4 rear axle. I’ll try and find my build sheet, I put it somewhere 15 years ago, I gotta remember where. Lol.
             
          • MoparMike1974

            MoparMike1974 Well-Known Member

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            Where would the tow package be listed on the build sheet? Also, what did the tow package consist of besides the hitch?
             
          • Demonic

            Demonic Well-Known Member

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            IIRC, a 70 Dart or Valiant with a 318 and manual 3 speed on the floor had an 8 3/4 as standard.

            A tow package would have an aux. transmission cooler and I think 3.55 or 3.23 gears, and heavy duty cooling. No 2.94 or 2.76 ratio.
             
          • moparmarks

            moparmarks FABO Gold Member FABO Gold Member

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            Yep I parted a 71 Dart rubber floor mat car. /6 with 3 on the tree and an 8.75.
            A friend has a all original 72 Duster /6 w/ a/c, disc brakes and an 8.75.

            100 (10).JPG

            100 (11).JPG
             
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            • abodyjoe

              abodyjoe Well-Known Member

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              Yes slant six cars could be had with an 8 3/4. Have seen many over the years. 4 door slant cars too. Have seen slant cars with 8 3/4 rear, front disc and away bar.
               
            • R4Sedan

              R4Sedan Life in the Fastback Lane FABO Gold Member

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              Yep I have seen them also. And plenty of B-body 4-doors with them.
               
            • MoparMike1974

              MoparMike1974 Well-Known Member

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              This one does have power disc brakes.
              No oil cooler and standard 22" radiator.
               
            • 65 Dartman

              65 Dartman FABO Gold Member FABO Gold Member

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              Years ago I bought a 71 Valiant 4 door from the original owner who ordered it brand new.. he was going to do some towing with it so ordered the HD axle - 8.75 with 3.23 gears and a Sure Grip. For mileage he said he ordered it with a slant. Whatever!

              Edit: it had Kelsey Hayes discs as well
               
            • mbaird

              mbaird mbaird FABO Gold Member

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              Tow pkgs usually consisted of bigger radiator / fan shroud / 7 blade fans ( more blades) bigger axle and lower gears . Different applications may have varied.
               
            • Dartnut

              Dartnut Don't hate me because i'm beautiful

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              One thing that i learned years ago was to never take anything for granted when it comes to options on our Mopar cars.
              Keep in mind, the factory would allow an upgrade on a car to keep it going down the assembly line, but not a downgrade.
              There was a lot of weird combinations that make little sense other than someone special ordered it, or on the assembly line, that's all that was available at the time when the car was being built.
              I always never take anything for granted, always look at the car closely!
              Also, these cars are getting pretty old now, so anyone could have changed anything years ago and it would look like it was built that way from the factory.
              Repair shops were notorious for sourcing parts from junk yards and they didn't care if it was original, just as long as it fit and they got paid for the job.
               
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              • cojohnso

                cojohnso Well-Known Member

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                This likely or may have been built in Mexico. They were very bazaar. I saw a 77 Volare Superbee. (At least that was what they called it.) With a 360 4-barrel that was not emissions allowed in US. Thus it was fast by '77 standards. So strange was this Chrysler would not allow either Dodge or Plymouth badging. It was kinda combination of both. Of course I wanted it. But not sure if it could even be licensed in Minnesota.
                 
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                • mbaird

                  mbaird mbaird FABO Gold Member

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