Which rear end to use?

Transmission and Drivetrain Tech

  1. dazedand confused

    dazedand confused Well-Known Member

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    I have a complete 8-1/4 rear with large bolt patteren peg leg with high gears that cam out of an 65 plymouth barracuda.i was planning on having it rebuilt / modified posi with 3:55. I found an 8-3/4 rear out of 1967 coronet thats missing the guts and axle shafts. Which is cheaper to fix up? I know the 8-3/4 is stronger but? I'm dropping in a modified 360 under 400 hp with full manual valvebody 727 automatic . The cars unbody and suspension will be beefed up . Its my 65 dart I'm working on. Thanks for any help you guys can give me
     
  2. RustyRatRod

    RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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    If the 8.75 is stronger,you caint prove it by me. I think they are neck and neck. Also, with all you've mentioned, I believe the 8.25 will be the most economical choice. Remember though, you will likely have to find another carrier, as the 8.25 has a carrier gear split. So make sure you get the correct carrier for your gear set.
     
  3. toolmanmike

    toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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    65 Barracuda either came with a 7 1/4 or a 8 3/4. Obviously the 8 1/4 you have was not the original rear end. Sorry, I was just thinking outloud.
     
  4. jas0162

    jas0162 Well-Known Member

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    As far as I know the only carrier split with the 8 1/4 are the ones that use the 2.45 ratio. If yours has that ratio I think you are stuck with that gear unless someone makes a spacer for it. If it has a 2.76 or higher you should be good. The 8 1/4 is a good one, they used it in C bodys and full sized trucks... they will take abuse for sure.
     
  5. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    8-1/4
     
  6. 318willrun

    318willrun Utube channel 318willrun

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    but, I think RRR was suggesting if it is the 2.45 carrier, just get a different carrier from '95 on down Dakota, or some other 8 1/4 rear with a 3.21 or 3.55 and put that in the rear end housing, correct?
     
  7. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    That would be the way I’d go about it. 2:45’s out, entirely, swap in sure grip and new gears all together. BAMM!
     
  8. jas0162

    jas0162 Well-Known Member

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    Maybe I didn't say that right. Im pretty sure that the ones with the 2.45 ratio cannot except any other ratio because the housing is cast differently. They moved the pinion away from the ring gear to make room for the huge pinion gear. The ring gear carrier itself I believe will interchange barring any axle spline differences... maybe that was what RRR was referring to. I didn't mean to complicate things
     
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    • halifaxhops

      halifaxhops It's going to get stupid around here! FABO Gold Member

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      The 8 1/4 should be fine in your application, you can get a sure grip and usually 3.55 gears from a jeep dana 35. The carrier is different not the housing with the gear split. We beat this topic to death in this thread has a ton of info in it.
      The 8 1/4 thread
       
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      • omahamoparguy

        omahamoparguy Well-Known Member

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        8 3/4 is expensive to build a strong version. 8 1/4 is way more common because of the variety of vehicles it was used in. [jeeps etc.] So it has support from the 4wd community. That makes it easier to build. Still it has the C clips but they dont seem to be troublesome like the gm C clip axles.
         
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        • halifaxhops

          halifaxhops It's going to get stupid around here! FABO Gold Member

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          I always shim the c clips so there is no lateral play, basically have to because I have rear disk brakes and if not during turns the axels shift in and out and make the pads rub on the rotors.
           
        • QuickDart360

          QuickDart360 Well-Known Member

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          8 1/4 will hold up fine. Just needs suregrip and 3.55's or 3.91's to really have some fun!!!:steering:
           
        • TrailBeast

          TrailBeast AKA Mopars4us on Youtube

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          I cruise all these posts and look for little pieces of gold, and that is a nugget worth keeping.
          Thank you.
          I'll be swapping to an 8 1/4 with discs from a Grand Cherokee as soon as I can.
          Probably get it this winter and have it ready to go when spring comes around.
          I'm considering the Powertrax product with 3:55 gears over the Suregrip since it would be easy to swap back and forth between a full locker and an open if needed.

          powertrax.jpg
           
        • QuickDart360

          QuickDart360 Well-Known Member

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          Is the powertrax durable? Since some time back someone told me the chrysler trac loc was not very reliable. Although the powertrax is different in design does look rugged. I went with the auburn gear suregrip unit. Auburn too gets mixed reviews!
           
        • daliant

          daliant Befuddled

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          The lock right locker is a pretty noisy unit, I have one in my daily driver Cummins powered Dodge W250. As far as being strong, it's held up so far and I don't baby it. It seemed to take a while to "wear in" where it would unlock quite often going around a corner. After about 500 miles it has calmed down a bit but still unlocks occasionally going around a corner. One time it must have unlocked both sides at once because it clanked so loud I thought I broke something, I had to jack the truck up when I got home to make sure one of the axles wasn't snapped in half.
          Oh and with 3.55 gears in a dana 70 I had to pull the carrier and take the ring gear off to install locker unit, it wouldn't clear the ring gear going into the differential.
          I think for the money one of those locker costs I'd just put some type of limited slip differential in it, they're a little more street friendly.
           
        • QuickDart360

          QuickDart360 Well-Known Member

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          Cool!! Good to know. I guess i did good with the auburn gear.
           
        • TrailBeast

          TrailBeast AKA Mopars4us on Youtube

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          Apparently since the redesign a lot of the drivability issue's have been worked out so they are quieter, but a lot of the posts I read on Jeep forums some of them are pushing 400hp through them.
          I guess a person would have to accept some of the oddities of it to run one.
          Plus you know the marketing isn't going to tell the absolute truth or they wouldn't sell them.:D


          Depending on what a limited slip costs in your area you may very well be right.
          Is your locker the original style, or the updated supposedly "improved" design?
           
        • sireland67

          sireland67 FABO Gold Member FABO Gold Member

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          I have lock rites in my old jeep because they are the only thing available.
          They clang bang clunk all the time.
          I put them in both axles, big mistake it make a 4x4 basically super hard to stear, but will go anywhere.
           
        • daliant

          daliant Befuddled

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          I don't remember which style it was, it's been a couple years since I put it in.
           
        • TrailBeast

          TrailBeast AKA Mopars4us on Youtube

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          Oh, ok thanks
           
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