Clamshell rear axle swap questions

Discussion in 'General Station Wagon Discussions' started by ClamWagon, Feb 20, 2023.

  1. ClamWagon

    ClamWagon Member

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    I have a 76 Olds Custom Cruiser that I am LS swapping CORRECTLY and will be perfect once done in a month. Does anyone know if this rear axle is the same/ interchangeable between all big body 71-76 GM cars or do wagons have different axles? I know in the 91-96 B body GM cars (impalas/caprice, roadmasters, fleetwoods), a sedan and wagon axle are not interchangeable.

    With such little information on the clams, I’m tapping into the Donk world for possible answers by basing axle swap info off of the 71-76 caprice classics that have been LS swapped which switch out facory axles for 95-96 Impala SS axles for better gear ration with posi, disk brakes and a stronger rear end.
    Any insight would be appreciated since I’m trying to have axle in possession and rebuilt before pulling factory axle out so car isn’t down for a while.

    chase
     
  2. KevinVarnes

    KevinVarnes Well-Known Member

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    Clamshell wagon rear suspension is leaf spring versus coils for the sedan so you will likely have to cut and weld old brackets from the donor. I have no idea if the track width is the same between the wagon and sedan. I believe that is the main difference with the later model (91-96) B-Body rear ends (width).
     
  3. elB

    elB Well-Known Member

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    The '71-76 big wagons are all the same axles I believe, but they are leaf spring as noted and without cutting and welding brackets a sedan\coupe axle won't install. It's not exactly rocket science to make it work, I've seen it done a few times over the years. The '71-76 wagon rears are downright indestructible in most applications, so I don't see a reason why you'd feel the need to swap one out for a '95-96 Impala SS one if the one you have is in good shape. The widths between the 2 are definitely different, not sure if it's different enough that you can't make it work as loads of dudes talk about having done it in the donk world on the sedans.

    Wagon rear ratios were in the 2.93-3.08-3.23 range for almost all applications (2.56-2.73 were listed earlier on in base engine\no AC models), with 3.42 and 3.73 allegedly available special order in '71-72 (maybe later). I have never seen one but that doesn't mean they don't exist, good luck finding one regardless.
     
  4. ClamWagon

    ClamWagon Member

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    @KevinVarnes @elB
    I honestly didn’t think about the leaf/coil issue! The gearing will definitely need to be changed, but if the axle is stout enough to hold some “ modest“ power, then maybe I can just have it re-geared. My concern was/is I would be devastated if I broken a snap ring and had the wheel and axle walk out contacting original wheel skirt/wheel well causing damage. That’s the only reason I have started to dig into options to solve that possibility since it doesn’t take much for me to find an excuse to do burnouts…
     
  5. Silvertwinkiehobo

    Silvertwinkiehobo "Everything that breaks starts with 'F.'"

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    There are C-clip eliminator kits for various rear axles with that style differential, as well as limited-slip units that can split the power if you get froggy on the go pedal.
     
  6. Brad

    Brad Moderator Staff Member Moderator

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    The "C" body wagons from 1971-76 use a 9 3/8" axle same as the rest of the rest of the "C" bodies, the only difference being the perches for the leaf springs vs coil springs. The biggest issue with them is the lack of support for most if not all wear items upto and including gears. There are NO aftermarket gears available for the 9 3/8" axle's and darn few maintenance repair items.

    My recommendation would be to go to a 8.5" corporate rear where gears and just about everything else is readily available in the aftermarket world. Get a 8.5" axle from 1971-'76 GM full size (B or C body with the 350 cid engine), swap your spring mounts and slide it in. The 8.5" is a very strong rear and will support your LSX engine easily.
     
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  7. ClamWagon

    ClamWagon Member

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    @Brad
    Great advice, I’m on the hunt now. Thank you!
     
  8. SwannyMotorsports

    SwannyMotorsports Well-Known Member

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    Find yourself a good 12 bolt rearend out of a 71-76 wagon that has bolt in axles. Then you need to find a 73-74 Buick Riveria GS 12 bolt rearend as they came with a 3:23 or 3:42 gear.

    The 12 bolts in these cars are very strong. Unfortunately no one makes the right size gears for them so there isn’t a lot of options.

    If you really want to build a bullet proof rearend with lots of gear options build a Ford 9 inch
     

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