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Technical Help with Rear end ID

Discussion in 'The Hokey Ass Message Board' started by abe lugo, May 30, 2019.

  1. I bought a new-to-me car, Its a '41 Cadillac. It a nice old car but has a few things to fix.
    The drive train was updated to a 472/500 Cad motor.
    I have yet to learn about them and figure out how to ID the engine.
    I actually want to go back to a Flathead, but this will suffice until a good donor is found.

    One thing that I did notice is the rear was changed also.
    See image, I figure its a 13 or 14 bolt cover. I'll have to feel it up tomorrow and get an actual count.
    Any help ID this would help me sort out the brakes. I have not popped off the rear wheel covers yet to see what the Bolt circle it. I'll check tomorrow.
    And yes there is some hokey welding on some mounts and stuff like that, it will be gone through.

    0311191251c.jpg
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 55,942

    squirrel
    Member

    12 bolt Chevy...you'll need more details to get it identified the rest of the way.
     
  3. DFC3666A-35B9-4207-B291-0CD60B720287.jpeg That is what it thought thanks Squirrel. I’ll get more info ASAP. I didn’t check for tag with the ratio on. Just got the car yesterday. It’s has a bad master cylinder setup. But somehow stops. I don’t want to rely on it without knowing works well all around. It’s a heavy car.

    By the end of the week there will be a laundry list of things to check, document and put in the list for fixing.
     
    kidcampbell71 and 40LUV like this.
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 55,942

    squirrel
    Member

    If you can get a good idea of what brackets on the rear might be original, they can help with ID. The 12 bolt was used in mid and full size cars with 4-3/4 bolt circle from 65-72(?), and full size cars with 5" bolt circle from 71-75ish. Also used in trucks with 6 lug wheels 63-70, and with 5 lug 5" bolt circle from 71-81ish. Cars and trucks used different suspensions for different models and years, some had upper mounting lugs for control arms, or panhard bars, some had leaf springs.

    Truck 12 bolts used different gear sets, with different size pinion bearings, compared to cars.
     
    abe lugo likes this.

  5. Ericnova72
    Joined: May 1, 2007
    Posts: 595

    Ericnova72
    Member
    from Michigan

    With all due respect to Squirrel...I don't think it is either of the 12 bolt Chevy rears, car or truck. Bolt locations in the cover, and what appears to be an almost centered ring gear location and a very large pinion offset have me thinking this is the 12-Bolt Oddball 8.875" rear used in some of the biggest mid-70's GM full size like the Cadillacs, Olds 88 and 98, Buick Electra 225 and 335 from about 1972-1976 time frame.
    Doesn't share much of anything with the 12-bolt Chevy Car or Truck 8.875" 12-bolts, and parts like gear sets or posi units are nearly un-obtainable.

    The more I look at the picture, the more I don't think the big car 12-bolt or the 1977-84 8.75" "P" axle are right either. That huge pinion offset, centered ring gear, and what appears to be a bolt in pinion retainer all point to some other application.
    If it is 12-bolt Truck the camera angle is making it look very odd.
     
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  6. boltupal
    Joined: Dec 27, 2010
    Posts: 293

    boltupal
    Member
    from western ny

    Looks like a 1971 thru 1976 G.M. 12 bolt 8 7/8ths rear end. The olds and buick versions used bolt in axles .
     
  7. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Possibly from Cadillac ‘Commercial’ Chassis...i e......hearse/ambulance chassis....that could have been a donor car for the whole drivetrain. The Commercial chassis used some really heavy duty axles over the years.
     
    Last edited: May 30, 2019
    big duece likes this.
  8. boltupal
    Joined: Dec 27, 2010
    Posts: 293

    boltupal
    Member
    from western ny

    Nope i,m wrong Its not that. In 1970 you could get a extra heavy duty rear end in buick and oldsmobile full sized wagon. It looked alot like the 1970s cadillac rear end. Wagons were leaf sprung, the caddys were coil. Either way they are strong but no performance gears availible.
     
  9. squirrel
    Joined: Sep 23, 2004
    Posts: 55,942

    squirrel
    Member

    I expect you're right. It's been a long time since I messed with one of those!
     
  10. Thanks guys, I have old notebook from the PO and it does say the drive train was from an ambulance in one of the notes. I'll have to recheck. It hard to get under this car but I'll try to tonight to get better images.

    Since the original style shocks are gone, they added some funky mounts, you will see them in the pics. They upgraded to tube style from the lever shocks

    also there is stock panhard bar from the original rear, it was attached to this rear.
    They also mounted a fuel pump. near the new gas tank.
    A lot of this welding/brackets is not pretty but is been that way for 20+ years.
    There is also a funny mount on the top of the pass side axle, I have seen the other side of it, it looks like a mount on the previous car it was on.

    I suspect, they kept the original leafs and mounts as the mount didnt have lower shock mounts, so they weld on some of their own.

    0311191251.jpg 0311191251a.jpg 0311191252.jpg 0311191252a.jpg
     
    Last edited: May 30, 2019
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 55,942

    squirrel
    Member

    you might want to hold the camera back a bit so we can see the whole rear end, and also get a picture from the front.

    Most car ambulances were Cadillac or Oldsmobile commercial chassis, in the era that that rear end was used
     
  12. Beanscoot
    Joined: May 14, 2008
    Posts: 3,055

    Beanscoot
    Member

    I think I'd put a proper fuel pump on the engine itself and ditch the electric one.
     
    abe lugo likes this.
  13. Here some more pics
    The funky mount in the top it one of the original
    Trailing arm Link mounts. Looks like the one of the driver side was removed. Drum size is 13.5”
    It’s hard to get a good width measurement but right around 59” at the backing plate mount
    AA1D0B63-EDF1-432C-89A5-9920107AB69E.jpeg 8FF60C26-14EE-445F-91FD-BE0C79E22121.jpeg 37E487C9-2B72-479B-851E-0A74CE37F844.jpeg 88343268-56C1-44AB-A524-CB5486854F9C.jpeg 5C87A9C6-DB52-49AE-B45D-042A212392B7.jpeg B268B150-DA59-4623-9843-E463FF3390DE.jpeg 9496D6A6-7CE3-4F42-A2F0-2EAD32C4C191.jpeg 283D30FF-647F-4A2F-8248-AFB436D8A810.jpeg
     
    Last edited: May 31, 2019

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