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Technical 1956 Chevy, broken axle. What to do?

Discussion in 'The Hokey Ass Message Board' started by midnightrider78, Oct 18, 2020.

  1. midnightrider78
    Joined: Oct 24, 2006
    Posts: 967

    midnightrider78
    Member

    So, last weekend the left side axle broke in my '56 Chevy 150. Although it was disappointing, it wasn't really shocking. I wasn't shocked because, although the car doesn't really bite/always spins for 50-75 feet "out of the hole", it is a little over 500hp/500 ft lbs thru a stock(other than the posi) rearend.

    I have several questions
    1) If stronger axles(1541?) would solve my problem, that would be great. Any chance of that being a sufficient fix?

    2) IF I can get by with just replacing the axles, what do I need to do to check out my posi center(since I have it apart anyway)?

    3) If stronger axles are not going to do the trick, do I have any GM options that will cost less than a few months mortgage payments? Any chance a 10 bolt would do? I believe a first gen Camaro is already the correct width.

    I don't race the car, but I do "clean the tires off" once or twice a month during nice weather.
     
    chevy57dude likes this.
  2. Put an egg under the gas pedal.
     
  3. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,736

    2OLD2FAST
    Member
    from illinois

    Modify your driving habits or keep replacing broken parts . If this was a 1956 axle , I'd say its held up well considering its 2020 ! That's 64 years of abuse , fatigue finally won ...
     
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  4. DDDenny
    Joined: Feb 6, 2015
    Posts: 13,785

    DDDenny
    Member
    from oregon

    Yep, that axle needed a well deserved rest!
    Sure, aftermarket axles (should) fix your axle issues but the next "weak link" will be the ring and pinion.
    I would say you have been extremely lucky, my 57 had a 283 and would snap axles and blow third members pretty regularly.
    Time to bite the bullet and swap in a 9 inch Ford rearend.
     

  5. finn
    Joined: Jan 25, 2006
    Posts: 688

    finn
    Member

    I’ll probably get a time out for this, but an 8.8” Explorer can be found with traction lock, disc brakes, and 31 spline axles.

    Cheaper than a 9”. Easier to find too.
     
  6. chevy57dude
    Joined: Dec 10, 2007
    Posts: 5,781

    chevy57dude
    Member

    Sorry, you can have NO expectation of a stock rear holding up to more than 300 HP.
    Not with any kind of traction. If you have a ''P'' case center section, sell it to a restorer and put the money toward something you can beat on. It's no fun having to baby a car because of a weak link.
     
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  7. rbrewer
    Joined: Mar 16, 2011
    Posts: 138

    rbrewer
    Member

    @chevy57dude is right, no need to destroy original parts, here are some reference material links below for maintaining original rears,
    "3) If stronger axles are not going to do the trick, do I have any GM options that will cost less than a few months mortgage payments? Any chance a 10 bolt would do? I believe a first gen Camaro is already the correct width."
    Lots of info on line about the 10 bolt 8.5 rears, ( try the tri five site,EATON etc) I have no experience with them, but they seem to have a good rep.
    If you do that, don;'t trash your stock rear.
    http://chevy.oldcarmanualproject.com/booklets/57top30/5730smindex.html
    https://www.chevytalk.org/fusionbb/showtopic.php?tid/223802/
     
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  8. squirrel
    Joined: Sep 23, 2004
    Posts: 46,872

    squirrel
    Member

    spend the bucks to put an Olds/Pontiac rear from the early 60s in the car.
     
    Gasser 57, dan c, gas pumper and 11 others like this.
  9. In the late 60's, a friend ran a 55 chevy "p" stocker. 265 corvette option and 3 speed trans. He started painting stripes down the axles to mark the twisting. The record was 8 turns before breaking. This was a 195 hp. engine with a Lunati cheater cam and 7" cheater slicks. I think it had 5.57 rear gears. I'm amazed that you made it this long. Maybe you should be buying lottery tickets. :)
     
  10. chevy57dude likes this.
  11. Mike VV
    Joined: Sep 28, 2010
    Posts: 2,061

    Mike VV
    Member
    from SoCal

    Yep, like squirrel says...

    Many many years ago, when I had my 56 Chevy sedan, and after breaking a couple of axles and a few spider gears, I installed a 57 Pontiac rear end (THAT's a long story!)...and as they say, never looked back. I had the Chevy axles all twisted and everything. As things go...not much to them really.

    I put in a cheap Pontiac assembly, and as money was good, I bought a Posi. unit, and a pair of 31 spline axles.
    Never had a rear end problem after that.
    Was plenty to go 13.00's at the original Irwindale Raceway. Never did run in the 12's with that car..!? Probably could have been in the 12's with better slicks, but that wasn't a particularly "plentiful" time in this young man's life..!

    Mike
     
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  12. jaracer
    Joined: Oct 4, 2008
    Posts: 501

    jaracer
    Member

    Those were pretty strong axles. I remember the dragsters using Olds rears in the late 50's, probably Garlits.
     
    chevy57dude likes this.
  13. saltflats
    Joined: Aug 14, 2007
    Posts: 10,315

    saltflats
    Member
    from Missouri

    Aftermarket axle.
    20170620_075717 (2).jpg
     
  14. midnightrider78
    Joined: Oct 24, 2006
    Posts: 967

    midnightrider78
    Member

    I have nothing against Fords(I own several), but it turns my stomach to think of a non-GM rear in the car. I know that is the cost effective way(I already have a couple 9"), but I just can't do it.
     
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  15. midnightrider78
    Joined: Oct 24, 2006
    Posts: 967

    midnightrider78
    Member

    That's what I was considering as the P case is out of a '62 Vette
     
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  16. chevy57dude
    Joined: Dec 10, 2007
    Posts: 5,781

    chevy57dude
    Member

    GM 12 bolt may be your answer then. They use a little less power to turn than a 9'' also.
     
  17. midnightrider78
    Joined: Oct 24, 2006
    Posts: 967

    midnightrider78
    Member

    That's one thing that was kind of surprising. These are the original '56 axles and the car was driven pretty hard in the early '70s, but the splines that I can see look great. It just broke the LH axle off as clean as if it were cut in a machine.
    I say "...splines that I can see..." because the stub of the LH axle is still in the posi as it is too short to grab and I haven't yet determined how to remove it.
     
  18. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,736

    2OLD2FAST
    Member
    from illinois

    When is the last time GM made a good rear ? Old/ Pontiac was a long time ago , wasnt it , Chev as well ...
     
  19. Most axles are undercut from the splines on a taper back towards the flange. That provides the torsional twist to avoid breaking the axle right at the spline intersection. We tried shortening axles without that. 1 or 2 runs would break them without the undercut.
     
  20. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,981

    olscrounger
    ALLIANCE MEMBER

    Years ago had a 56 with a strong 400 small block-broke the stock axles easily-put in a 12 bolt posi and never had an issue again.
    Wife's 55 has a 69 Camaro 12 posi as well for 30 years after tearing up stockers. Friend just was given a 70 Nova 3:55 12 bolt posi-told him hang onto it.
     
    Last edited: Oct 18, 2020
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  21. Mitchell Rish
    Joined: Jun 10, 2007
    Posts: 1,073

    Mitchell Rish
    Member
    from Houston MS

    57--59 pontiac/olds rear - problem solved.
     
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  22. RJP
    Joined: Oct 5, 2005
    Posts: 1,654

    RJP
    Member
    from PNW

    Dana 60.... You'll just have to do it once.
     
    Last edited: Oct 19, 2020
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  23. jimmy six
    Joined: Mar 21, 2006
    Posts: 7,139

    jimmy six
    Member

    The words Pontiac rear end and cheap no longer go together. Both my race cars have them and my son after finishing the now his 40 Chevrolet said, “do you know how much all those Pontiac pumpkins are worth” I said Yep.....way more than we paid for the 40 in 1974.
     
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  24. brigrat
    Joined: Nov 9, 2007
    Posts: 5,275

    brigrat
    Member
    from Wa.St.

    You will be forever chasing problems with a GM rear and your driving habits. Go a Ford 9" and be done with it. Besides that what are you doing running around with stock width '56 rear brake shoes & 500HP? You should already have upgraded the rear brakes and probably the front as well.............
     
  25. hemihotrod66
    Joined: May 5, 2019
    Posts: 230

    hemihotrod66
    Member

    Broke a few GM rearends and axles in my 55 Chevy...Left GM behind and went to Superatock Dodges...Never had any trouble with 8 and 3/4 dropout Dodge rear ends or axles...I prefer dropout rear gears so today it would be a 9 inch Ford from Mark Williams...Just my take...
     
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  26. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,882

    1971BB427
    Member
    from Oregon

    For those who want an inexpensive fix that will be much stronger, the 8.8" Ford is a great choice. They are available with drums in earlier years, and discs around 1994 on. And most salvage yards have plenty in 4.10, 3.73, and 3.56 posi that are dirt cheap. You can't buy good gears for a 9" Ford for what they sell a good 8.8" Ford posi for. And those who say go to a 12 bolt will be happy to know the 8.8" is just Ford's version of the 12 bolt. They're identical internally in design, and even use the same clutch packs for 31 spline axles. So if you can't get over having a Ford in your Chevy, just don't count how many differential cover bolts there are, and you'll be smiling at the money you save.
     
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  27. Budget36
    Joined: Nov 29, 2014
    Posts: 4,264

    Budget36
    Member

    I think many don’t want to go with the 8.8 due to BP differences. The cost of new wheels or redrilling axles will add up. Adapters are and option I guess, but are more maintenance
     
  28. midnightrider78
    Joined: Oct 24, 2006
    Posts: 967

    midnightrider78
    Member

    Have discs on the front and a better master cylinder. With the brake system 100% new pieces front to back it actually stops better than any other old car I have had.
     
    Last edited: Oct 18, 2020
  29. midnightrider78
    Joined: Oct 24, 2006
    Posts: 967

    midnightrider78
    Member

    I know a Ford rear is the economical way to go, but I just can't do it. I'm weird about stuff like that.

    I've wanted to do the 9.3 Pontiac rear for some time, but they look like a monster $ outlay... like 4k or more for the whole rear as I would like it.

    I've got a 12 bolt in the parts stash but it is a super wide(like 65" drum to drum) one wheel wonder.

    At least this happened when the driving season is basically over for this car.
     
  30. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,882

    1971BB427
    Member
    from Oregon

    Not sure what "BP differences" are? But considering I can buy 8.8" Ford posi all year for $200 at my pick and pull, I can easily pay the $100 to have axles redrilled, and still save. Adapters are OK too, and not sure how they require "maintenance"?
    I've used the 8.8" in my last 4 builds, and I'd never go with anything else. Especially if it's a new build and you haven't bought wheels yet. But even for a rework it's stronger, and a bog money saver.
     
    Tman, ffr1222k, bchctybob and 2 others like this.

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