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Technical Is there a difference between 55 chevy truck and car rears

Discussion in 'The Hokey Ass Message Board' started by RUSS BUCKLIN, Sep 16, 2020.

  1. RUSS BUCKLIN
    Joined: Sep 18, 2017
    Posts: 143

    RUSS BUCKLIN
    Member
    from Seattle

    So, like the title says, is there a difference between a 55 chvy car rear axle housing and a 55 chevy car rear axle housing? I have a 55 truck rear that will go into a 50 car with a 6 lug to 5 lug conversion (or redrill of the hubs if possible) if the housings are the same.

    Thanks
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 47,470

    squirrel
    Member

    they're different...the truck rear is heavier duty, the center section is round instead of oval. Would it work? Probably, but it's not what I would do, without a very good reason.
     
  3. jimmy six
    Joined: Mar 21, 2006
    Posts: 7,980

    jimmy six
    Member

    Just because you have something doesn’t mean you should use it. They have lower gears and can be made to fit a pre 55 car like Jim says it’s not a wise choice.
     
    Tman likes this.
  4. Russ,
    I have a '55 car rear axle I can sell you inexpensively. I can't really tell you anything about it as it came in a batch of parts I purchased, and it was not my priority.

    Scott (West Seattle)
     
    5window and squirrel like this.

  5. RUSS BUCKLIN
    Joined: Sep 18, 2017
    Posts: 143

    RUSS BUCKLIN
    Member
    from Seattle

    Scott, Sounds great, sent you a PM.
     
  6. Truck is six hole pattern, car is 5 hole pattern
     
  7. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,151

    Mr48chev
    ALLIANCE MEMBER

    Way too many differences to list. Along with 6 lug, the truck axles use C clips rather than being held in by the bearing retainer. Gear ratios are usually 4.11 or steeper yet.

    55 Car is traditional to put under those but 70's Nova size car rears work real well under those older Chevys. As will S-10 4x4 rear axles.


    No matter what you use you want a pair of these spring pad/axle mounts that not only locate the axle correctly in the wheel well they compensate for the difference in height so you don't get that jacked up in the rear look you get using regular spring pads like Moroso. These are truck but are the same as car https://www.classicparts.com/1947-54-Weld-On-Rear-Axle-Seats/productinfo/93-317/
     
    tb33anda3rd likes this.
  8. RUSS BUCKLIN
    Joined: Sep 18, 2017
    Posts: 143

    RUSS BUCKLIN
    Member
    from Seattle

    Thanks everyone. I just located an S10, 4x4 disk brake posi rear locally at a decent price so going to go with that, assuming everything measures out correctly.
     
  9. RUSS BUCKLIN
    Joined: Sep 18, 2017
    Posts: 143

    RUSS BUCKLIN
    Member
    from Seattle

    So, I got the S10 rear, 373 posi with disks. I have a question about the measurements. The S10 rear measures 60in WMS to WMS but the backing plate to backing plate distance is several inches narrower than the original. After I install the spring perches to their correct 45in centers it looks like it's a very tight fit for the leafs to fit inside the ebrake brackets. Observation/comments/experience with this install? Is this a problem I will need to address or does it all fit together in the end?

    Thanks and apologies if this is a dumb question.
     
  10. To your first question and the naysayers there is a historical precedent 57 Chevy Black Widows Grand National cars used the Six lug truck rear and front hubs.
    upload_2020-9-23_18-17-48.png

    Note rear cover and six lug wheels
    upload_2020-9-23_18-19-10.png

    upload_2020-9-23_17-55-13.png upload_2020-9-23_18-6-53.png
     
    swade41, tb33anda3rd and 6-bangertim like this.
  11. jimmy six
    Joined: Mar 21, 2006
    Posts: 7,980

    jimmy six
    Member

    True because the car ones were POS and couldn’t hold up. Especially the 7/16” fine studs. 6 gave it a chance. I think NASCAR let them do it in 57 first. 55 rear ends were the worst; 56 were better.,
     
  12. If they didn't hold up to 283s why don't know why G.M. would have used them behind 425 horse 409s and the Z-11

    I have two friends both in there 80s who raced Stock and Jr. Stock with 55-64 Chevys both said they never broke rears.

    One is still racing a Stock class 426 Max wedge and has one the U.S. Nationals twice.


    Oval trackers in the late 60s and early 70swould pull the 10 bolts out of Chevelles and use 57 and up rears because it is easier to change gears and because the axle shaft is a wear surface in a 10 bolt.

    My father was a line mechanic in a Chevrolet dealer he and others he worked with and remember replacing axles in Chevy II, and Chevelles when they were current models, because the bearing had wore into the axle.

    Most Oval tracks require C-clip eliminations on 10 bolts for safety.
     
  13. The 348-409 W engines came out later than 1957. NASCAR did permit them mainly due to the 7/16th wheel studs. Today they are mandated to use 5/8th studs due to the power and speed along with side loading stresses put on them.
     
  14. 59Apachegail
    Joined: Apr 30, 2011
    Posts: 1,378

    59Apachegail
    Member
    from New York

    Try https://tomsdifferentials.com
    Tom was a great guy who has passed but his daughters still operate the company. I know they sell OE style replacement truck axles you might get lucky and find a 5 lug axle from them
     
  15. junkman8888
    Joined: Jan 28, 2009
    Posts: 538

    junkman8888
    Member

    Apparently you want to keep the money out of this project, the cheap options are four-wheel drive S-10 and G-body at 58" wide, Camero / Nova at 61" wide, up to '66 Ford pickup at 60" wide. Best of luck with your project.
     
  16. 6-bangertim
    Joined: Oct 3, 2011
    Posts: 392

    6-bangertim
    Member
    from California

    To your first question and the naysayers there is a historical precedent 57 Chevy Black Widows Grand National cars used the Six lug truck rear and front hubs.


    Note rear cover and six lug wheels
    I've been told the 6-lug hubs and rear axles were used in '57 ambulance and airport limo applications - by a gent who spent TEN years in collecting research and parts to build a B-W clone. Sadly, he sold the car before I had a chance to look at it...
     
    Robert J. Palmer likes this.
  17. squirrel
    Joined: Sep 23, 2004
    Posts: 47,470

    squirrel
    Member

    If you're building a car to run NASCAR in 1957, then yeah, the truck rear might be a good choice. I kind of doubt that's the original posters intent, though.
     
    RICH B likes this.
  18. It is true the 348 and 409 came out in 58/62 , but the third members 55-64 are all the same. The axles and axle bearings 57-64 are all the same.

    NASCAR didn't just let Chevrolet use the truck rear it had to be available in the car, and it was as a taxi cab, ambulance, hearse option.

    There was a 57 Chevrolet ambulance in town @6-bangertim and it did have the truck six lug. I was too young to know what I was looking at the time but I remember my father telling me what it was.

    The barn it was in burned to the ground with the car in it.

    I am not saying these rears never broke but if they were as bad then as everyone claims now, there shouldn't be a 55-64 Chevrolet rear left.
     
    Last edited: Sep 28, 2020
  19. Nostrebor
    Joined: Jun 25, 2014
    Posts: 1,111

    Nostrebor
    ALLIANCE MEMBER

    Bumping in the rare hope that you get this thread back on track!:p

    I have never done one of these with the disk brakes, so no first hand experience here. The drum brake ones work fine FWIW. I'm hoping someone comes along with a good answer for you.
     
  20. squirrel
    Joined: Sep 23, 2004
    Posts: 47,470

    squirrel
    Member

    must have been hard to get parts for them, they 're not listed in the parts book.

    But my guess is that it was not something that was built by Chevy, rather, it was built by a coach builder, as most ambulances were.

    http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0465.htm
     
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  21. Gofannon
    Joined: Feb 8, 2007
    Posts: 602

    Gofannon
    Member

    57 Chevy Stock Car Competition Guide
    http://chevy.oldcarmanualproject.com/stuff/57csccg/57csccg07.html

    I have a 57 Chevy rear currently going into my GMC powered roadster. I have toyed with the idea of using a truck rear. 40-46 rears have a narrower housing, but have Huck brakes. Bendix brakes came about 52. Open drive carriers from 55-62 fit straight in to early torque tube housings. Early 12 bolt side gears drop straight in, allowing the use of modified 30 spline axles. This also implies a locker for a 12 bolt will also drop in. Toyota Landcruiser side gears and lockers also might fit. They use the same side and pinion bearings as 55-64 passenger car, but bearing caps are stronger. Also same pinion yoke which has a course spline.

    There are a lot of pics of old track roadsters with 6 lug rears.

    upload_2020-9-29_8-49-52.png
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 47,470

    squirrel
    Member

    I wonder what's different about that rear, that it requires a special gasket? The only reference I can find to it in the parts books is that it was removed in Nov 57.

    Interesting stuff
     
  23. Gofannon
    Joined: Feb 8, 2007
    Posts: 602

    Gofannon
    Member

    Gear sets are interesting as well. Looks like a mistake in the parts list. 3.55 - 4.11 would be passenger car gears, 4.56-6.33 truck gears. I only know of 4.11, 3.90, and 3.38 for open drive truck rears. 40's truck torque tube rears had 4.11 in 1/2 ton, 4.56 in 3/4 ton.
     
  24. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,282

    oldsman41
    Member

    To answer your question it is tight most guys put on coilovers and ladder bars here
     
  25. RUSS BUCKLIN
    Joined: Sep 18, 2017
    Posts: 143

    RUSS BUCKLIN
    Member
    from Seattle

    Hey guys,

    I'm really enjoying the discussion, I hope it keeps going. Getting a bunch of people who have been the done that talking about their experiences and knowledge is the best way to learn anything about anything.

    As for my project, I'm not necessarily trying to keep the money out of the project, it feels like I am spending a fortune already, but I don't want to spend money unnecessarily. So, for the rear, I wanted disks and posi. Disks not because they are better or worse but because they are easier to work on and they match the front removing the necessity of a proportioning valve, simpler overall. Posi because, well, I prefer to have two wheel driving the car from behind than one, no more complicated than that.

    So I sourced a 10 bolt 3.73 posi out of a 2003 Blazer 4x4. WMS to WMS width is 60" but backing plate width is narrower than the original torque tube rear. It looks like the leafs will just fit inside the Ebrake brackets on the calipers. I'll find out this weekend, the new perches arrive on Friday from Online performance. Axle swap perch kit for 49-52 Chevy car. I'll post pics of everything later today or tomorrow and any further comments, critiques and advice heartily encouraged. If I'm an idiot (yes) please point where so I can fix it.

    Thanks!
     
    Nostrebor and Gofannon like this.

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