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frame differences - 1/2 ton to 3/4 ton?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jersey, Dec 17, 2002.

  1. Jersey

    Jersey 1/2 ton status

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    Are there any frame differences between the 1/2 ton and 3/4 ton Chevy/GMC pickups? Just wondering if the frame is any stronger, more heavy duty on the 3/4 tons. Any info is appreciated in advance. Thanks.

    - Jersey
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    My GM service manual mentions that the frames can indeed be made of different materials (and that the frames are stamped to denote that) but there is no indication given for thickness, or which applications received what frame.

    For sure the 1 tons are different, I really need to use the dial calipers on my dads 3/4 ton and my K5.
     
  3. woody9

    woody9 1/2 ton status

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    dug this outta my spec book once.. and Yes! At least on Suburbans! /forums/images/graemlins/burb.gif There's a tad more beef in the 3/4 than in the 1/2. A radius here, a dimension there... not a lot, but one that i recall was the thickness if i remember right. My list is on 91's.. but will dig it out if you need more.
     
  4. thatK30guy

    thatK30guy 1 ton status Premium Member

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    When comparing a regular cab LWB 1/2 and 3/4 ton frame to each other, no, there are no differences.

    Well, at least there are no differences on either from '73 to '79. Both are identical and are the exact same thing for the other. These years use the 52" rear springs.

    The '80 to '87 frames are also identical, except for the 3/4 tons very rearward part of the spring hanger brackets, the shackle end, is located 4" further back than the 1/2 tons. This 4" rearward location is the reason for the 56" rear springs.
    But both frames are identical since both 1/2 and 3/4 ton have the holes stamped/drilled from the factory for either location of the shackle hanger. Just a matter of installing the hanger from the factory to whatever line of axles were being built. Example: 1/2's had the hanger mounted at the forward holes and 3/4 tons had the hangers mounted to the rearward holes.

    The LWB trucks share the exact same frames. Only the SWB, Sub, Blazer, K30, crew cab all have their own frame. /forums/images/graemlins/wink.gif
     
  5. wrathORC

    wrathORC 1/2 ton status

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    My 77C20 had 56" springs. The springs, hangers, and axle are still hooked together. The rest of it is probably melted by now.

    The frame had different holes drilled in it than my 84K10 does. It also had some different bracing under the box. The holes to mount the gas tanks were also different by 1 hole on the front bracket. Like my 84, the 77 had holes on the sides for both the 52" and 56" springs. The 77 didn't have the holes for the underside braces for the taller spring hangers though.
     
  6. thatK30guy

    thatK30guy 1 ton status Premium Member

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    '77 and '84 are two whole different frames. There is nothing matching on those two years as far as all the brackets and hangers go. Even the cab mount brackets are all different between the two.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Check up on the front frame horns. Not sure if they did this earlier on, but the frames supposedly will have shaped cutouts somewhere up there, that indicate frame material.

    Just wondering if that was a difference GM made based on application (1/2 vs 3/4) or if it was simply a difference based on where the frame was made.

    Probably less to do with strength than knowing what a service person might end up welding on, but there are different frame materials for sure, at least some years.
     
  8. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Yep, that's right, the older frames are more "rounder" up there than the newer ones, which have more of a "triangler" shape.

    The year split is between '80 and '81.
     
  9. Jersey

    Jersey 1/2 ton status

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    THANKS MUCH

    Thanks for all the info! Appreciate it much. Reason i'm asking, my buddy is looking to get a 78-80somthing chevy or GMC pickup. Here in Jersey, it's tough to find one that's not beat to heck and rusted almost beyond repair for around 3k or less. He want 8ft bed and single cab, obviously because they didn't make the extended that early. He's been looking at 1/2 tons because they're in a little better condition than the 3/4 tons and i mentioned to him that i know about the axle/spring differences but wasn't sure of the frame differences, if any. I figured he should start with a strong base from the start and, just about everything can be changed, except the frame. He also mentioned getting a 2WD, because again, you can find one of those ever cheaper, in better condition for that price, and down the road, converting it into 4wd. Told him it might be more work than wanted, even though he does work for detroit/allison, and to keep an eye out for a 4wd, 3/4 or 1Ton with a decent body. I hate rust but can drop a motor in, swap axles and whatever else mechanically easier than battling rust. Any other opinions on what way to direct him in, or, thatk30guy...if you'd like to sell that beautiful K30 you have for cheap, let me know /forums/images/graemlins/deal.gif Thanks again guys.

    - Jersey
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    No, what the manual was saying is that there will be actual cutouts in the frame shaped like a diamond or something else, that corresponds to the metal composition.

    I'll have to look that up again if I remember. You can bet it wasn't something I was looking for at the time, and it was probably buried in the manual.
     
  11. thatK30guy

    thatK30guy 1 ton status Premium Member

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    "Diamond"..."triangle"...kind of the same thing.

    Anyways, I just installed a bumper on an '82 and you can clearly see the differences between the '82 and say, a '74 frame horn. Neither bumper will fit the other year. Nor will the bumper brackets either.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Still think we're communicating different things /forums/images/graemlins/smile.gif

    I'm saying somewhere on the frame (I seem to recall it was on the frame horns, but ignore the location for now) there CAN be a cutout that is either in this shape
    ../\
    ./..\
    /....\
    ------

    or
    ../\
    ./..\
    /....\
    \..../
    .\../
    ..\/

    Now I'm talking about something that was cut/stamped out of the frame during construction, during the SAME model year.

    Now, again, I just saw it in passing, so I can't recall the actual shapes, but they would obviously be something like the above. So for say a 1982 truck, one frame might have a diamond cut out on the frame, and in the same location on another 1982 truck, it might be a triangle, or circle, or square.
     
  13. R72K5

    R72K5 Banned

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    its the 1 ton frames that are taller rails than other series frames
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    For the record, was looking in my 85/86 parts manual (didn't find the info) and there are *14* different 4wd frames alone for those years.

    (K10/20/30) four 1/2 ton frames, three 3/4 ton frames, and seven one ton frames.
     
  15. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I need to take some pics of the frame differences. /forums/images/graemlins/tongue.gif /forums/images/graemlins/laugh.gif

    I have a bare '85 SWB frame laying in my yard. I can easily get pics of the frame horns here.

    I know where an '80 K20 frame is laying, bare, and will get pics of those frame horns, too.
     
  16. thatK30guy

    thatK30guy 1 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    its the 1 ton frames that are taller rails than other series frames


    [/ QUOTE ]
    Yes, they are "taller" on the channel part under the cab, but they are not "taller" so to make the K30 sit taller than the smaller trucks.
    The added height to the frame actually goes down, rather than up, in the height. The bottom of the rail sits lower than a K20 or K10 on a K30.
     
  17. m j

    m j 1/2 ton status

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    and the added breadth is only between the axle centrelines
    the front frame horns and rear frame horns are the same as the 1/2 3/4
     

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