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1/2 ton frame vs 3/4 ton?

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I got a 80 1/2 ton frame under my truck.
I should be getting a 81 3/4 ton truck for parts in two weeks.

Is the 3/4 Frame any better than what I got...stronger, thicker. Or are they the same?

I know the rear springs are longer but what else is different.
 
Ive always heard reports that the dimensions themself were the same but the 3/4 was thicker than the 1/2. Obviously the 1ton is both thicker and narrower in the back.
 
Spec sheets on the 60's trucks showed that they were thicker in that generation. The best I have been able to tell from the 70's and 80's trucks is they were 100% identical on the long bed trucks. Only the short bed and K5 frames have had thinner material that I have noticed. However if you have a set of calipers handy, just measure the thickness of the metal in two or three locations while you have them side by side and you will know for sure.
 
there are measured stats around here for that.. I remember a thread in here ages ago about it... maybe someone can dig it up, it was awhile ago tho..

iirc, the 1/2 and 3/4 where virtually identical on thickness... just a couple thousands dif.. but the 1 ton was a fair bit thicker comparatively as far as numbers went...
 
Right,I knew the 1 tons are thicker.

So probably not worth the time to do another frame swap from 1/2 to 3/4 more than likely then.
 
kennyw said:
Spec sheets on the 60's trucks showed that they were thicker in that generation. The best I have been able to tell from the 70's and 80's trucks is they were 100% identical on the long bed trucks. Only the short bed and K5 frames have had thinner material that I have noticed. However if you have a set of calipers handy, just measure the thickness of the metal in two or three locations while you have them side by side and you will know for sure.
Click to expand...

Actually that make sense, the 78 shortbox I used to have had cracks all over the frame. But it lived a hard life!
 
And a couple thousandths difference in thickness can be accounted for by acceptable tolerance range. Hot rolled plate in the 1/4" thickness can have a +.030/-.010" tolerance range. These frames likely had a little tighter thickness tolerances, but I don't know where to dig up the exact numbers as it is probably hiding in a basement at GM.
 
exactly.. we're not talking space shuttle parts here..
 
I can only say, having recently cut up part of my '68 C20 long bed, that it is visually thicker than my 67-72 C10 short bed.

Sorry, no other knowledge at this time :D


EDIT: Just measured so I would stop calling myself lazy.

.188 vs .250
Some fluctuations. The C20 frame was .250-.288. Never C10 thin
 
and your also talking first gen.. it may have been more of a dif in those days, as opposed to the 80's "let's build em as cheap as we can" days.....
 
ryoken said:
and your also talking first gen.. it may have been more of a dif in those days, as opposed to the 80's "let's build em as cheap as we can" days.....
Click to expand...

That is not first gen for a truck... but the sales brochures listed frame specs in the 1960-66 era with noticeable differences in the frame thicknesses. I think the frames in the 1967-72 era were very much the same (but I haven't owned them or have anyway to prove it).

It is more likely that they designed the 1973-87 frame for the payload of the 8600 GVW 3/4 ton and made all of the long bed frames the same because it is cheaper to produce higher quantities of one frame than lower quantities of two frames.
 
All I know is my '56 3200 series pickup had frame rails at least 5/16" thick...

All the trucks I've owned newer than that one had no more than 3/16" thick rails,and most were 1/8" or less after I owned them a few more years thanks to salt ,they flaked layers off like delaminating plywood...the '56 frame still had paint and looked nice though,in 1984 when I sold it!--"they dont make them like they used too" applies here I guess..better virgin quality steel then too probably..not recycled crap....the frame on my 77 GMC was so thin near the fuel tank I could see pinholes ,that was the final straw,I would have put another tranny in it and kept driving it,if not for that...my 82 K2500 frame is getting long in the tooth in some spots now too,sadly..but it is 32 years old too,and its seen a lot of salt exposure..
 
76zimmer said:
about as detailed as it gets for this subject:

http://coloradok5.com/forums/showthread.php?t=235499&highlight=frame+thickness
Click to expand...

Thanks Dave very interesting! :thumb:

diesel4me said:
All I know is my '56 3200 series pickup had frame rails at least 5/16" thick...

All the trucks I've owned newer than that one had no more than 3/16" thick rails,and most were 1/8" or less after I owned them a few more years thanks to salt ,they flaked layers off like delaminating plywood...the '56 frame still had paint and looked nice though,in 1984 when I sold it!--"they dont make them like they used too" applies here I guess..better virgin quality steel then too probably..not recycled crap....the frame on my 77 GMC was so thin near the fuel tank I could see pinholes ,that was the final straw,I would have put another tranny in it and kept driving it,if not for that...my 82 K2500 frame is getting long in the tooth in some spots now too,sadly..but it is 32 years old too,and its seen a lot of salt exposure..
Click to expand...

Yeah,i had a 66 GMC NAPCO 4x4 That frame was stout.
 
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