C30 info

[DINS 1]

is the frame on a c30 6in or 8in? Are the rear sections flat or do the have bends in them?

[SS Tim]

OK, Here you go but what are you trying to do? We started this once before http://67-72chevytrucks.com/vboard/s...d.php?t=527029. If you want a 1-ton suburban frame a Longhorn or a chassis cab is workable. Either way you need to address the wheelbase difference (move tubs?) and the rear body mounts. A C40 frame would be a lot more work.


CA210,310 is 7.20" 133"WB chassis cab,Longhorn 20/30 and C30 stepside
CA314 is 8.18" 157" WB chassis cab

The rails are bent similar to a pickup and the was a frame filler option to space the frame out flat forward of the rear axle.

Here is a picture of a C30 133 chassis cab.

[SS Tim]

Here is a drawing of about how a 133wb suburban would look. At one time I was thinking of a 1-ton drw (tucked in) for hauling horse trilers. It would be great with a polished airstream though. :-)

[DINS 1]

looking for a stronger frame than a 1/2 or 3/4 to to put my burb on with a durmax and an allison in. the 2004 frame is a 8" and i like the strenght that will provide for towing and other stuff.

[SS Tim]

Problem is you can't compare the two frames solely on the frame section height. If I remember the late frame you are referencing is one of Chevy's wider and heavier hydro formed box section weldments. Some of the advantages of the box frame are that its strong and light. If you use same the section height channel frame it might be close in bending (if it it heavy enough and has fairly wide flanges) but the torsion strength (resistance to twisting) is substantially less. Could be as low as 1/4th the value of a box frame. Building a Duramax out of an old suburban is a lot more that just swapping engines and in reality swapping a complete frame might be the best choice. But then your signature posts this intent already!?! Finally you have to choose between running the late independent 4wd front end or performing a straight axle conversion to the Duramax chassis. Also might want to read through Ryan's dieselwrencher Longhorn build to see some of the mods. he performed on his 1-ton frame. http://67-72chevytrucks.com/vboard/s...3&goto=newpost

[DINS 1]

The newer frame is hydro formed but is not a box section frame. I am most worried about the strenght for tow my 32 ft travel trailer and 24 enclosed trailer. i have a body setting on the fram but i am not happy the way the frame has to show to get the burb on the frame. the bottom of the rockers is just a couple inchs from the top of the frame so you see most of the center of the frame. the rear body mounts are setting on the frame so that you cannot lower the body any more with out large amounts of custom work. you can see this in the avatar photo

[SS Tim]

If it was hydro formed it is likely a box section even if it does not look very box like in cross section. Typical box sections will have load inserts welded to the inner and outer wall. Anyway did some research and I am now even less impressed with the GMT800 and 900s than I was before. Apparently the GMT800 series frame (like your 2004) is a weldment (like I thought), but is hybrid of hydro and stamped or rolled sections all welded together.
As far as seeing how these frames fit under your body the avatar is not helpful. Bigger would be a lot better but at this point only for documentation within the post.
Seeing as you don't want to modify much, understandably, then your choices are pretty much limited. First is a C30 133" 1-ton frame and alter the wheel wells to match the new wheelbase. It also shortens the overhang moment of the trailer hitch. Second would be to alter the C30 133 frame to a 127" wheelbase and fit it up to your body. Basically I understand it pretty easy to make a suburban frame from a pickup.
Third choice and the most work but the heaviest stock type frame would be to use C30 157" frame and bring it down (mid section cut/splice) to 133 or 127" as you desire. With any of the above options duals could be used but it would be really narrow between the housings on a tuck under. Lots of examples of that look here. http://67-72chevytrucks.com/vboard/s...d.php?t=536253
From your PM you seem to be in a hurry for the info and I will be around if you wish clearification on anything.

[SS Tim]

I hesitate to add these pictures as the truck is virtually impossible to find. It is a C30 with the 11K rear axle. Pretty much a medium duty truck in disguise. However the modulus numbers are the same as the lighter 157s so they might be very similar.

[OldCreek]

There are a couple of C30 campers being parted out in the for sale section with a 157" wheelbase frame (in Cali)....

I'm using the same frame in my K3500 conversion. However, here are my observations:

The rear frame section, 8", kicks up higher than on a regular truck frame. Therefor, you will have to run an approx 3.5-4" body lift to match up with it. That will, in effect, also expose the frame. To combat that, I am mounting up side steps/bars to hide that.

Also, I could be wrong, but the frame in front of the firewall seems to be of the SAME dimensions/modulus as all other trucks. I suspect if you're looking for a beefier frame to handle the torque you may still need to box that front end.

Best of luck!