4x4 frames...k10 vs k20

[manimal]

Ok, before people starting posting.."SEARCH", I have, nothing definitive has been posted, no actual information.
So my question is, for those who have a STANDARD CAB LONGBED K20 4wd, can anyone measure the thickness of the frame rails for me. I have a K10 LWB frame, I have gone on GM Heritage and read the info there, but then I have seen postings of frame thicknesses before and none of that info matches. I am wanting to build a K20 out of it, but I want REAL LIFE measurements to match my frame to.
Thank you.

[andyh1956]

All I have is an 84 K30 Camper Special, the rest are K10s.
I know the frame is taller on that 30 but I will measure thickness for you if you think it will help you.

[D13]

1977 Heritage Center shows K10 LWB and K20 LWB both have 3.92 frame modulus, so the frames are the same.

As far as actual measurements, you would need a clean unrusted unpainted frame and then measure each individual section shape.

i can tell you here in Michigan 100% thinning is common. Like, missing from salt corrosion LOL.

[SunSoaked]

I've been wondering for some time what the "Heavy Duty Frame" on my 85 K20 means. That's what it says on the SPID. Was there a "regular or light" duty frame?

[dmack91]

I have an 83 K20 and just forward of the rear cross brace, the frame measures 4 3/4" tall, 3 1/4" wide, and 3/16" thick. Best I can do with a tape measure in the dark. If you need something else or more precise measurements, let me know.

[manimal]

Awesome, THANK YOU to all of you.

[D13]

Originally Posted by SunSoaked

I've been wondering for some time what the "Heavy Duty Frame" on my 85 K20 means. That's what it says on the SPID. Was there a "regular or light" duty frame?

Yes, there is a 'heavy' duty 3/4 ton frame available. Weight was taken out of the frames in the 1981 redesign, but there was still an need for a stronger frame for certain applications. Usually goes along with HD suspension, most common on the military pickups and firefighting units that we always heavily loaded.

[sweetk30]

Originally Posted by D13

Yes, there is a 'heavy' duty 3/4 ton frame available. Weight was taken out of the frames in the 1981 redesign, but there was still an need for a stronger frame for certain applications. Usually goes along with HD suspension, most common on the military pickups and firefighting units that we always heavily loaded.

military pickups were k30 1tons . totaly different frame size . and most fire truck ambulances were build on these frames also . i have seen some k20 fire trucks but not a lot .

2 easy ways to spot a k30 only frame is the middle section of the frame like under the cab is 8.25" tall almost 2" more than 1/2 and 3/4 ton frames . and in the rear 1ton frames had inboard shocks on a set of 4 bolt riveted in frame ear studs . this was cause the outboard shock design of 1/2 and 3/4 ton would not clear the leaf springs being sucked in 1" each side to make room for the narrow c&c axle option if it was to be a drw c&c truck .

[SunSoaked]

I found my rpo code (C6P) actually states HD Chassis so it may have nothing to do with the frame, rather the springs? Swapping in the 14ff & Dana 60 probably only lowered my payload capacity. Lol. Of course I probably gained it back when I swapped to the Vintage Air system and lost 300 lbs of useless wires, vacuum hoses, cables and connectors.

[Caminuvik]

Originally Posted by sweetk30

military pickups were k30 1tons . totaly different frame size . and most fire truck ambulances were build on these frames also . i have seen some k20 fire trucks but not a lot .

2 easy ways to spot a k30 only frame is the middle section of the frame like under the cab is 8.25" tall almost 2" more than 1/2 and 3/4 ton frames . and in the rear 1ton frames had inboard shocks on a set of 4 bolt riveted in frame ear studs . this was cause the outboard shock design of 1/2 and 3/4 ton would not clear the leaf springs being sucked in 1" each side to make room for the narrow c&c axle option if it was to be a drw c&c truck .

Would this be applicable to earlier years? I have the shocks inrail, yet the rails under the cab look to be more closer to 6" tall (I will check more carefully.) It does have a full floater rear end. Not sure at all of the original configuration of the truck. Thanks

[MJN]

Originally Posted by Caminuvik

Would this be applicable to earlier years? I have the shocks inrail, yet the rails under the cab look to be more closer to 6" tall (I will check more carefully.) It does have a full floater rear end. Not sure at all of the original configuration of the truck. Thanks

I could be mistaken but the pre-CUCV (1976ish era) Canadian military pickups were K20's with Dana 44 front axles and would explain the 6" frame rails vs the later K30 trucks (not in production until 1978) and CUCV's that used the 1-ton frame with 8" rails. Both would have the full float rear axle. Some more research would have to be done to determine if the Canadian trucks were equipped with heavier rear springs and used the inboard shocks the 1-ton's used.

[manimal]

If someone that has a K20 would actually measure thickness with calipers or micrometer, I can do the same for the K10, and someone with a K20 CAMPER SPECIAL could do the same thing, we can FINALLY put this to rest. I will take measurement in 3 locations, right in front of engine crossmember, under cab and around area of tow hitch. I will clean these spots well and post my findings.

[dmack91]

I mic'd my K20 in three spots and they ranged from .225 to .255.