Suburban 4x4 frame swap

[cal30_sniper]

I'm contemplating a 4x4 conversion on my C20 Suburban since I already have it torn apart for everything else I'm doing to it. I've already decided that if I decide to do this, I'd rather do a frame swap than attempt get all the 4x4 stuff hung properly on the front frame.

I've had two options pop up that are the same asking price, I was wondering if anyone here might have some input on pros and cons. The first is a late 70s K20 Suburban. The body is rusted all to bits, but the frame looks solid. It's got a Dana 44/14Bolt axle combo with a NP205 transfer case. The second option is a K30 SRW crew cab with a Dana 60 front axle and round pattern NP205 transfer case. I want to swap one of these frames underneath my 86 C20, with a round pattern NP205 or NP241 to mate up to my NV4500 swap.

I realize that the K30 frame would have to be shortened at the rear to get the proper wheelbase, and it is my understanding it's also about 5" too short between the axle and the rear bumper. I reckon this could be solved by cutting and shortening the frame ahead of the rear axle, and moving the rear axle forward a bit to lengthen the frame behind it. If I went this route, I'd get the round pattern NP205, Dana 60 front axle, beefier springs, and bigger 1-ton frame.

If I go the K20 route, it's a direct frame swap, but I get the weaker frame and smaller axles/springs. That, and I still have to source a round pattern transfer case.

Any input on the cost/reward benefit for going the K30 route? Would I be better off just getting the K20 and upgrading the axles/transfer case, or is the larger frame really worth it.

I tow a good bit with this thing, up to a 10,000lb bumper pull enclosed trailer. I'd like to keep my towing ability, while expanding my offroad capability a bit. I don't even plan to lift the truck, I just want something with drivewheels on both ends. Of course, I could always get the crew cab and keep it as a crew cab, but I really would prefer to have a Suburban body.

[SunSoaked]

K30

[cal30_sniper]

I didn't mention it in the first post, but a K30 based frame would also allow me to mount a larger trailer hitch on the frame as well. I'm currently limited to 10,000/1250 with a weight distributing hitch by the available hitches for the slanted Suburban rear frame. With a straight truck frame, I could step up to a larger Class V receiver hitch.

I've already got a 14BFF rear end, hydroboost conversion, a big block, and NV4500 trans. I just don't have the frame and springs that the 1-ton does.

[SunSoaked]

K30 X2 in that case.

[sweetk30]

frame shape / bends / dips are all different from suburban to pickup frame .

the only real frame advantage is the middle section is taller/deeper than 1/2 and 3/4 ton frames . after the frame humps up at the firewall forward and rear suspension there the same shapes .

so to put a suburban body on a c/k truck frame will require LOTS of MODIFICATIONS

[mongocanfly]

soon as I get done getting what I want to keep off it ,ill have a 3/4t 91 4x4 burb frame to get rid of...

[cal30_sniper]

Mongo, would that frame happen to come with front axle and transfer case? I'd be highly interested if that's the case.

[mongocanfly]

no axles...that's the main reason I bought it...I'm keeping front clip and front doors as well...maybe a few other parts....
transfer case and trans are still there...4l80 and np 241...

[Devilman]

Use the K20 suburban frame and tell me where the K30 frame is so I can go pick it up!! Lol I'm doing a 4wd conversion on my 78 crew cab and I'd rather swap frames than do all the retrofit stuff.

[sweetk30]

[cal30_sniper]

Originally Posted by Devilman

Use the K20 suburban frame and tell me where the K30 frame is so I can go pick it up!! Lol I'm doing a 4wd conversion on my 78 crew cab and I'd rather swap frames than do all the retrofit stuff.

I'll keep you posted. The wife gave me the okay to buy the entire K30 crew as a parts truck. I plan to strip the axles, springs, brakes, and steering stuff out of it to use with mongo's K20 Suburban frame. I won't have any use for the K30 frame and crew body when I'm through with it.

End result would give me a K20 Suburban with Dana 60 front, 14B full floater rear, NP205 or NP241, one ton springs and brakes, hydroboost, 8.1L, and NV4500. Should get me just about anywhere I want to go and do some towing while it's at it.

[SunSoaked]

You will have to relocate the spring pads and shock mounts on the 14ff axle. I just did this. Don't be tempted to reuse the mounts, buy new ones. Will save you a big headache. Currie makes the best tabs I have found. Heavy duty and very close to OEM specs. Summit racing has them.

[cal30_sniper]

Originally Posted by SunSoaked

You will have to relocate the spring pads and shock mounts on the 14ff axle. I just did this. Don't be tempted to reuse the mounts, buy new ones. Will save you a big headache. Currie makes the best tabs I have found. Heavy duty and very close to OEM specs. Summit racing has them.

That's because the 1-ton rear has narrower spring pad spacing, correct? My understanding is, and I could be completely wrong about this, is that the narrower 1-ton spring pad on the axle is due to different hangers on the frame (since the frames are the same width). If this is the case, I should be able to swap the K30 spring hangers over to the K20 frame and use the K30 axle and springs as is.

The other, would be to keep the C20 14BFF that's already underneath my truck, and swap the 1-ton springs over to the K20 frame with the C20 axle. It's kind of appealing to do it that way, since I already have a Richmond No-slip on my current 14bolt, but it's a 3.73:1 rear, so I'd have to regear the front axle to match. Probably just easier to swap the lunchbox over to the 4.10:1 K30 rear diff. I believe the K30 diff also sports larger 13x3.5" rear drums, as opposed to my current 13x2.5" rear drums. I'm not absolutely certain if that's the case though.

[SunSoaked]

I'm not sure about the difference in hangers but that makes sense. My axle came out of a cucv. If the frames are the same width, the only difference should be the bracket. That may be less work than swapping axle mounts, especially if you take the bed off. Regarding brakes, I know there are different sizes. My cucv are 13 x 3-1/2 I believe. They are heavy too-#50 per drum!

[KeithT712]

I'm doing similar frame swap currently, only half ton frame but still similar idea dana 60 and 14 bolt 4x4 frame with 2wd body. I think the suburban frame is a good route to go. My 14BFF bolted right up without having to move any perches or spring tabs and it was out of a pick up. Sounds like a good project! Curious to see how everything goes. I'm hoping to get my body on in a month or so. I think the floor pan may be an issue clearing the transfer case though but time will tell

[cal30_sniper]

Yeah, the floor pans are definitely an issue for the swap. I already have the high hump out of a mid 70s 4x4 installed in mine. That was part of the NV4500 swap I did a few years ago. Hopefully all I'll have to do in that regard is open back up the hole for the transfer case shifter.

[KeithT712]

Even better! Should be a pretty straight forward swap then, I've always wanted to do a nv4500 swap in something. Did I see right your doing an 8.1 swap also?

[cal30_sniper]

Yep, the 8.1 is sitting on the stand waiting to go in. I ported the heads, and dropped in a GM Performance 454HO cam with dual valve springs and comp roller rockers. Ported the intake also. Along with a free flowing intake and headers, with my special blend of tuning, it should be stout.

[Devilman]

Originally Posted by cal30_sniper

I'll keep you posted. The wife gave me the okay to buy the entire K30 crew as a parts truck. I plan to strip the axles, springs, brakes, and steering stuff out of it to use with mongo's K20 Suburban frame. I won't have any use for the K30 frame and crew body when I'm through with it.

End result would give me a K20 Suburban with Dana 60 front, 14B full floater rear, NP205 or NP241, one ton springs and brakes, hydroboost, 8.1L, and NV4500. Should get me just about anywhere I want to go and do some towing while it's at it.

I'll take it as long as the frame is straight and not rusted out. What year model K30 is it?