frame swap for a 4x4

[prg machine]

I am told that a GMC 2wd frame can be converted to a 4x4 by using the front spring hangers from a K truck and a front crossmember????

Does anyone know for sure how this is done?

[Longhorn Man]

I'll move this to the 4X4 section. They can probably tell you every little tidbit you need to know.
With that being said... I *THINK* it can be done, and probably takes what you listed, and then the 4X4 steering gear box and a few other odds and ends.

[prg machine]

yea, I posted around in frame and suspension and the 4x4 forum and here also hoping for attention.

does the steering box bolt to the 2wd frame without trouble?? I never thought there would be a difference. I have everything on my K truck to swap over. I straightened the frame as best I could but it still favors pulling slightly right, just enough that I know it and wish it didn't. For now the truck is used minimaly and only short distances. Someday I would like to swap.........................or find a shortbed frame!!!!!!!!

[sweet70beast]

I know a guy that did just that. He told me that other than a few minor things it is basicly a bolt in, all the holes are already there. I didn't see the before but I did see the after and you'd never know it was a conversion. I've got my eye on a 71 Chev with rear leaf springs and if I can get my hands on it I will do a conversion to it.

[GMCMAX]

All the holes aren't there, but it's not hard to drill the ones that aren't. If the 2wd frame has rear leaf, you're a step ahead. One of the PITA things on my 68 was flattening out the dimples in the front where the e-brake cables go through. The other was that the 2wd rear end spring hangers are shorter and it took a 4" block to make it sit level with the stock 4X4 front springs.
The 4X4 power steering box bolted right up on mine.

[prg machine]

and is there any difference in the 3/4 ton to the 1/2 ton frames in consi9dering this swap????

[Dieselwrencher]

Like mentioned all the holes are not there. Mainly for the shackle mount for the front spring. I am in the process of doing this to my 72 longhorn. When i get it far enough I will post up pics and info. I am planning on cutting the part of the frame where the e brake knotches are and installing a flat piece of steel there so it looks factory. I may even replace the rear spring hanger because I am using 6" lift springs in the front and if I don't replace that hanger, I will need a 10" block. LOL I think the biggest difference in the frames, is the 1/2 frame rail heighth is shorter than the 3/4. But I am not 100% on that.

[maximum destruction]

Originally Posted by Dieselwrencher

Like mentioned all the holes are not there. Mainly for the shackle mount for the front spring. I am in the process of doing this to my 72 longhorn. When i get it far enough I will post up pics and info. I am planning on cutting the part of the frame where the e brake knotches are and installing a flat piece of steel there so it looks factory. I may even replace the rear spring hanger because I am using 6" lift springs in the front and if I don't replace that hanger, I will need a 10" block. LOL I think the biggest difference in the frames, is the 1/2 frame rail heighth is shorter than the 3/4. But I am not 100% on that.

actually, the 1/2 ton & 3/4 ton frame heights are the same, as well as some 1 tons. the rails are indeed taller on 1 tons that were designated for dumps, box trucks, ambulances & military cucv's.

[prg machine]

so 1/2 ton and 3/4 ton frames were the same dimensions and material strength?

[Jtrux]

Interesting thread, I have a 69 chevy parts truck with rear springs, might have a new project after all.

[maximum destruction]

Originally Posted by prg machine

so 1/2 ton and 3/4 ton frames were the same dimensions and material strength?

as far as i know, the 1/2 & 3/4 trucks, blazers, & suburbans use the same thickness in the steel. 1 tons are thicker & as i said before, depending on their intended use, some had a physically taller rail. however, i don't remember the time span when gm changed the steel in their frames. i believe late 70's or early 80's.? maybe someone else here can pinpoint that for u.

[prg machine]

okay, I have located a 1/2 ton longbed frame from a chevy with the rear leafs. The guy thinks that the 1/2 ton might have a slightly narrower, like 1 inch per side or so, set up in the rear spring hangers or the rails themselves, than the 3/4 tons?????


I guess the problem is putting the 3/4 axles under the 1/2 ton frames in the rear.

anyone know anything about this fact???

[Dieselwrencher]

And another thing, you will need the bumper brackets from the 4wd truck in the front because 2wd and 4wd are different.

[72-c20]

Originally Posted by Dieselwrencher

And another thing, you will need the bumper brackets from the 4wd truck in the front because 2wd and 4wd are different.

I thought the bracket difference was because of the frame, and the bumpers were all the same?

[Dieselwrencher]

Originally Posted by 72-c20

I thought the bracket difference was because of the frame, and the bumpers were all the same?

The bumpers are the same. But, the 2wd brackets go behind the rad support on the frame and on the 4wd they bolt right into the pocket of the rad support mount at the frame.

[Dieselwrencher]

I am going to measure this blazer 4x4 frame I have and the longhorn frame I have to compare. I never have done it, the 3/4 tons just look bigger in the frame area I guess?

[padresag]

measuring your blazer frame and your longhorn frame is going to tell you what?
I do have a suburban 2 x 4 frame and my panel 4 x4 frame and the 4 x 4 is 1" deeper. mine are same year , same w/b
ron

[prg machine]

so what about the width at the rear spring hanger area????

[Dieselwrencher]

Originally Posted by padresag

measuring your blazer frame and your longhorn frame is going to tell you what?I do have a suburban 2 x 4 frame and my panel 4 x4 frame and the 4 x 4 is 1" deeper. mine are same year , same w/b
ron

It will tell me that a 4x4 1/2 ton frame is different than a 2x4 3/4 ton frame. This is what I found in my measurements.
These measurements were taken from top to bottom of frame flanges. And both frames were 1/4" thick. The Bold is for the longhorn to try to see the difference in the post.

1972 Blazer 4x4 1/2 ton 1972 Chevy Longhorn 3/4 ton 2x4
6 1/8" tall behind front cab mount 7 5/8" tall behind front cab mount 1 1/2" difference
4 1/2" Tall above rear axle 5" Tall above rear axle 1" difference

Rear Spring Hangers On Frame
Front Front
10" 5 1/2" 4 1/2" difference
Rear Rear
7 1/4" 7 1/4" Same

So what this shows me is that the frames are different from 1/2 ton to 3/4 ton. Now this could be different with the 2wd coil spring rear suspension trucks. But not with the leaf spring 3/4 ton trucks. Basically the 2wd 3/4 ton frame I have is the same as a 4wd frame almost. Since some holes are different up front I realize they are different. But that shows a comparrison on frame heighth.

And for the rear leaf spring hangers. I had it backwards. Everyone told me the rear hanger was longer on the 4wd's than the 2wd's. Well in reality it is the front hanger that is almost 4 1/2" longer than the 2wd one. That is a big difference. And the rear ones are the same.

[prg machine]

http://www.chuckschevytruckpages.com/framespecs.html

the "S" dimensions don't make any scence to me for longbed/shortbed trucks................??????????

[padresag]

Originally Posted by Dieselwrencher

It will tell me that a 4x4 1/2 ton frame is different than a 2x4 3/4 ton frame. This is what I found in my measurements.
These measurements were taken from top to bottom of frame flanges. And both frames were 1/4" thick. The Bold is for the longhorn to try to see the difference in the post.

1972 Blazer 4x4 1/2 ton 1972 Chevy Longhorn 3/4 ton 2x4
6 1/8" tall behind front cab mount 7 5/8" tall behind front cab mount 1 1/2" difference
4 1/2" Tall above rear axle 5" Tall above rear axle 1" difference

Rear Spring Hangers On Frame
Front Front
10" 5 1/2" 4 1/2" difference
Rear Rear
7 1/4" 7 1/4" Same

So what this shows me is that the frames are different from 1/2 ton to 3/4 ton. Now this could be different with the 2wd coil spring rear suspension trucks. But not with the leaf spring 3/4 ton trucks. Basically the 2wd 3/4 ton frame I have is the same as a 4wd frame almost. Since some holes are different up front I realize they are different. But that shows a comparrison on frame heighth.

And for the rear leaf spring hangers. I had it backwards. Everyone told me the rear hanger was longer on the 4wd's than the 2wd's. Well in reality it is the front hanger that is almost 4 1/2" longer than the 2wd one. That is a big difference. And the rear ones are the same.

what I can't understand is trying to figure out a comparison between a blazer chassis to a 3/4 ton chassis,.I can see comparing a 127" w/b 1/2t 2 x 4 chassis to a 127" w/b 3/4t 4 x 4 to see what the differences are other than crossmembers and suspension orientation.
ron

[Jtrux]

Originally Posted by padresag

what I can't understand is trying to figure out a comparison between a blazer chassis to a 3/4 ton chassis,.I can see comparing a 127" w/b 1/2t 2 x 4 chassis to a 127" w/b 3/4t 4 x 4 to see what the differences are other than crossmembers and suspension orientation.
ron

It's because it's what he has, the comparison is between a 1/2 ton and 3/4 ton more specifically 1/2 ton 4x4 to 3/4 ton 2x4.

[padresag]

don't know. best thing to do is find the chassis in question which is opposite what you have and measure it for yourself; then you know exactly what the differences for. you will get a variety of answers on these boards. always confirm what you need to know and that will alleviate any foreseeable problems
ron

[manimal]

look for grendel he has done this and posted the whole build up. AWESOME work he's done. Good Luck
-Lance

[GMCMAX]

Dang, sorry, it's for 73-87.......... thought I had another link for ours, but can't find it.
Check this link from Chuck's Chevy pages, it gives frame dimensions
http://www.chuckschevytruckpages.com/framespecs.html