Author Topic: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd  (Read 18987 times)

Offline mar-tay1

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1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« on: October 15, 2014, 11:49:41 AM »
 I am looking to put together another 4x4. This time starting from the ground up using as many of the spare parts I have from several 73/74 c10-c20 trucks I have around here, and trying to figure the best combo to go with.  It stands to reason that a 3/4ton 4x4 would be my best bet. Putting a set of leafs up front on a 1973 c10 would work best for me but thought the frame is weaker, and didn't know if that was just dumb or would it be even better due to flexing more? I have an 8 lug 14 bolt and a front dana44 that I'm setting up for crossover steering, several transmissions to choose from and just figure what transfer case I want to run. I'm not going to be rock crawling, just want it to be capable and resilient, and I'm over 40 so more than likely I wont be beating it too hard. You never know though? Any recommendations, tips, or advice is greatly appreciated! Thanks!

Offline zieg85

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #1 on: October 15, 2014, 12:33:45 PM »
1/2 ton and 3/4 ton frames are supposed to be identical except for the rear shocks mounting inside the frame on a 3/4 ton and the outside on 1/2 tons.  Frame height and thickness is the same.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Engineer

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #2 on: October 15, 2014, 04:52:42 PM »
Zieg-

All of the 3/4 4x4 frames I have seen have the shocks mounted outside the rails like the 1/2 tons. All of the 1-tons are mounted inside the rails. As far as that goes, I have never found any difference between a 1/2, and 3/4 frame. Now the 30 series is a whole different story. Lots of differences in the 30 trucks.

OP-

IMHO, if I were looking to build a 4x4 from a 2wd I'd look for a 4x4 frame to start with. I know many on here have converted 2wds into 4x4s, but I guess it all comes down to how much work you want to invest in your project. For me swapping a body onto a frame would be easier than drilling rivets and holes to put the leaf brackets in the front of a 2wd frame. Others may find it is easier to hang the leaf brackets than swapping the body over.

Again, JMHO.
2002 Chevy 2500HD 4x4 8.1/ZF6sp RC/LB
2001 Chevy 2500HD 4x4 6.0/4L85E EC/SB
1997 Chevy Blazer 4x4
1994 Chevy K-2500 4x4 C6P 5.7/4L80E
1979 Chevy K-30 4x4 4sp 4.10
1977 Chevy K-30 4x4 4sp 4.10 454

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Offline Blazin

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #3 on: October 15, 2014, 07:19:14 PM »
Keep in mind if you use the two wheel drive frame you will have to swap the front rear spring shackles too.
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Offline Dan75k20

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #4 on: October 15, 2014, 10:27:20 PM »
I thought all k 10s and k20s had the shocks mounted inside the rails ? Iirc ? And the frame rail width was the same except for k30s

Offline pholliday1

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #5 on: October 16, 2014, 02:36:01 PM »
X2 Engineer
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Offline Papawoodi

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #6 on: October 17, 2014, 08:21:32 AM »
Good to know, I thought there was a difference between a C10 1/2 ton frame vs C20 3/4 frame (thickness, width, etc). Was debating on getting a C20 frame for my build but now I see C10 frame is the same.
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Offline zieg85

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #7 on: October 17, 2014, 10:18:43 AM »
1/2 ton and 3/4 ton frames are supposed to be identical except for the rear shocks mounting inside the frame on a 3/4 ton and the outside on 1/2 tons.  Frame height and thickness is the same.

I stand corrected... I've been working on 1 tons mainly.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Engineer

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #8 on: October 17, 2014, 07:20:56 PM »
Frame rail width is the same on all 73~87(91) Chevy/GMC trucks.

Starting just in front of the front cab mount to the rear of the frame, all are 34" wide. Just like an 18-wheeler.

The C30/K30 rear springs are narrower on the axle (closer together) than the C/K 10/20s.
2002 Chevy 2500HD 4x4 8.1/ZF6sp RC/LB
2001 Chevy 2500HD 4x4 6.0/4L85E EC/SB
1997 Chevy Blazer 4x4
1994 Chevy K-2500 4x4 C6P 5.7/4L80E
1979 Chevy K-30 4x4 4sp 4.10
1977 Chevy K-30 4x4 4sp 4.10 454

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Offline Blazin

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #9 on: October 17, 2014, 09:15:50 PM »
Springs are the same width apart on C, & K30s. The rear axle on a cab & chassis is narrower, the baking plate is closer to the spring pack than 1/2, 3/4, 1 ton pickups & Duallies.
The frame height is taller on the 1 tons starting right behind the rear of the front springs. Width is the same on all Chevy trucks 73/87.
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline Irish_Alley

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #10 on: October 20, 2014, 02:16:57 PM »
3/4 tons are a little thicker vs 1/2 (.040) cant remember exact number but its only like 3/64". besides that i think they named the other differences.  i would get the parts off a 4x4 and put them on your 4x2.
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Offline pholliday1

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #11 on: October 20, 2014, 10:27:58 PM »
Get the micrometer out! Inquiring minds want to know lol. Take your measurement on bare metal,heck you could have 3/16 in frame paint. Irish you have me curious, I'm gonna measure mine now.
« Last Edit: October 21, 2014, 02:30:02 PM by pholliday1 »
VETERAN AND LIFETIME NRA MEMBER. WHAT DO YOU STAND FOR?
1991 V3500 CREWCAB SRW 454TBI GMC
1991 v3500 crewcab SRW 454tbi 480le 6" lift
1990 V3500 crewcab Dana 60 FF 14b 5:38 ratio 40 inch 11" lift
1989 v3500 crewcab 454TBI 5" lift

Offline Irish_Alley

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Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
« Reply #12 on: October 21, 2014, 03:19:14 PM »
Then you also have to deal with rust Or lack of. But best info is from here

http://forum.73-87chevytrucks.com/smforum/index.php?topic=28217.0

All seven of these C10/ Big 10 GVWR packages used the same basic frame with a side rail width, depth, and thickness of 2.30”, 5.92”, and .156” respectively.


similar breakdown can be made for the C20 regular cab pickup, which was available for ’75 with GVWR’s of 6,400, 7,100, 7,500, and 8,200 lbs. All four of these GVWR packages shared a frame with a side rail width, depth, and thickness of 2.30”, 5.92”, and .194” respectively. While the side rail width and depth were the same as the C10/Big 10 frame, the thickness was greater, and in fact was the same as the thickness of the frame used in the one ton C30. Not surprisingly, the frame section modulus, at 3.92, was also more robust.
If you cant tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes