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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Topic started by: mar-tay1 on October 15, 2014, 11:49:41 AM

Title: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: mar-tay1 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!
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: zieg85 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Engineer 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Blazin 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Dan75k20 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
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: pholliday1 on October 16, 2014, 02:36:01 PM
X2 Engineer
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Papawoodi 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: zieg85 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Engineer 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Blazin 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Irish_Alley 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: pholliday1 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.
Title: Re: 1/2 ton frame vs 3/4 ton frame - 2wd or 4wd
Post by: Irish_Alley 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.