3/4 ton vs. 1/2 ton frames

[sclark81]

Hello all...I'm new here and could probably search for this for hours, but it's quicker to ask.  Is there a difference between a K10 frame and a K20 frame?  I have a K10 frame at my disposal and could put all 3/4 ton brakes and suspension under it no problem, but I didn't know if the frames were heavier or not.  I'm wanting to build a "spare" if you will, to my 2002 chevy 2500 hd crew cab 4x4 with 8.1 and Allison tranny.  We've got a 32' 5th wheel camper we tow sometimes and we also have a 27' boat that weighs in around 8k total with trailer. 

What would you guys recommend?  I was going to build a K20 with a 454 and 4 speen sm465.  Small lift of maybe 4" or so and 33's.  Nothing huge.  It still wouldn't pull as hard as the 2002, but it would get the job done in the event of a break down on the 02.  I have a 454 in pieces that needs a rebuild, a rebuit 427 tall boy, 400 turbo w/205 transfer case, and a 4speed sm465 with 205 transfer case all just sitting in the garage.  I just can't make up my mind what to run for power that would even come close to the 8.1 / Allison combo.  Any thoughts are greatly appreciated!

[choptop]

I believe the 3/4 ton frame is heavier, so I am not sure about the benefits of swapping the parts over to the half ton frame other than having a bad boy 1/2 4x4. I may be wrong on the frame. As far as building a truck to pull as good as your 02, Oh yeah, more than possible. The 8.1 is a badboy, I have an 01 3500 crewcab, but a properly built 454 and a turbo 400 will match it without any problems. I have an 81 with a 540hp 468, that will pull anything the 8.1 will pull, and then some, but realistically, a mild built 454 with around 350 hp will do the same work as the 8.1. I like the Allison as well, but the turbo 400 works well if you have the truck geared for the job intended, meaning you dont put rock crawler gears in a truck to run up and down the highway. You can even build a 700r4 or even better, a 4l80 to put in it and do even better.
   Welcome to the site by the way, glad to have ya. You will get your questions answered here no problem.

[Captkaos]

1/2 vs 3/4 frames are taller and thicker, they are the same as 1T frames.

[joesgarage71]

3/4 ton frames are about .040-.050 thicker than 1/2 tons, other than that they are the same.
 I'd go with the 427 and the 465, assuming you have 3:73 gears that combo should pull that trailer around good you just wouldn't have OD

[sclark81]

3/4 ton frames are about .040-.050 thicker than 1/2 tons, other than that they are the same.
 I'd go with the 427 and the 465, assuming you have 3:73 gears that combo should pull that trailer around good you just wouldn't have OD

That's the plan!  But I have a dilemma...I bought an 83 3/4 ton 4x4 yesterday (or at least that's what he told me it was).  It's a rolling chassis with a 350, 4 speed, and 205 case.  I have it sitting right next to my 1/2 ton 2wd frame and I can tell it is thicker.  It has 7 leafs in the back as well.  The odd thing is that is has a 10 bolt front end and a 12 bolt rear??  I thought all 3/4 tons were 8 lug?  I gave $500 for this and an additional dana 44 front and 14bolt FF rear.  My dilemma is this.  I have a guy that's offering me $400 for the d44 and 14bolt.  I could sell those and by the drop kit for my 2wd and get it going.  Since the "supposed" 3/4 ton is just a spare in case the 02 craps out out, what are some opinions on just running the 10 bolt front an 12 bolt rear with the 427, 4sp, and 205?  All I'm doing is an add leaf on the front and rear and running 33x12.5 tires.  Would those axles hold up to towing in case I need it or should I just stick the 8 lug axles under it and run those?  If I thought I could get $400 for the 10 and 12 bolt combo I would, but I highly doubt it.

[joesgarage71]

 What are the gears in the two sets of axles? Keep the set that has the gears you want. 10/12 bolt set should be fine and will do what you are planning to do. sell the 44/14! 400 is a good selling price. the 44 must be a big bearing axle and have flat top knuckles, for that guy to offer 400.

[sclark81]

Both the axles on the frame I bought and the 8 lugs are 3:73s.  I think I'll just sell the 8 lugs since this is a backup truck.  It's not like I tow all the time anyway. 

[choptop]

The only thin I can see you would benefit from using the 3/4 ton parts  depends on the tongue weight of the fifth wheel. It may be pushin the limit of the carrying capacity of the 1/2 ton, but if your going to use the 3/4 ton stuff, why not use the whole suspension frame and all. Just move your body and engine over and call it good. its not going to make that much difference since both have 373 gears. The bearings on the 1/2 ton axles will thank you, plus you will have the larger brakes for stopping power.

[N2TRUX]

Something that no one has touched on here are the brakes. Even though you don't need the 44/14 for wheelin, your building this as a tow rig and you will need big brakes. Unless you plan to add aftermarket upgrades on the 10/12 combo you are not going to be happy with the stopping power, or lack there of.

I would consider running the 44/14 combo and setting it up with hydro-boost. You will thank your self later....

[choptop]

............................... plus you will have the larger brakes for stopping power.

Uh huh

[N2TRUX]

Sorry bro. I skimmed the verbage and missed your parting line there. Oh well, my intentions were good...

[choptop]

Just giving you a hard time, no worries

[joesgarage71]

your building this as a tow rig and you will need big brakes.

 Thats why they make trailer brakes.

[N2TRUX]

Thats why they make trailer brakes.

You ever had your trailer brakes stop working? It's an eye opening experience if your trucks brakes aren't up to the task....

[joesgarage71]

 Nope never did! But then again I don't drive/pull junk. I don't overdrive my equipment beyond its limits, and I always check my equipments condision.