81 k20 vs 86 k15 frame and axles

[mythicfab]

I work at a junk yard and was able to buy a 1986 gmc k15 short bed for a 300$ it has a cracked frame and the point in the frame that the shocks mount are all worn out. Only thing it was missing was the engine which was fine with me because I have a spare 6.0 laying around. I've heard that the original 6 lug axle doesn't like the power of the 6.0 and like to self destruct but I've also heard of people running them just fine. I was original just going to weld up the frame maybe try to reinforce it a little and send it but then I ended up with a 1981 chevy k20 long bedcamper special. The truck runs and drives but the cab is shot. I still would like to do a 6.0 as the truck is for my girlfriend and wants a little better fuel mileage. Short story long I don't know what would be the easiest and the safest to just weld and reinforce the k15 frame or shorten the k20 frame and run the 8 lug axles. Ive also got plenty of spare 5.3 if they would be better to run with the 6 lugs.

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[Chevy 88]

Really cant see anything about the frame in the pic. Can you sand blast or pressure wash it and send new pics? Need to see the metal, but all I can see is mud/undercoating.

 

[mythicfab]

Really cant see anything about the frame in the pic. Can you sand blast or pressure wash it and send new pics? Need to see the metal, but all I can see is mud/undercoating.

Best i can do at the moment is a new angle. It's been welded once on the outside of the frame rails it was extremely poor welds. Now the gap in the bed and the cab is all sorts of screwy.

 

[Chevy 88]

Ah.

Well, its still hard to tell a lot when its dirty, but if those are cracks, and not just cracked mud or undercoating - then I would say wending would be needed. Not too difficult of a job. Just make sure your fuel tank is 100% full before welding back in that area.

 

[mythicfab]

Here's some other pictures of the k15 frame problem areas not major but an annoyance none the less. Picture of the whole is original shock mount for driver side. The one with the nut sticking through a hole is a custom shock mount behind the rear axle on the passenger side.

 

[mythicfab]

Ah.

Well, its still hard to tell a lot when its dirty, but if those are cracks, and not just cracked mud or undercoating - then I would say wending would be needed. Not too difficult of a job. Just make sure your fuel tank is 100% full before welding back in that area.

Agreed, I could have the crack welded up in no time I just worry that with all the frame damage everywhere, although extremely common in the old k10s is worth reinforcing compared to just shortening an already good frame. Plus if the 6 lug axles can't handle the power of a 6.0 i wonder if I may as well use the 8 lugs that are already connected to a heavier duty frame.

 

[Chevy 88]

Well, you could just add 20 LBS of metal. Might look terrible, but the next buyer will never crawl under there to check it out. And since it will be reliable anyway, whats the harm.

 

[legopnuematic]

A 1/2 ton and 3/4 ton squarebody frame are basically the same, depending on year/configuration some minor things like crossmembers may be different. Thickness between them should be more or less the same. Except for a C/K30, those are quite a bit heavier of a frame and are 8" rails vs 6" rails.

Both your K10 and K20 will have a 10 bolt front axle, the hubs/brakes are different, but are both an 8.5" 10 bolt. The rear of the K10 is a 8.5 10 bolt as well, the K20 appears to be a 9.5 semi float 14 bolt.

The 9.5 is a fair bit beefier of an axle over the 10 bolt rear.

A stock or near stock 6.0 LS would probably be fine in front of the stock 10 bolt for normal/mild driving. Really would depend on your intentions for the truck.