Towing Capacity 1972 k20

[Awann99]

Howdy.
I've dug around online and can't find an exact answer for what these trucks can tow on paper.
I'm looking into a dry 8600 pound camper for work travel.
The k20 just had 3390 pound rear leafs installed and 1100 pound front leafs. And new kyb shocks. Brakes have been gone through. Does this setup sound feasible to pull something that big safely? I do have a brake controller installed as well.

The truck has a Qjet, basic crate goodwrench 350 and sm465 and 4.11 gears. 235/85/16 falken wild peaks.
I've pulled 6000 pounds easily with the truck long distance. I rebuilt the cooling system before the first trip.
Any tips or trick or suggestions for this kind of hauling would be great.
Thanks.

[connorm]

With a 72 having disc brakes, a K20 you should have a thicker frame you should have more towing capacity. The first link is really good on Post 7 Factorystock posted some good frame thickness comparisons. These trucks didn't have actual towing ratings, just GVWR. This makes it a little harder to truly gauge the towing rating. An 8600 lb DRY camper seems like a lot, especially when you load it. The trailer brake and 350/sm465/4.11 should help, along with the upgraded cooling system. The trailer brake is the biggest factor in my mind with the old brakes. A lot of it comes down to how competent you are with a towing.

https://67-72chevytrucks.com/vboard/...d.php?t=629019

https://www.67-72chevytrucks.com/vbo...d.php?t=825881

[57taskforce]

Frame thickness is a little different with the K trucks, basically GM made a long bed and a short bed frame. 1/2 ton long bed and all 3/4 ton K trucks used the same frame, with the suburban being a variant of the long bed frame. Blazer is a variant of the short bed frame. The long bed/suburban frames are thicker than the short bed/blazer frames. The main difference between a 1/2 ton long bed and all 3/4 ton was springs and axles. All that said, I don’t think I’d be scared of that setup if your truck is in good mechanical condition. The GVW on the K20 is usually 7200lbs if memory serves me. I’m 150 miles away from mine or I would verify. Remember GVW is the max weight the truck on its own should carry. Gross Combined weight is the truck and trailer together, i really don’t know what that rating is for These trucks but again I don’t think I would hesitate to pull 8600 lbs in one of them in good condition.

[Awann99]

Originally Posted by 57taskforce

Frame thickness is a little different with the K trucks, basically GM made a long bed and a short bed frame. 1/2 ton long bed and all 3/4 ton K trucks used the same frame, with the suburban being a variant of the long bed frame. Blazer is a variant of the short bed frame. The long bed/suburban frames are thicker than the short bed/blazer frames. The main difference between a 1/2 ton long bed and all 3/4 ton was springs and axles. All that said, I don’t think I’d be scared of that setup if your truck is in good mechanical condition. The GVW on the K20 is usually 7200lbs if memory serves me. I’m 150 miles away from mine or I would verify. Remember GVW is the max weight the truck on its own should carry. Gross Combined weight is the truck and trailer together, i really don’t know what that rating is for These trucks but again I don’t think I would hesitate to pull 8600 lbs in one of them in good condition.

The camper tongue weight is only 860 pounds. So it wouldn't overload the GVW. I'm an hoping the fresh suspension helps it out. The truck originally had the g60 or g50 heavy duty springs. Not sure what that added exactly but those springs are swapped out now for bigger ones. I will probably reinforce the rear frame where the towing linkage is for extra security. The posts above had a lot of good documentation.

[LS short box]

I assume you are using a rear frame mount hitch with an equalizer bar setup? Make sure your hitch frame mount is rated for the increased weight.
Have you considered a goose neck type trailer with the proper bed mount. Seems like a lot of the larger RV's are goose neck type?

[PbFut]

Truck will easily handle the tongue weight. With good trailer brake and front disc, braking will be OK. I would be concerned with the converter and tranny heat if you don't have extra cooling set up. I would find a good to rather large tranny cooler. And maybe the Delran tubed pan as well. I am not a auto trans guy normally but recent issue with a need for high stall converter tought me a few things. Most will say to run fluid through radiator cooler and then into aftermarket cooler, then back to tranny. I disagree. The radiator will warm the cold fluid, if need be, then go to trans. Radiator after aftermarket cooler will also assist if aftermarket is not cooling enough. This also protects radiator by not sending super heated tranny fluid in and over heating coolant. Works very well on my set up.
Edit: You may want to run 4 temp guages. Engine oil, converter at the exit of tranny, another in tranny pan, and finally a diff sensor. You can see problems way before it's critical this way. It gives a nice piece of mind for me

[Awann99]

I have considered the goose neck style. But they are usually about 8000$ more for the same features of a pull behind. I do have an equalizer hitch. I need to upgrade the frame mounted hitch to carry the 8600 pounds. The truck has a sm465 so I have the granny low and I don't think I need to worry about it over heating? But the extra gauge set up for the rear diff is a good idea.

[57taskforce]

What rear does it have? If it’s an Eaton you shouldn’t have to worry about a temp
Probe. They are tough as nails, same with the SM465 and NP205. Make sure they have good oil in them and you’ll be fine.

[Ol Blue K20]

My car trailer is rated to carry 12,000#. I have towed several 4x4 backhoes with front bucket with no problems. I do have a big block though.

[Awann99]

Originally Posted by 57taskforce

What rear does it have? If it’s an Eaton you shouldn’t have to worry about a temp
Probe. They are tough as nails, same with the SM465 and NP205. Make sure they have good oil in them and you’ll be fine.

It has a Dana 60. In the future I plan to swap squarebody k30 axels on it for extra strength.

[Awann99]

Originally Posted by Ol Blue K20

My car trailer is rated to carry 12,000#. I have towed several 4x4 backhoes with front bucket with no problems. I do have a big block though.

A big block does help out a lot. I might end up going that direction in the future. What kind of gas mileage do you get unloaded in that truck?

[Ol Blue K20]

Originally Posted by Awann99

A big block does help out a lot. I might end up going that direction in the future. What kind of gas mileage do you get unloaded in that truck?

I have 4.10 gears and 32" tires. If I keep it around 65mph it gets 12 to 14. I get a lot of smiles to a gallon though.

[57taskforce]

Originally Posted by Awann99

It has a Dana 60. In the future I plan to swap squarebody k30 axels on it for extra strength.

Personally, That’s one of the best upgrades you’ll do if you use it as a truck. I’ve got a 14 bolt and a front dana 60 under mine and couldn’t be happier. The extra unsprung weight of the front 60 down low really helps with the feel of stability in the truck when pulling or hauling. The Dana 60 is ok, it’s good because parts are available but it’s not quite as strong in my opinion as the eaton or its younger 14 bolt brother. Regardless of the rear axle I’d still give it a try if I was you. These old trucks are pretty capable. Just use common sense and it will be ok.

[connorm]

Originally Posted by Ol Blue K20

I have 4.10 gears and 32" tires. If I keep it around 65mph it gets 12 to 14. I get a lot of smiles to a gallon though.

12 to 14 in a K20 with a big block is great! I have a c2500 with a 307 with 4.10 and 33" and my last trip at 65 mph got me 13.5 mpg. My truck is fairly worn out, is yours a fresh rebuild? I'd like to 4x4 swap mine but I've always heard 4x4's get single digit mpg and that has always kinda turned me off

[jeffahart]

I towed heavy weight behind my K20 for years. It had front Drums back then. No issues at all. My only two cents is turn the AC off in the summer going up long steep grades. I always did this, don't know if I really needed to but I did. The Grapevine in California was a engine killer back in the day. It trained me to cut the AC off. I too think you're fine.

Have fun!

j