K20 pulling 19k lbs...

[Dano500]

Gasoline will be extinct before "this sounds like a good idea" comes to fruition.

I guess we shall see about that one. lol

 

[Bextreme04]

Yup, it is a 5th wheel trailer. 15.9k dry weight & 18.9k gross weight, which includes 1k lbs of fresh water and 2k cargo. I was looking at a 3500 RAM before, but not interested in spending $60k.

I've seen this truck with 454 towing 14k lbs, which is what gave me the idea.

My first thought on reading this is that you have lost your ever loving mind....

There is no difference between a 3/4 and 1/2 ton frame in the squarebody trucks. If you have a C6P option then the frame is made from a slightly thicker material. The 1 ton frames are ~1" taller C-channel. If this was a crew cab truck, then it would be the thickest and tallest frame and might be able to hold up to that kind of regular load.

I would be VERY concerned that you might fold the frame up with that kind of constant load on it.

What rear axle does the truck have now? I know most of the later 80's K20's got semi-float 14 bolts... mine is a high GVWR one, so I have the 13" drums and a 14BFF. I've got a mildly built 350 in it now and it has a hard time with the 6500lb travel trailer. I'm swapping in a fuel injected 454/4L80e combo, at which point it should tow the 6800lbs with eases, but I would NEVER consider hauling 19k with it at anything above a crawl for a few miles on back country roads.

 

[Dano500]

The trailer my mom, brother and I live in is a 40' long, 12' high fifth wheel, triple axle. The friend we got it from lives in Conroe and the trailer was in Splendora. He moved it from where he got it, to his shop and property, and then brought it to the RV park in SW Houston near 610. For all of this, he used a RAM dually one ton 4x4 with a Cummins in it. Our trailer weighs around what yours does, maybe a little more. I remember him mentioning 15K# in the discussion about getting and moving it.
That truck moved this trailer just fine. I've also seen him move loaded car hauler trailers with the Cummins powered dually he had before this one. He used to drive semi's and goes all over the South, buying and selling cars. So he's used to hauling heavy loads and knows what it takes to do the job.
My one ton crew cab would probably (if it had the appropriate hitch) move this trailer, but not near as well, and it probably wouldn't do it for a long distance. Certainly not near as well as a dually would. And unless it's an emergency I'm not going to haul way more than my truck will handle!
A few months ago, we went on a trip to Austin and back, to a big car show and swap meet. The truck had the 3 of us and gear for a long weekend in the back seat (including my tools which is 100# right there) and the bed was full of tables, parts and fixtures for my booth. We were towing a 5x8 enclosed utility trailer, that was full, probably 3600# total, trailer weight and contents. This combo would go all day on flat ground at 65; once we got into the hills it needed a little more throttle to keep that speed. The truck performed well on the trip, but I noticed that the extra weight did require a good bit of extra stopping distance. And this is a full floating axle, GM 14 bolt, 10.5" ring gear, with 13"x3.5" rear brakes and big discs up front. We weren't asking the truck to do anything it's not built to do, but even the small trailer we were pulling, would push you down the hill on a stop. Just basic physics there. Getting a large heavy mass moving takes some distance and effort; so does stopping it!
Last year at the park, a guy came in hauling a trailer almost as big as ours, with a '93 GMC one ton dually. He said it has a 454 in it, and he pulls this trailer a lot with this truck, and he'd just come from Florida with it. Only places he had trouble towing it was in the tunnels around Mobile, and I know those are steep grades. I bet the running gear isn't stock though! Didn't get a chance to find out more on this, because we were heading out of town, when we got home, he was gone.
There's often many newer 5th wheel and large bumper pull trailers here in the park; all are pulled by late model one tons, mostly duallies. A few of the 4500/5500 medium duty tow rigs too. These are just better designed for hauling the bigger trailers people use nowadays. When the squares were new, even when the OBS trucks were new, the trailers weren't as big, tall and heavy as they are now. It's not just about engines, transmissions, brakes and axles; the frames and suspension have to be stouter too.

Hello!

Yes, I have been looking into modern 3500 pick ups, particularly RAM, so everything is still on the table, I just think it can be done and I enjoy proving people wrong. lol It really comes down to basic math. How much power is needed to move the 25k lbs safely down the highway and how much is needed to stop it (yes, with stability). The truck won't be a K20 anymore because everything that matters in this scenario will be bigger, stronger and better except FRAME STRENGTH and that is what is most concerning. I don't know what differences are between K20 frame and K30 frame, BUT tongue weight is 2,8xxlbs and I'm hoping the payload capacity for truck is 4k, but I an't find any info.
I do know the leafspring pack is 8 and they are 56" long and from what I have found, that should put payload around 3,500 to 4,000lbs.

Question: When this K20 was new, how would it have affected tow capacity if the only difference would have been
switching the 175hp/275tq 350 sbc to 400hp/550tq 500 caddy? I bet the increase would have been BIG
What about bigger brakes, transmission, suspension?

I'm going to proceed with the build anyway, at worst case, I will have a pretty awesome truck. lol

 

[Keith Seymore]

This was 15,500 if I remember correctly. I was moving it locally from one storage location to another for a friend.

I would not go very far or very fast with this set up.

K

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[Redfish]

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[Dano500]

My first thought on reading this is that you have lost your ever loving mind....

There is no difference between a 3/4 and 1/2 ton frame in the squarebody trucks. If you have a C6P option then the frame is made from a slightly thicker material. The 1 ton frames are ~1" taller C-channel. If this was a crew cab truck, then it would be the thickest and tallest frame and might be able to hold up to that kind of regular load.

I would be VERY concerned that you might fold the frame up with that kind of constant load on it.

What rear axle does the truck have now? I know most of the later 80's K20's got semi-float 14 bolts... mine is a high GVWR one, so I have the 13" drums and a 14BFF. I've got a mildly built 350 in it now and it has a hard time with the 6500lb travel trailer. I'm swapping in a fuel injected 454/4L80e combo, at which point it should tow the 6800lbs with eases, but I would NEVER consider hauling 19k with it at anything above a crawl for a few miles on back country roads.

lol You are welcome to your opinion, I understand.

What kind of constant load? The tongue weight of 2.8k lbs, which is well below the payload capacity, or the overall towing weight? I'm not being a smart ass, I really want to know your thoughts. I have the same setup as you as far as the diff and the drums. What is your 454 putting out with regard to hp/tq? The 500 cid will have 500hp and 650tq. My main concern is not enough braking power, even though the trailer has brakes to help out.

 

[Dano500]

This was 15,500 if I remember correctly. I was moving it locally from one storage location to another for a friend.

I would not go very far or very fast with this set up.

K

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Hello and thanks for your advice.

I like those tiny houses! So, if you don't mind my asking, what is the setup of the pickup? One factor I would have to help is the fifth wheel vs. the bumper pull. Again, I really think stopping would be the main concern.

 

[Dano500]

I think if you were to do it, you would need a later model 1 ton running gear (8.1l or duramax) and plenty of frame strengthening, and probably a 14 bolt FF rear and DRW conversion. At that point, you could buy either of those Kodiak's posted earlier (man, that square looks awesome ) and fix up your square as a tool-around truck. I'll give it to you that driving around Houston you aren't going to find many mountain passes, but brakes and stability for emergency lane changes will be big, and sway from side gusts will be a factor as well. I'd want as wide of a platform as possible if it was me.

Last month I took my 34' Kodiak based motorhome, flat towing my 87 Burban behind it, through Houston twice. Combined weight and combined length are probably pretty close to what you have in mind, just flipped end to end. With the C5500 chassis, it was only occasionally harrowing, but it was never pleasant. Trying to do that with the chassis of my Suburban (a K20) would scare the ever-loving life out of me, fwiw.

Hello,

Thanks for your feedback, You may be right, maybe the sway factor along with good braking and stability would make it impossible.

 

[Dano500]

That said I could be totally full of sheet and this truck is an example of someone who did what you’re proposing albeit 40 years ago when there weren’t much better options in light duty trucks.
I spoke with the old feller selling it yesterday. Turns out someone committed to buying it about 1 hour after he posted the add but I’ll be headed to MT if it’s not gone today!
GM never built this truck in the early 70s. Owner bought it from his buddy who bought it new and converted a 73 K20 into a dually and dropped a 400sbc in place of the presumably 350 factory motor. Said the guy used it to tow his tractor and the srw axle didn’t like it.
Also in Montana which = high altitude and steep mountain grades. apparently he and the truck lived through it as this is how it sat 35 years ago when it was purchased by the current owner.

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That's a nice conversion! Let us know if you end up making the trip to pick it up.

 

[Hunter79764]

I think Hp/Torque is really about the least concern. You can tow that much weight with a 235 straight 6, as long as you have the gearing. But you can't put a 5000 pound trailer with 500 lb tongue weight on an S10. even if you put a 14 bolt under it, there's just not enough frame strength, brakes, mass, steering, stability, etc. Can it be done? Sure, you see that kind of thing headed to Mexico all the time. A minivan pulling an SUV pulling a sedan. But it ain't right, and if you're going to do it right, it's going to cost about as much as buying a truck for the cause. The frame is the thing least easy to change, but it's probably highest on the list. Next is rear axle, rear suspension, cooling system (including things like PS cooling), steer axle, then transmission and at last, engine.

 

[Dano500]

Another thought, campers are still selling pretty well around here and seems for good money still, despite the absolute glut of newer campers on the market due to Covid. I expected the bottom to drop out of the camper market by now but it hasn’t although I’d be very surprised if it doesn’t next year.
I think it’s still the best time to sell a camper if you didn’t sell it in the last 2 years. And next year will be a better time to buy one, cost wise.
Unless full timing or big pimpin, I can’t imagine doing road trips with a semi trailer hooked to even a newer pickup. Far too limiting unless you’re literally running major highways to full service RV parks.
If you want to “get out and get away” a more manageable size camper is a far better option for most.
To that point, you may possibly even run the risk of being denied entry into some RV parks based on the age of your rig.
Well yes I’m still 100% of the opinion that this is not a sound plan but hopefully my thoughts are well received as I’m saying this stuff from experience.

Definitely well received and I appreciate your input, I really do. Lots of stuff to mull over, but it definitely won't hurt to proceed with the build. In any event, It will end up being a pretty nice and capable truck. I never would have bought the fifth wheel had i known it was going to require a one ton to move it. oh well. I could always set this one out on the lake somewhere and air bnb it and buy a smaller trailer to travel with.

 

[Dano500]

I think Hp/Torque is really about the least concern. You can tow that much weight with a 235 straight 6, as long as you have the gearing. But you can't put a 5000 pound trailer with 500 lb tongue weight on an S10. even if you put a 14 bolt under it, there's just not enough frame strength, brakes, mass, steering, stability, etc. Can it be done? Sure, you see that kind of thing headed to Mexico all the time. A minivan pulling an SUV pulling a sedan. But it ain't right, and if you're going to do it right, it's going to cost about as much as buying a truck for the cause. The frame is the thing least easy to change, but it's probably highest on the list. Next is rear axle, rear suspension, cooling system (including things like PS cooling), steer axle, then transmission and at last, engine.

Yup, I agree with you, the frame and braking power are most concerning. What makes me think though is the payload of pick up should be 3500 to 4000lbs, or am I wrong there? Why would the tongue weight of 2,800 lbs be a problem for folding the frame?

 

[Trucksareforwork]

Dan, you've been a real nice guy in this thread given all the very direct advice you've received. So I'll try to put this gently: If everybody tells you it's a bad idea, and that it's unsafe, and that you put yourself at legal peril, and all of that doesn't dissuade you; then what if somebody tells you that you are far more likely to kill somebody or yourself by towing a heavy load with an inappropriate tow vehicle? Because by my read of this thread, that's the only thing that people haven't told you.

Again, build the truck you want. I'm not even close to an expert on towing but I do know that the advice on this thread is consistent with US and State DOT rules that have been written in blood. Lots of it.

 

[Redfish]

Yup, I agree with you, the frame and braking power are most concerning. What makes me think though is the payload of pick up should be 3500 to 4000lbs, or am I wrong there? Why would the tongue weight of 2,800 lbs be a problem for folding the frame?

Because there is 16,000 pounds of inertia when you try to stop and when you are trying to turn and when you hit rough spots in the road. The truck may very well be able to carry 4000 pounds but that doesn't mean it can handle 16,000 pounds trying to twist it into a knot. The tongue weight (it's actually called pin weight on a 5th wheel) is not the issue.

And remember that trailer brakes will shift the weight of your trailer under hard braking. We all know that when we hit the brakes hard our vehicles go nose down. That trailer which has a very, very short wheelbase does the same thing but has more leverage to apply force down and forward under hard braking. That dynamic redistribution of forces is something that has to be taken into consideration. Will your frame and suspension be able to handle that?

I keep thinking this is really just a joke to see what responses will get stirred up...

 

[Bextreme04]

Yup, I agree with you, the frame and braking power are most concerning. What makes me think though is the payload of pick up should be 3500 to 4000lbs, or am I wrong there? Why would the tongue weight of 2,800 lbs be a problem for folding the frame?

The rated payload capacity on an '84 K20 is nowhere near 3500-4000lbs. It's a 3/4 ton... that would be an expected bed capacity in the 1500lb range. The rated towing capacity on these things back in the day was like 6,000lbs... maybe. I have carried 3000lbs of stuff in a squarebody bed but it is spread out over the entire bed, like gravel, wood, etc... I have fully rebuilt suspension, drivetrain, and heavy duty rated components and it gets super mushy and sketchy with that kind of weight in the back.

You are talking about putting a constant, dynamic, 2800lb load on two single points of the frame through a 5th wheel mount. A modern 1 ton that is designed for this kind of thing will have a fully boxed frame in that area that is probably 2-3x the strength of even a crew cab squarebody, which is itself about twice as strong as a single cab K20. I wouldn't even be too concerned with the braking part, except to consider if you happen to lose your trailer brakes you will be completely hosed at that kind of trailer weight. There really isn't anything you can do to help that though. You already have the biggest brake package available and they used that same one all the way through the early 2000's on 3/4 and 1-tons.

The price of admission for regularly hauling that kind of weight is going to start at a 1-ton if you don't want it folding in half. The braking and power side of this is the least of your concerns.