Gooseneck fifth wheel and a flat bed. Help!

[Deeregreen85]

Hello, I'm a little green on this so please have patience with me. I have an 1985 Chevrolet K20 that has been converted to a 1 ton truck with single rears. It has a flat bed and is set up for a gooseneck which I use quite often. We have a pop up camper now and my wife is wanting to upgrade to a fifth wheel. I have done enough research to know that there is conversions for this as my hitch ball sits below bed level. This is a gas truck with a pretty heathy 350 CID engine that I built mildly to tow with. With that being said this is not a Cummins or powerstroke. I am looking for someone that has some knowledge of these trucks and has a decent wealth of knowledge as to what these trucks are capable of camper wise. By the way, it may pull it but I also want to stop it when the time comes. Thanks and god bless.

[burningman]

Nice job! When most people say they converted a 3/4 ton to a one-ton all they did was put more leaf springs in it. You actually put EVERYTHING in (expect maybe the hydro boost brake system?) and anyone who really knows trucks knows you DID substantially increase your GVWR. The hard parts are all there. There will always be the guy who says if the factory didn't do it, it didn't happen.

I've done all that stuff a few times myself. One of my old trucks was a Ford that carried a camper and towed a boat with plenty of power (a very "built" '68 428) and it was also a 4-speed and 3.50 gears, similar to your truck. That truck was right in the happy zone empty but the gearing sucked under a heavy load. The jump from 3rd to 4th was just too big and I had a hard time holding 4th up hills under a big load... and I had a LOT of horsepower. Gas motors just don't make their power at low enough revs to use tall gears with heavy weight. I swapped the entire chassis of that truck for another using 4.10 gears and it was a much better heavy load rig. It used to spank all the diesels about 17 years ago. (Not now!!!)
Your rig sounds perfectly up to the job, all except those tall gears.
The transmission will handle it, that K20 would have come with the same SM465 my '86 K3500 dually has.

I've had a 14,000 pound load (camper plus trailer) on my '86 GMC many times over many mountains without issue. Sure it's a little slow, but it gets there. And unlike a more powerful modern truck, if something does go wrong, you can open the hood, see it, and fix it easily and cheaply! But mine is a 454 with 4.10s.

I have a friend who carries a very heavy 11.5 foot camper and tows an enclosed trailer full of snowmobiles over the mountains with a '77 Chevy 4x4 crewcab dually with a 350 and 4-speed but he has 4.10s. And he's looking at doing a 383 stroker.

If I had to choose between the truck with the 350 and 3.42 gears and the '97 7.3 diesel, I do think I'd use the diesel.

[canuck_1]

use the truck. Add an ht502 crate motor and it would be a perfect rig. My 76 dually works well with 18500 behind it

[Deeregreen85]

Sounds to me like I need to scrap the idea of using the K20 and drag the powerstroke out. From my measurement at a local RV sales lot, I need to stay under 30' regardless due to my shed. If I get over 30', not only will I be buying a camper I will be adding on to my shed also. That being the case it is a 1997 OBS ext cab long bed f-250 with the heavy service spring package and the 7.3 turbo diesel. It is bone stock, nothing ever done to it performance wise. Still has the stock intake and exhaust. I know I have had a combined weight of trailer and load at 14K behind it and I know that I don't want to do that EVER again. Just a little piece of advise and I am sure I am preaching to the choir on this one, do not let family talk you into hauling stuff for them. There was a lot of lost religion when I got home.

[mkirsch]

The 4-speed doesn't help. 3.42 gears are a problem, limiting you to ~5000lbs of towing, if I'm not mistaken, and then not very comfortable towing. Lots of time down in 3rd (really 2nd because of the granny low).

On an old school truck like that you really need 4.10 or even 4.30 gears. This will get the RPMs of the engine up so that you can tow. Even then you're probably only looking at 8000lbs if you want any comfort level at all. That's a pretty small 5th wheel.

With newer trucks the gearing isn't so much of an issue because you have more gears to choose from, and more evenly-spaced. On your truck there's such a gap between top gear and the next one down...

[Deeregreen85]

Well the upshot of that is that the truck has a 4spd instead of the turbo 400. The Biggest question I have is that fact of what weight campers I should be looking at. I am not scared to drag my powerstroke out of retirement if needed but I would prefer not to. My wife is the one that wants a fifth wheel and I would settle for what ever. Does not make a difference to me s long as it has and outdoor kitchen. Yes a I know that is a sad request but a man has to have his say.

[JIMNLIN]

Lots of blank spaces on what your truck is and what was done to it.
The trucks gvwr won't change nor will you get state certified vehicle modifier to change the trucks gvwr.

Those 3.42 gears are not a good gear for towing heavy trailers and will limit you on the 5th wheel trailer size/weight. As far as dot/insurance is concerned its still a 3/4 ton truck.

No doubt a built for towing 350 and a built for towing Th400 tranny with a big aux cooler won't have any issues.

As another poster says you won't have tail wagging the dog with a 5th wheel trailer like a bumper pull. Apples vs oranges.

I would stick with a 10k gvw trailer...mostly because of the tall 3.42 gears.
Now go with some 4.10 gears/suspension/brakes/the whole works from a late model one ton srw truck can give you another 2k-4k gross weight trailer.

[Deeregreen85]

I have no problem my self pulling the camper of any type. I normally drive a 379 peterbuilt exthd daily with a detach low boy. I want to make sure the truck I want to pull with will handle the weight of a fifth wheel camper.

[lc0338]

a fifth wheel pulls much better than a bumper pull. I don't believe you will have to worry about trailer sway. If the trailer has brakes on it and you look WAY down the road for any trouble ahead you will probably be just fine. Extreme defensive driving while towing will usually keep you out of trouble 🙂

[Deeregreen85]

It did start with the 11" brakes on the truck. I removed a 1-ton single wheel rear with 13" brakes from a donor truck and used the springs from it. I have also added a little more spring to it as I have a close friend that runs and automotive spring shop. This is an odd truck as it has a 4spd with a 3.42 gear. it is a K20 and I have installed a Dana 60 front axle due to it having a 10 bolt factory axle. I have know clue what the gvwr is on the truck at this point. I know that with my 26' deck over gooseneck with my 240 skid steer the truck squats about 2" versus my '97 powerstroke that squats about 4.5". I built the truck to pull with and be able to use on the farm, the truck drives good enough I would just assume to pull a camper with it than I would my powerstroke. The issue I am running into is I have only pulled bumper pull campers. Never hooked to a fifth wheel, the camper I pulled was from Raleigh NC to Yadkinville for my cousin. I did have a weight distribution hitch and a sway control but with this truck being a single cab long bed from the factory it did ok but did not like the 32' travel trailer on the highway at 65-70 MPH. I don't want to have a fifth wheel that starts the old saying of the tail wagging the dog.

[eHoefler]

I have extensive knowledge in the 70's-80's GM pickups, I am curiouse to what was done to convert your 3/4 ton to a one ton. At best, the 3/4 ton would have a GVW of aprox. 8,400 pounds, this is if you have the 13" rear brakes. Most where 11" brakes which only had a 6,800 pound GVW. Also, if you are 4 wheel drive, and have the 6,800 pound GVW, the springs and front axle is the same as the 1/2 ton, just different hubs and rotors.

[lc0338]

Found this pdf showing specifications on c/k chevrolet 1986

https://www.gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/Chevrolet-Trucks/1986-Chevrolet-Truck.pdf

[lc0338]

forgot to mention... my 3 horse living quarter trailer is a regular gooseneck type hitch. I still own a neckover stock trailer with a gooseneck hitch. Will never go away from that type of hitch because it frees up my bed when not towing 🙂

[lc0338]

Deeregreen85 wrote:
Thanks for the information. Have you ever had any experience with a flat bed conversion to a fifth wheel?

No, I know they are available. I have towed gooseneck trailers all my life. Now have a 3 horse living quarter horse trailer and a 5500 RAM 2014 year model with a cannonball flatbed trailer on it.

Here is a link to etrailer conversions:
https://www.etrailer.com/faq-adapting-a-5th-wheel-trailer-to-gooseneck-hitch.aspx

[Deeregreen85]

Thanks for the information. Have you ever had any experience with a flat bed conversion to a fifth wheel?