Author Topic: How are medium/heavy duty trucks different than my 3500?  (Read 9510 times)

Offline bryanedp9

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How are medium/heavy duty trucks different than my 3500?
« on: October 20, 2017, 08:40:58 AM »
As the title states, I'm curious, especially for the frame and suspension. I know the firewall is different but that's about it. Is the frame taller altogether?

I'm not trying to make a monster truck, but I'm thinking about stretching my frame to get a rollback-esque kinda flatbed that I can put a huge camper on. Like I'd like to be able to carry the weight of the truck on the truck, essentially, rather than the stated 3500lbs I think it is? I've even considered a third axle, but that seems like overkill. The truck is a '89 CC dually with a 454/400 that I'm trying to swap for a 6.5/4500 at the moment, which would be just economical if it weren't for the weight I'm anticipating.

I'll almost certainly need to stretch the truck at least a few feet, and the budget says it's probably gonna be a steel bed. I'd like to try to go light building the camper with wood or aluminum, but it would be easy enough to convert a 20' shipping container or a horse trailer, it seems. The shipping container would be in the neighborhood of 5-6000lbs empty.

The cab itself is kinda dear to me, but since this is either a fantasy or way-off, let's assume I could ditch everything else. Do I really need to, or can I stretch my truck and beef it up a bit and voila? I'm assuming either is possible but a cheap old Topkick could save a lot of headache, as well. Thoughts?

Offline bryanedp9

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Re: 3500 vs Topkick, differences? Buy or modify?
« Reply #1 on: October 23, 2017, 09:40:16 PM »
Okay, maybe this should be moved up a few forums? Or does nobody know? I'm trying to suss out the differences through pictures but I'm still unsure about the frame rails.

EDIT: One thing I did find is that the payload seems to be 4,689 pounds according to some handbook from the heritage center. I'm already in the ballpark but I'd like to be able to load essentially a spare ton in the very back as the intention here is to build a toyhauler of sorts that would fit my Willys or the car, not to mention a motorcycle or two, and so on... I can snag a beat up c60 cheap enough I may have to just do so.
« Last Edit: October 24, 2017, 12:12:21 AM by bryanedp9 »

Offline bryanedp9

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How are medium/heavy duty trucks different than my 3500?
« Reply #2 on: October 24, 2017, 06:16:32 AM »
Mostly curious about, obviously, the brakes, frame, steering & suspension. Especially the frame and suspension. I posted in the crew cabs section but have since realized it's not really applicable there. Although I'm considering giving my crew cab about twice the payload, this is a better place to ask. I'm trying to find documentation on the bigger trucks from this era (mine's an '89) but even the ton trucks seem to be hard to find info on, let alone the bigger ones.

Trying to see (obviously the spring perches are different) if the frame is different. The cab & chassis ones seem to be spaced uniformly for the boxes and whatever may be put on, but I'm not sure if that applies to all or just some of the larger trucks. Also not sure about the size of the rails.

I'm even considering a tandem axle, but trying to keep total length around 25' so it may not be necessary. I can find the big trucks cheap, but I'm still on the fence about if/how I should attempt to stretch my truck, or throw its cab on a bigger one, or do some mixing and matching. For instance, if I let this guy keep the chipper bed, I can have an 80's C60 with a nonrunning 360 in it for $500. But I've heard the C60 and maybe C65 aren't really that much tougher than a 3500. Still yet, a C70 is still cheap to come across, hopefully in the length I want.

Any info or tips would be greatly appreciated.

Offline Irish_Alley

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #3 on: October 25, 2017, 09:15:20 PM »
im kind of lost on what your desired outcome is. what are your plans for the usage of this truck? if you give your crew cab twice the payload you would need to have it certified,tagged and insured along with having your CLDs (a dually crew cab 4x4 with 454 and th400 is around 11000 gvwr if memory is correct.)

 
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Offline Irish_Alley

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #4 on: October 25, 2017, 09:22:33 PM »
ok after finding the other topics and merging them i see what you want. i know my curb weight is around 7300 in my 91 v3500 crew srw with the cummins and 4l80e, yours should be a little less. so your payload is about what you posted. that being said 4k of extra weight in the bed i wouldnt trust it. i would get a trailer or build one that could do all you want and still stay legal
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Offline bryanedp9

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #5 on: October 25, 2017, 09:38:06 PM »
My understanding was if I keep GVWR under 26k I can avoid the CDL. Still if it got that big I'd consider air brakes and a tandem axle, and I think air brakes requires a CDL here. I'll have to brush up on that.

Seems like I could hack a medium duty frame to stretch my own if needed, but that's the kinda stuff I'm still curious about. As mentioned, I may have to just find one at some point.

Saw the strangest thing on the highway a couple weeks ago, a GMT400 with about a 15' wooden flatbed trailer where the bed should be. Looked like the frame was even lowered for it, and had a ramp back. Kinda up my alley.

But for my idea I'm assuming just shy of 10,000lbs payload (heavy camper, vehicle, furnishings, tools, people), plus the 7000 or so the truck ways, for a 17k GVWR or so.

Offline Irish_Alley

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #6 on: October 25, 2017, 10:24:32 PM »
yes anything 26001 or above you need a CDL. your axles arnt rated for anything above your gvwr so you wont be able to use them afaik along with your brakes. truck length will be next thing to deal with. i dont know if there is any limit to how long your truck can be but since we covered your axles and brakes are no good you have to put new axles/springs and prob frame under your truck.

since your doing that your better off with getting one of those kodiaks like you mentioned
http://www.pirate4x4.com/forum/tow-rigs-trailers/1079688-topkick-kodiak-cab-vs-1-2-ton-cab.html

but then you still have to stretch the frame just to fit your jeep. a trailer would be much more feasible
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Offline bryanedp9

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #7 on: October 26, 2017, 04:27:46 AM »
yes anything 26001 or above you need a CDL. your axles arnt rated for anything above your gvwr so you wont be able to use them afaik along with your brakes. truck length will be next thing to deal with. i dont know if there is any limit to how long your truck can be but since we covered your axles and brakes are no good you have to put new axles/springs and prob frame under your truck.

since your doing that your better off with getting one of those kodiaks like you mentioned
http://www.pirate4x4.com/forum/tow-rigs-trailers/1079688-topkick-kodiak-cab-vs-1-2-ton-cab.html

but then you still have to stretch the frame just to fit your jeep. a trailer would be much more feasible

I agree about the feasibility. Still curious about specific frame differences, i.e. could I just take the axles and suspension from a MDT or is the frame that much bigger? Or is it the closer spacing of the rails that helps so much?

The reasoning for trying to avoid a trailer is simply maneuverability in traffic and potentially offroad. Although you could say the same thing for the trailer itself in a hairpin, couldn't ya? However in tight loading and unloading situations, especially backing in, a bed or box is a bit easier to wrangle, especially vs using the ball hitch on a CC truck or something long like that.

Not to mention, I like the idea of actually just making it a rollback with the camper on it. Dismounting a heavy box would be a bit easier with a winch and a tilting bed, maybe some rollers, as opposed to the jacks that usually come with those truck campers. I'd need some heavy duty solution unless I wise up and try to build it out of lighter materials. With the right hydraulic setup I could have a scissor lift or rollback. Also begs for a lighter camper if I wanna try skyjacking it. A shipping container as heavy as the truck with that much leverage in a stiff wind...

Offline Irish_Alley

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #8 on: October 26, 2017, 11:21:23 AM »
The idea of it seams like it would be very cool. But the audience here I think won't be able to help you with those details. I would try pirate 4x4 you will have a much bigger audience that should be able to help you. But keep us posted on what you find and I know I really would like to see this build
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When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline bryanedp9

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #9 on: October 29, 2017, 08:43:45 PM »
I'll give that forum a try. Really just tired of registering somewhere every time I get a project idea haha. I appreciate the interest and I'll let ya know how it goes.

Offline roundhouse

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How are medium/heavy duty trucks different than my 3500?
« Reply #10 on: October 29, 2017, 08:56:57 PM »
Pirate is a great place to read up on custom modified trucks

The tow rig section would be a good place to start.

THere are some awesome expedition rig builds on pirate in their expedition rig forum

I will warn ya though
Read a lot and use the search box

Pirate is not the place if you have thin skin ,
They will flame you for asking a question that could be found using the search box

What you're describing , you need to just get a truck that's more suited to what you want to use it for

Although a shipping container would be really really too heavy

A normal cargo box with fiberglass sides  would be a good place to start

Crew cab 4wd MDTs are not too hard to find
Just pull off the power company cherry picker and add your custom built camper
It would need to be custom built because all store bought campers are total crap
The floor plans are terrible and the materials are entirely too flimsy
   I'd start With a U haul box or something like it and build a camper


Also what exactly is going to be the use for this vehicle ?
I assume you'd want 4wd but you didn't mention it

And I'm pretty sure you're exempt from any CDL regs as long as it's registered as a motorhome
Which is pretty easy in most states , you can get a 10 wheel peterbilt tractor registered as a motorhome RV if it has a microwave , fridge and portapotty and wiring for shore power


There's a site called
Expedition portal that had a lot of cool builds
« Last Edit: October 29, 2017, 09:28:04 PM by roundhouse »


Offline bryanedp9

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #12 on: October 30, 2017, 03:52:06 AM »
I'm actually a member over at expedition portal. I've got a little thread mentioning some of this there. Also the Blazer Chalet is awesome. There was one for sale locally awhile back.

I agree that most campers are just too cheaply made for my purposes, but the box truck boxes would need extended for the crew cab on most I've seen. I suppose if they're just some steel, plywood and fiberglass it wouldn't be too hard to extend. I need to get a look inside more of them, but the corner framing seems inadequate for mounting jacks to dismount the camper, especially if loaded with a vehicle. The floor structure itself is another thing to consider for mounting/dismounting and vehicle loading. Still may be a good starting point.

So most of the ideas seem either too flimsy or too heavy.

Offline roundhouse

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How are medium/heavy duty trucks different than my 3500?
« Reply #13 on: October 30, 2017, 09:29:21 AM »
You want to haul a vehicle inside the camper and be able to dismount the camper with the vehicle inside ?


Like a jeep or dune  buggy or what kinda vehicle we talking about ?


That's gonna require a Heavy truck and lighten you wallet
I'm sure there are some commercial or military trucks that can self load , but the big question is why ?

« Last Edit: October 30, 2017, 09:43:52 AM by roundhouse »

Offline roundhouse

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Re: How are medium/heavy duty trucks different than my 3500?
« Reply #14 on: October 30, 2017, 09:30:10 AM »
Contact this guy on pirate and see if he knows who manufactured the box