Shortening truck frame question

[3rdgendslmech]

Hey guys I've got a question, I'm not a welder by trade, but I like to think I do a pretty good job at it.
I haven't committed to the idea yet but throwing it out there to see who's done it before and hopefully get a little advice.
A friend of mine has a 95 Dodge 3500 with a 12 valve cummins and 5 spd manual. It's a regular cab with a 11 or 12' dump bed stake body. The only thing wrong with it other than its been sitting for about 15 years is the back of the cab cracked right above where the floor and cab meet.
What I want to know is if I were to shorten the frame, and put a 8 foot dually or regular bed, better part of my knowledge is to make "Z" cuts behind the cab where the frame is straightest correct? I'd fish plate the inside for extra strength but the truck most likely would not be worked hard.
I also heard some saying to avoid vertical welds???? Every fishplate I've seen and put on myself the verticals arent welded.
So that kinda throws the Z notch out the window? The only other ideal way to do this IMO is to slant cut the frame rails.

 

[bri_man57]

I saw these guys do this and really liked the style and believe it would be very strong.

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[Sevenhills1952]

I was just thinking, and I already know I'll get "you're an idiot!" comments [emoji16], but what is the 25 yo truck worth right now, especially not running 15 years. What will everything cost getting it running, roadworthy, welding time, etc., then what's it worth?
What happens if (God forbid) it's in an accident and the other party's lawyer uses the fact it was modified?
Now if it was to be used on a farm somewhere...no problem.
I don't mean to discourage, just devil's advocate.
Thanks.

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[Buckgnarly]

I was just thinking, and I already know I'll get "you're an idiot!" comments [emoji16], but what is the 25 yo truck worth right now, especially not running 15 years. What will everything cost getting it running, roadworthy, welding time, etc., then what's it worth?
What happens if (God forbid) it's in an accident and the other party's lawyer uses the fact it was modified?
Now if it was to be used on a farm somewhere...no problem.
I don't mean to discourage, just devil's advocate.
Thanks.

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1995, Cummins and 5sp answers those questions....at least for my tastes.

 

[Sevenhills1952]

I just checked Kelly. I entered 150k miles, good condition, private sale. It says $3,900

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[bri_man57]

1995, Cummins and 5sp answers those questions....at least for my tastes.

Agreed. Certain trucks you just can't get anymore. A mostly mechanical Cummins with a manual transmission is one of them lol.

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[Bigblue&Goldie]

The only value to that truck is the motor and maybe the trans. I'd pull the motor and put it in a better truck.

Otherwise, if you decided to shorten the frame the pictures posted above are the "proper" way to do it. Keep in mind, frames of that era are designed to flex.

 

[3rdgendslmech]

I personally know the truck because I did the maintenance on it from when it was brand new. I was only 12, but once the warranty was up, I did everything. Truck has just about 100K on the odometer I believe last time I looked. My brother and I fired it up a few years back when we were at his yard working on a bobcat together. I've known the guy since I was 5 years old. What I couldn't take care of my dad did. So there's a little bit of a sentimental value there. If I know I wouldn't be harassed by Md. Transit Authority for it being a flatbed I'd leave it alone. I could always stick a "not for hire" magnet on it i guess. It ended up getting parked due to when the owner updated his 2 skid steers they were heavier, and also picked up more work after adding some more springs and helpers the truck wasn't strong enough to handle his workload. In 04 he purchased a 04 6.0 powerstroke and that only lasted about 7 years. After 2 EGR coolers, then deleted the EGR cooler and an engine oil cooler. Once the injector seats failed and put fuel in the coolant he parked that one too! In 2012 he went back to a Ram 5500
As far as pulling the powertrain and transplanting it. Unless you're putting it in another dodge that had a 5.9 you're back to cutting and welding mounts etc. Fummins are cool projects, the problem is, until you do some mods, a stock powerstroke makes more HP than that 12V. You're really only doing it for the "cool" factor.
Obviously the tires are shot. The fuel system would almost have to drained and flushed. As far as I'm concerned I dont think anybody factors in their own time when it comes to working on a personal project. Hell there's been a few nights just wasted leaning on projects shooting the **** and drinking beers lol.

 

[bradpac]

You have a chassis cab frame and rear axle. So even shortening the frame, you will still have to modify a pickup bed to fit if you're keeping it dually as the chassis cab axle is more narrow than the standard dually pickup. Also, the pickup frames have a kick up before the rear axles where the chassis cab frames are straight, not sure how a bed mounts to them.

What I'm getting it is it would be more work and money than just shortening the frame to put the pickup bed on it, especially if you want it to look right.

 

[3rdgendslmech]

You have a chassis cab frame and rear axle. So even shortening the frame, you will still have to modify a pickup bed to fit if you're keeping it dually as the chassis cab axle is more narrow than the standard dually pickup. Also, the pickup frames have a kick up before the rear axles where the chassis cab frames are straight, not sure how a bed mounts to them.

What I'm getting it is it would be more work and money than just shortening the frame to put the pickup bed on it, especially if you want it to look right.

I understand that. I haven't totally committed to it just yet. The whole reason behind turning it back into a pickup is I drive through 2 different tunnels or a bridge to and from work that transit authority police love to post up at. I've heard that they can't really say anything to you if it's for personal use and under 10,000 GVW. It wouldn't be a daily driver. Just a project truck to have around.

 

[38Chevy454]

How about shortening and then just build a simple 8 ft flatbed? Would that still cause concern about being a commercial truck? That would avoid the bed mounting hassles since as stated the frame is different.

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[bcschief]

If the frame rails are straight ladder style why not redrill the spring hanger locations and roll the axle forward to were ever you want it and bolt them in and cut off the rear of the frame were you need it ?

Brian

 

[66cj225]

What I want to know is if I were to shorten the frame, and put a 8 foot dually or regular bed, better part of my knowledge is to make "Z" cuts behind the cab where the frame is straightest correct? I'd fish plate the inside for extra strength but the truck most likely would not be worked hard.
I also heard some saying to avoid vertical welds???? Every fishplate I've seen and put on myself the verticals arent welded.
Personally I'd bolt the interior fish plates at the frame centerline with some half or three quarter bolts and nuts back on the original material for the safety chain effect. Even if the welds broke, it's still attached.

 

[matt_i]

Only thing I take issue with KPS motor sports pics is to clean to shiny silver base metal each side and not weld thru a bunch of "stuff". But the concept seems good. When the material is turning blue on the opposite clean side its usually a good sign that enough heat is being used.

 

[3rdgendslmech]

Sunday I'm going to take a little ride to the yard and take a good look at what I might be getting into. The one thing that sets this truck apart is that because it's a C&C truck it came with a "dummy" front axle, meaning its set up to take a 4x4 axle without having to change the suspension or steering components. It's just a straight axle. I already found a few NV5600 transmissions with transfer cases.

 

[Bogie1632]

Crazy thought...

Other than it still being a long truck, why not leave the frame alone, mount a bed, and build a box between the bed and the cab? Might have room for a tools, storage, compressor, welder...all sorts of stuff.

V/R
Bogie

 

[3rdgendslmech]

Crazy thought...

Other than it still being a long truck, why not leave the frame alone, mount a bed, and build a box between the bed and the cab? Might have room for a tools, storage, compressor, welder...all sorts of stuff.

V/R
Bogie

You know.....I thought about this also. Seen a few hot shot guys make a sleeper box then run 5th wheels, some of them mounted inside a regular bed or a flat bed also.
I do have a engine driven welder and a compressor so that'd be sweet to have to have those mounted and not take up pretty much all the bed space.

 

[bri_man57]

When you go look at it, take some pics and post them lol

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[kerrynzl]

Hey guys I've got a question, I'm not a welder by trade, but I like to think I do a pretty good job at it.
I haven't committed to the idea yet but throwing it out there to see who's done it before and hopefully get a little advice.
A friend of mine has a 95 Dodge 3500 with a 12 valve cummins and 5 spd manual. It's a regular cab with a 11 or 12' dump bed stake body. The only thing wrong with it other than its been sitting for about 15 years is the back of the cab cracked right above where the floor and cab meet.
What I want to know is if I were to shorten the frame, and put a 8 foot dually or regular bed, better part of my knowledge is to make "Z" cuts behind the cab where the frame is straightest correct? I'd fish plate the inside for extra strength but the truck most likely would not be worked hard.
I also heard some saying to avoid vertical welds???? Every fishplate I've seen and put on myself the verticals arent welded.
So that kinda throws the Z notch out the window? The only other ideal way to do this IMO is to slant cut the frame rails.

In our country we need to certify mods like that. And strict engineering rules apply.
If we don't want to pay a structural engineer, we have to do it by the book.
Our transport Nazis dictate a vertical join with a diamond fish plate.

I normally put the fishplate inside the C channel, get it signed off. Then I fold another smaller C channel that fits inside to box the frame.[to hide it]

I've also lengthened a frame with a Boxed C channel that overlaps the 2 joins [and added a section in between]

I am not saying the vertical weld is the best method, but our Land Transport Dept did do their homework for us.

 

[bigguns69]

https://www.google.com/search?q=fis...QGw&safe=active&ssui=on#imgrc=HQ2fMDKkjus_cM:

Truck frames usually use a higher grade steel compared to the sheet metal and bracket components. This is usually a more unique alloy with a higher carbon content which gives it higher yield and tensile strengths. Welding on higher carbon content steel, in the HAZ, (heat affected zone) area of the weld, can induce hydrogen embrittlement and initiate a crack in the weld joint or more likely right next to it. This is always possible to some degree.

You can minimize this by preheating the weld joint to about 500 degrees F with a torch before welding. You can also do things by not having a linear joint of the two mating ends, like a Z, scalloped, or angled **** joint to avoid the linear crack possibility. You can also add "Phish on top of the welded **** joint for added strength and a second point of failure protection. Some techniques will do this then also drill some holes and put bolts as another failure mode. This is often done on semi truck frame stretches.

I've included a link to some pictures as a guide. Most construction equipment put fish plate over straight line weld joints as shown in the pictures. That's what I would do. That's what I have done as over the years on farm and construction equipment.

 

[joe_padavano]

Truck frames usually use a higher grade steel compared to the sheet metal and bracket components.

Pickup trucks, not so much. GMC annually publishes an upfitters guide for aftermarket companies who build bodies for their trucks. That guide includes a chapter about lengthening and shortening frames. The GM frames (yeah, I realize we're talking about a Dodge) are mild steel. Heat treating is not an issue. The issues are 1) be sure to angle the welds to ensure there isn't a step function change in stiffness and 2) use runoff tabs at the edges of the flanges to prevent undercuts in the weld in those high stress locations.

 

[Brians VWss]

I like the 2 answers, of 1 relocating the rear axle to center the wheel of the new bed and cut off the rear overhang (only good if the rails are straight with no kick up). 2 centering the bed to the current configuration and mounting a box, welder or sleeper between the cab and bed. (Could potentially have a greater value then a regular truck )


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[Bighead38]

Didn’t shorten it but I replaced the end of the frame rails on this truck.

 

[bradpac]

I've heard that they can't really say anything to you if it's for personal use and under 10,000 GVW.

That truck should be 11,500 on the door sticker, not sure if that means a lot where you're at or if you can register it lower and be ok, but just another thing to think about.

 

[sberry]

I bevel to the outside. Then I weld the inside and then backgrind the bevel and weld the outside,,, then grind flush and smooth. Cant tell its been worked on.

 

[brownbagg]

you did a good job, I like it

 

[sberry]

Wire feed wire is pretty good especially on sections this thick. As I mention, inside out. A guy cant bevel up on the indide web but grinding on it can be done. I weld that first hot and fast then regrind the outside into the root smooth and weld the outside. Then grind the inside smooth then outside smooth. Homogenous, no bead left to edge crack. Mig wire has really good mechanical properties, almost s good as 7018. Maybe better considering rod condition. Can do it well stick too.

 

[Sportsman762]

If your looking to reduce the tolls in the tunnels by shortening the truck you might want to check on what the tolls are based off. In IL tollroad they have an passenger vehicle toll, however duallys must pay commercial toll. However the Chicago Skyway only charges off of axles.

Keeping the commercial vehicle inspectors off your truck would be reduced by the "not for hire" sign.

 

[JHenke]

A few rear frame pictures from a 1995 3500

 

[danielbuck]

I also heard some saying to avoid vertical welds???? Every fishplate I've seen and put on myself the verticals arent welded.

I've heard this as well. my take on it was that vertical welds are generally more difficult (for folks who don't weld for a living). So maybe that's the rationale for avoiding them. A good down hill weld might be better than a crappy uphill weld? I don't know.

I've done both up and down on frames and brackets on the frames, haven't seen any strength differences. But I generally over-build things stronger than the need to be, because I don't want to chance it.

I've also heard to round the fishplates.

Regardless though, whatever you do, I would plate it after you weld up the initial seam. When I've done this (to repair cracks in old frames) I've used a plate with 1 or 1.5" holes drilled in it, so that the weld is around the outside of the plate, as well as in two holes on the inside. I really have no real world basis for if this is better or not, but it seems like it would take a bit of stress off of the perimeter welds.

Take this for what it's worth, I'm just a hobbyist. But I've never had any of these repairs fail.

 

[3rdgendslmech]

Sorry guys didn't make it down there over the weekend. Had the kid's first birthday party over the weekend and spent Sunday recovering.
Today I reached out to a lady that does our light duty state inspections. She told me that as long as I'm not using the truck for commerce or to make money with I'm fine. I could pretty much buy whatever I wanted and would be okay.

 

[Capt Chrysler]

Cut it!

They stretched a bunch of them (Hot Shots) in the early 90's for sleepers.

If your worried, you can also run a boxing plate 3/8 in on the inside C of the frame.

Capt. Chrysler

 

[chaosracing]

Z cuts and fish plates are the best way to go about it. Also if you can back gas the weld. Meaning have 2 welders, but one not running wire, only used for the gas. As one person is welding on say the outside, have the other running the torch head along the hot zone of the weld with shielding gas. This minimizes the contaminates and reduces the amount of grinding needed on the inside before welding that.
Also as mentioned, bolting fish plates is a good idea. What I have seen other guys do is to weld and bolt them on. Used 7/16" or 1/2" grade 8 bolts and locking nuts.
You can also box the area where you make your cuts and welds. Boxing will help move the stress away from the welded areas.

Now another option that might be even better and surprised I did not see it......a frame swap.

 

[sweetk30]

did my 1987 k30 chevy frame chop down from crew cab to std cab and did a 45* cut and weld with my lincoln 140C 110 volt welder set up correctly . then did a diamond plate fish over it on the inside . no problems in 1.5 years now making it work like a 1ton 4x4 should . . . plowing snow / towing trailer / daily driver . . . no problems .

 

[bri_man57]

That truck is rad!

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[3rdgendslmech]

did my 1987 k30 chevy frame chop down from crew cab to std cab and did a 45* cut and weld with my lincoln 140C 110 volt welder set up correctly . then did a diamond plate fish over it on the inside . no problems in 1.5 years now making it work like a 1ton 4x4 should . . . plowing snow / towing trailer / daily driver . . . no problems .

This was gonna be my other option. This is how I've seen big rigs stretched out. They cut the drivers frame rail so that under a heavy load it wont try to pull itself apart. They also extend the fishplate 2 feet in each direction past the cut on the inside frame. So if it holds up for 80K+ lbs, then a 9K truck doing minimum work shouldn't be a problem.

BTW i'm a fan of the cut off red dump trailer....that's good thinking.

 

[sweetk30]

friend of mine use to be a heavy mechanic and he saw all kinds of cuts and wleds and plates done on truck and trailers . some different styles on same truck . as long as the weld was good he never saw them brake . he was doing fleet work so he saw the same trucks for years and years .

thats NOT a cut off dump truck . i will do a build thread with pics for ya . its just the bed on a custom frame and narrowed up axle . she was a simple fun build and worked great . was built for farm use only no road use .

 

[3rdgendslmech]

So here she is in all her glory. I was at his yard the other day looking at a bobcat I have to do some work on. The back of the cab is cracked above the mounts which was going on before it was parked. Pretty sure it was a combination of the weight he was hauling and the torque. The dash has one crack right down the center. Looking at it, it doesn't look like it'd be too hard to shorten the frame anywhere behind the cab and where the back half of the frame is riveted to the main frame. I forgot about it being a PTO dump. It'd kinda make loading a old farm tractor a lot easier specially if you mounted a winch

 

[sberry]

Z cuts and fish plates are the best way to go about it. Also if you can back gas the weld. Meaning have 2 welders, but one not running wire, only used for the gas. As one person is welding on say the outside, have the other running the torch head along the hot zone of the weld with shielding gas. This minimizes the contaminates and reduces the amount of grinding needed on the inside before welding that.
Also as mentioned, bolting fish plates is a good idea. What I have seen other guys do is to weld and bolt them on. Used 7/16" or 1/2" grade 8 bolts and locking nuts.
You can also box the area where you make your cuts and welds. Boxing will help move the stress away from the welded areas.

Now another option that might be even better and surprised I did not see it......a frame swap.

I mention this in another post. You can grind flush on the inside but back grinding a groove can't be done on the inside of the C. We simply leave a little gap on a pickup frame, weld it from Inside first, this alows easy back grind in the groove. Weld it from the outside. Grind flush.

 

[teal95]

I believe Chrysler was working on offering a "Long Haul" package on the 3500 chassis cab diesels that made up the extra length (standard chassis cab has the correct length for.a 9' bed) with. 100 falling fuel tank.