Want to build a Gen1 DodgeCummins for towing, up to 35000 lb GVWR, what engine should I build?

[The Tow Rat]

Hey all,

I have a 1991 Cummins 5.9 2500, which I would like to build up as a 35,000 lb GCWR tow mutant.

I will be doing a bed delete, Spicer S-111 or some similar rear axle, frame mounted gooseneck, and BIG HONKIN' DISK BRAKES at all 4 corners. I really want a 6 speed manual, but I'm not sure what transmission to use for over 900 lbs ft. of torque. Will dive down that rabbit hole in a future post.

Regarding the 5.9, which is my topic for this post, the first step (of course) will be to ditch the VE pump and get a a P-Pump. Beyond that, all will be fairly standard 12V performance hop-up which I will not bore you with right now.

Here are my questions for this post.

1) I think I know the answer to this already, but I would like to hear what others have to say about it: 12V vs 24V.

2) I think I know the answer to this too, but... 5.9 short block vs 6.7 short block. What do people think?

Regards,
The Tow Rat

 

[Dean2]

If you are going to tow 35,000 lbs, build yourself a Peterbuilt. Nothing about a 91 2500 was designed for that weight, from frame, to springs, to brakes, transmission and everything else. That pickup is far too light to handle that weight at highway speeds.

 

[392DevilDog]

Thr engine is the least of your worries as mentioned....

 

[The Tow Rat]

Yes, Dean2 and 392DevilDog, you are both absolutely right; the engine is actually the easy part!
But as to whether a Pete is needed... no, I don't really think so. Take a look at the '21-'24 Ram 3500HD. That is what gave me the idea. Ram touts a rather stunning -41600- lb GCWR for the new 3500HD trucks!

Admittedly there's a lot I would need to do to my Gen1 2500, to emulate a '21-'24 Ram 3500HD. But hey, have you looked at list prices for a new 3500HD? I got my Gen1 5.9 for $3200. A new 3500HD starts at $48,735 and that doesn't include the Max Tow Package. The difference is more than $45,000. For that, I can buy a lot of nice heavy duty parts!

I'm not worried about the rear axle, or the springs, or the brakes. I can find dually class 5 sized rear axles with 10,000 lb and up GAWR and nice big disk brakes with vented rotors, from a couple different possible sources.

Some things that are going to need sorting out, are the transmission and the frame. For transmission I'm initially thinking Fuller FSBO9406A six speed. But I don't know how much it weighs, and I don't know if it will fit.

Regarding the frame, yeah you are right, that is going to be a challenge. The new 3500HDs box in a big section of the frame in the back. I could do the same thing. But I think I am leaning towards using the existing frame unmodified (avoids welding on it, which is good because its heat treat won't be compromised) and adding a bolt-on DOM tube frame for reinforcement. Since I am comitted to a bed delete, there will be plenty of room to add something like that.

I haven't thought about the front axle much yet. A newish beam axle out of a class 5 truck, again with disk brakes sized for that application, would be the obvious first go-to. But I'm not sure how I would go about adapting the springs and steering. It might have been easier if my truck had a 4x4 front end on it.

Hmmm... Maybe I need to get a 4x4 frame and do a frame swap, so that the front suspension will be closer to what I would need to adapt a heavy duty beam axle?

Regards,
The Tow Rat

 

[Gr8bawana]

Yes, Dean2 and 392DevilDog, you are both absolutely right; the engine is actually the easy part!
But as to whether a Pete is needed... no, I don't really think so. Take a look at the '21-'24 Ram 3500HD. That is what gave me the idea. Ram touts a rather stunning -41600- lb GCWR for the new 3500HD trucks!

Admittedly there's a lot I would need to do to my Gen1 2500, to emulate a '21-'24 Ram 3500HD. But hey, have you looked at list prices for a new 3500HD? I got my Gen1 5.9 for $3200. A new 3500HD starts at $48,735 and that doesn't include the Max Tow Package. The difference is more than $45,000. For that, I can buy a lot of nice heavy duty parts!

I'm not worried about the rear axle, or the springs, or the brakes. I can find dually class 5 sized rear axles with 10,000 lb and up GAWR and nice big disk brakes with vented rotors, from a couple different possible sources.

Some things that are going to need sorting out, are the transmission and the frame. For transmission I'm initially thinking Fuller FSBO9406A six speed. But I don't know how much it weighs, and I don't know if it will fit.

Regarding the frame, yeah you are right, that is going to be a challenge. The new 3500HDs box in a big section of the frame in the back. I could do the same thing. But I think I am leaning towards using the existing frame unmodified (avoids welding on it, which is good because its heat treat won't be compromised) and adding a bolt-on DOM tube frame for reinforcement. Since I am comitted to a bed delete, there will be plenty of room to add something like that.

I haven't thought about the front axle much yet. A newish beam axle out of a class 5 truck, again with disk brakes sized for that application, would be the obvious first go-to. But I'm not sure how I would go about adapting the springs and steering. It might have been easier if my truck had a 4x4 front end on it.

Hmmm... Maybe I need to get a 4x4 frame and do a frame swap, so that the front suspension will be closer to what I would need to adapt a heavy duty beam axle?

Regards,
The Tow Rat

Someone who supposedly has this much knowledge on this stuff wouldn't be here asking for others opinions.

 

[Dean2]

Someone who supposedly has this much knowledge on this stuff wouldn't be here asking for others opinions.

View attachment 530844

Started to think exactly that, it is why I quit responding. On top of that, if he is serious there is clearly no way to talk sense to him, he already knows it all.

 

[The Tow Rat]

Troll? Don't know where that is that coming from... Guys this is only my 4th post on the forum, or something?

Wow, is someone just allowed to ask honest questions here?

Anyway give me a break, I'm a long time Cummins Ram owner and I have been towing with stock trucks for decades, but this is the first time I've contemplated modifying one of my trucks specifically for towing heavy. So I am bound to ask stupid questions... Par for the course.

 

[rzr6-4]

With enough time/money/effort anything is possible, but with your list of parts swaps including pretty much the entire thing, sound to me like you are essentially buying a whole new truck and just doing a cab swap on it with the one you have already, as that is pretty much the only thing not on your list.

Therefore.... just buy a 4500/5500 and just do a cab swap to make it look like your gen1.

 

[The Tow Rat]

Anyway I'm in kind of in a hurry to figure out how to build a Cummins powered truck for $15k-$20k-ish that can pull a long 6% grade at 55 at 35000 lb GCW. And to do all that without hitting crazy EGTs or killing the transmission.

Thanks again @Dean2 and @392DevilDog, for pointing out that modding a Gen1 is probably going down the wrong rabbit hole. Part of my motivation was avoiding electronics and smog, plus I was just thinking to start with what I already have, but I agree that plan doesn't really make sense.

So now I have my eye on a '04-1/2 Cummins 3500 dually with NV5600, tow package, and 12200 GVW rating.

I talked to Cody Albrecht at Superstick Transmissions. He says he can build me an NV5600 that can handle 1000 hp so I think that takes care of the transmission.

Now my questions is, 5.9 24V vs 5.9 12V. Forget the tumble swirl discussion... what I really need to know is which will work better for my application.

Obviously, if I was going to keep it registered in Ca, 5.9 24V would be the only answer because of smog, but I'm thinking as a backup I could maybe get it registered through a family member in a non-smog area in Wa State.

I want to build the engine with a really flat torque curve limited at less than 800 lbs-ft, and putting out 450-ish hp at 3000-3200 RPM, to take it easy on the transmission.

My question:
Which platform is better to build a 450-ish hp 5.9 with less than 800 lb-ft of torque, 12V or 24V?

Gr8bawana,​

Character attacks for their own sake usually don't accomplish much in forums.

Regards, and thanks again,
The Tow Rat

 

[Scottly]

I haven't heard anyone mention frame issues, but I'd have to think that needs to be a consideration. It's your money.

 

[The Tow Rat]

With enough time/money/effort anything is possible, but with your list of parts swaps including pretty much the entire thing, sound to me like you are essentially buying a whole new truck and just doing a cab swap on it with the one you have already, as that is pretty much the only thing not on your list.

Therefore.... just buy a 4500/5500 and just do a cab swap to make it look like your gen1.

rzr6-4,​

Yeah I looked at 4500s and 5500s. I even looked at (Sheesh) Fords. Nothing I looked at has the combination I want... Cummins b series, 6 speed with reasonable ratios, under 7000 lbs vehicle weight, 35000+ GCWR, and under $20k.

All of the 4500s and 5500s I looked at are optimized for GVWR not GCWR. For example, if you look at the new Ram 4500s and 5500s compared to the new 3500HD Dually with the max tow package, the GCWR of the 4's and 5's is LESS than the 3500HD Dually with the max tow package!

Yeah, I get that the 4's and 5's include pro hotshots in part of their target market so their GCWRs are probably more conservative, but still!

Regards,
The Tow Rat

 

[The Tow Rat]

I haven't heard anyone mention frame issues, but I'd have to think that needs to be a consideration. It's your money.

Scottly,​

Regarding frame issues, you mean with respect to limiting torque?

No, I was thinking limiting torque to take it easy on the transmission. At least that's the way I see it. Any counterarguments, flame away.

Nomex On.

Regards,
The Tow Rat

 

[The Tow Rat]

Or did you mean frame issues on a Gen1? Sorry not sure what you mean...

 

[chri5k]

Anyway I'm in kind of in a hurry to figure out how to build a Cummins powered truck for $15k-$20k-ish that can pull a long 6% grade at 55 at 35000 lb GCW. And to do all that without hitting crazy EGTs or killing the transmission.

Thanks again @Dean2 and @392DevilDog, for pointing out that modding a Gen1 is probably going down the wrong rabbit hole. Part of my motivation was avoiding electronics and smog, plus I was just thinking to start with what I already have, but I agree that plan doesn't really make sense.

So now I have my eye on a '04-1/2 Cummins 3500 dually with NV5600, tow package, and 12200 GVW rating.

I talked to Cody Albrecht at Superstick Transmissions. He says he can build me an NV5600 that can handle 1000 hp so I think that takes care of the transmission.

Now my questions is, 5.9 24V vs 5.9 12V. Forget the tumble swirl discussion... what I really need to know is which will work better for my application.

Obviously, if I was going to keep it registered in Ca, 5.9 24V would be the only answer because of smog, but I'm thinking as a backup I could maybe get it registered through a family member in a non-smog area in Wa State.

I want to build the engine with a really flat torque curve limited at less than 800 lbs-ft, and putting out 450-ish hp at 3000-3200 RPM, to take it easy on the transmission.

My question:
Which platform is better to build a 450-ish hp 5.9 with less than 800 lb-ft of torque, 12V or 24V?

Gr8bawana,​

Character attacks for their own sake usually don't accomplish much in forums.

Regards, and thanks again,
The Tow Rat

I am a bit confused, is that $15k - $20k not including the base truck? Otherwise, I don't see how to buy a truck, build an engine and transmission for that amount of money. Not including any suspension or other upgrades required to get to 35,000 GCW. One would think if it could be done, hotshots all over would be doing it.

 

[Scottly]

Scottly,​

Regarding frame issues, you mean with respect to limiting torque?

Yes. Seems that might be a factor

 

[The Tow Rat]

chri5k,​

The Gen3 truck I found is a good deal.

I think the engine objective can be met just with exhaust, intake, and tuning. Does anyone know of an open source tuning interface?

Oh yeah and can I get sufficient EGT reduction using just H2O or Methanol injection? Or will I to need a bigger intercooler, or a bigger turbo to keep EGTs under control?

I think the NV5600 build is going to be in the range of $2000-$2500; depends on what parts need to be replaced.

I believe I can get away with leaving the front suspension unmodified. The hitch location (front/rear) will be set to carry most of the gooseneck weight on the rear axle. Also with a bed delete, I will get the hitch down as low on the frame as possible to minimize braking load transfer.

The rear axle will likely be swapped out for a Dana S110 or S130 series, or maybe a Meritor MS-13X series. I am told that these things can be had for less than $1000 used. I'll need to look for one that comes with the springs.

And I'll need to get a new welder, that can do a good job on both TIG and MIG. But that I consider a capital cost, not part of the truck.

Finally I would eventually part out a significant chunk of the donor truck. The bed, the entire cab, etc. Hard to say how much this will bring. But just as an example, used doors are $400 each and there are four of them. I figure $3-4000 if I am patient enough to sell 50% of the parts.

The harness will be the biggest challenge of this build. It will take a long time to figure out, but it won't cost much because I will have two harnesses to work from for parts.

Regards,
The Tow Rat

 

[The Tow Rat]

Oh yeah and for hotshots, their reputation depends on them being on time every time, so having a dead reliable truck is mandatory. They surely can't rely on used parts.

Plus for them, time is money. And a project like this takes a lot of time. I'm retired.

Regards,
The Tow Rat

 

[Gr8bawana]

Troll? Don't know where that is that coming from... Guys this is only my 4th post on the forum, or something?

Wow, is someone just allowed to ask honest questions here?

Anyway give me a break, I'm a long time Cummins Ram owner and I have been towing with stock trucks for decades, but this is the first time I've contemplated modifying one of my trucks specifically for towing heavy. So I am bound to ask stupid questions... Par for the course.

If you were really a long time Cummins owner and have so much knowledge you would not be asking for opinions. Just do it and tell us how it went.
Heck will freeze over before that happens.

 

[JayLeonard]

If it were me I’d use a 5.9 with a Bosch P pump. FWIW the early non inter cooled 91 D250 I had was an oddball. It had a 1 1/4 ton rear axle. Probably could have handled what you’re planning but the Getrag 5 speed would have Grenaded.
Good luck on your build.

 

[ppine]

6.7 liter Ram diesel, 4.11 rear end and an Allison trans with 2 gear ranges.