The overly complicated disaster that is this swap project

[KansasIDI]

Back in late February of 2025, I bought a 1994 Ford F350, regular cab 11’ bed 4WD chassis cab dually truck, with a 7.3 IDI and E4OD automatic. Real straight body on the truck. Bought it off Purplewave.

There was a video on the listing of the truck cranking over, was claimed to be non running, but had an even crank.

When I went to pick it up, me and my posse had it running within 15 minutes. Unfortunately, the E4OD had a bad front seal.

So I hauled it home, and began rebuilding a different E4OD that I had laying around.

However, once I had finished that, I made another foolish Purplewave purchase, in July of ‘25. A 5 speed Allison 1000 series, remanufactured, designed for a 2WD 2001 Duramax. It was being sold as an inventory clearance sale, some shop was closing up in Kansas City.

After that, I got ahold of CAconversions in regards of a kit to put that Allison behind an IDI. They wanted $7k for a swap kit, and another $2k to put a 4WD tail housing and output shaft on that transmission, which can be done without full disassembly. I did not order one. I will probably sell that Allison.

During this time, I had been accumulating performance parts for this truck, turbo kit, fuel system, head studs, etc.

However, I wound up putting most of that stuff onto my 91 F-Superduty, which I recently blew the engine in. No, it wasn’t studded. But the IDI that will be going back into that truck will be.

At any rate, also during this time, I had contemplated moving the F350 cab onto an F-Superduty chassis that I had laying around, and looked into 4WD options for that. I later thought of just leaving it 2WD, and using the Allison behind an IDI, but I would have to get more performance parts.


However…
I bought something else off Purplewave just today. A 2008 Freightliner MT45 stripped chassis with a step van body on it, equipped with a 6.7 Cummins and 6 speed Allison 1000 series. The electronics are largely compartmentalized onto and around the powertrain, and seems to be made as compact as possible.

So now, my crazy idea is to swap that engine and transmission onto the F-Superduty frame, and drop the F350 cab over that.


TLDR: 6.7 Cummins and Allison 1000 series swap into Ford F-Superduty

Now I need to get over to St Louis and drive the Cummins donor back to Kansas…

 

[Old_F250_IDI]

Looks like you are a busy man...

 

[KansasIDI]

Looks like you are a busy man...

I guess.

I’m sure all this will take awhile, but I’m motivated to work on this project, if I could just decide what I’m doing… the Cummins and Allison combo intrigues me, I’d definitely like to try and make it work.

 

[lotzagoodstuff]

First and foremost: As long as you are buying all that stuff pretty right, I see no issues. You can and will sell all that stuff as soon as you decide what to keep and what to offload.

6.7 Cummins and Allison 6 speed is pretty interesting, especially in the Freightshaker chassis as they are less "integrated" in that chassis than they are in the high volume pickups. I see and agree with your thinking, with one caveat: I can't say I'm a giant fan of any of the older Allison's from an efficiency/mileage standpoint. Maybe it's because I see lots of the 3000/4000/4500 stuff in the class 8 space, but in my opinion they are all HP eaters. Super durable and great in vocational applications, but if I'm going through the complexity of a transmission swap, I want lots of gears and efficiency for freeway driving. But you have the powertrain, it's all together, functional, paid for, etc and it would be a giant upgrade compared to anything that era of Superduty came with. I say do it.

But since you are already hoarding stuff and have overbought components already, I'm going to send you down one more rabbit hole: call these guys and see if they are interested in adding a 10 speed IDI swap to their offering. Any newer 5 and 6 speed auto is better than the E4ODs we all live with in these trucks, but the latest 10 speed autos are just flat out awesome.

In the mean time: continue to PurpleWave it up!

Home - Powertrain Swap Solutions

www.powertrainswapsolutions.com

 

[KansasIDI]

First and foremost: As long as you are buying all that stuff pretty right, I see no issues. You can and will sell all that stuff as soon as you decide what to keep and what to offload.

Yes.

6.7 Cummins and Allison 6 speed is pretty interesting, especially in the Freightshaker chassis as they are less "integrated" in that chassis than they are in the high volume pickups.

Indeed.

I see and agree with your thinking, with one caveat: I can't say I'm a giant fan of any of the older Allison's from an efficiency/mileage standpoint. Maybe it's because I see lots of the 3000/4000/4500 stuff in the class 8 space, but in my opinion they are all HP eaters. Super durable and great in vocational applications, but if I'm going through the complexity of a transmission swap, I want lots of gears and efficiency for freeway driving.

I understand and largely agree. May I note, in this application, that Allison is also a 1000 series, but a 6 speed, double overdrive variant. 0.711 fifth and 0.614 sixth. However, I may note that efficiency isn’t necessarily the goal with this build. A factor, certainly.

But you have the powertrain, it's all together, functional, paid for, etc and it would be a giant upgrade compared to anything that era of Superduty came with. I say do it.

That was my thinking as well. Plus, that Freightliner was a very good deal IMO.

But since you are already hoarding stuff and have overbought components already, I'm going to send you down one more rabbit hole: call these guys and see if they are interested in adding a 10 speed IDI swap to their offering. Any newer 5 and 6 speed auto is better than the E4ODs we all live with in these trucks, but the latest 10 speed autos are just flat out awesome.

That’s an interesting idea. I’d call and ask if such a thing is possible, but I’ll probably stick with the 6 speed Allison, as it’s already configured to work with that 6.7 Cummins.

 

[KansasIDI]

By the way, the 6.7 Cummins in a Freightliner application, at least any that I have seen, is a rear gear train engine. The timing case isn’t particularly large, but it is worth noting.

I also haven’t decided how to mount the powertrain, part of me would like to remove the engine cradle and build large crossmembers at the front and rear of the engine, like a medium duty would have. I would have lots of computer drawing and math to do in order to make it the right combination of strong and flexible. Leaving the engine cradle may be simpler, but for space constraints, it also might not be. I think I could build medium duty style mounts, and leave or slightly modify the engine cradle. But removing it might also be an option. For the now, I will count on leaving it as it is, and determine my mounting solution on mockup.

Oh and, I don’t think the engine will remain California approved…

 

[Black dawg]

Would be nice if it was front gear train. Pretty neat stuff though.

 

[KansasIDI]

Today is the day

I shall go and get the donor vehicle

It will be raining for a large portion of the trip

 

[KansasIDI]

Got it home. Had to get some mirrors for it, the ones on it were so wobbly that you couldn’t see behind you, not ideal for a 6 hour interstate trip. Then it ran fine the whole way back.

The engine has a little bit of injector haze when started cold, so those will need replaced. I was aware of that going into this, it seems to have been reflected in the very low price I paid for it.

Clears up and runs good after 2 minutes of being cold started. Had no trouble with it, besides the mirrors.

On the return trip, my Dodge had what I think was a fuel pump failure, near Lawrence KS. Now I have to go back and get it tomorrow, but that’s not so far away.



@Jesus Freak

My respects to you for driving a step van all day every day when you worked for UPS and FedEx… also I see why a Cummins isn’t exactly pleasant in that application. Very noisy…

 

[Jesus Freak]

Got it home. Had to get some mirrors for it, the ones on it were so wobbly that you couldn’t see behind you, not ideal for a 6 hour interstate trip. Then it ran fine the whole way back.

The engine has a little bit of injector haze when started cold, so those will need replaced. I was aware of that going into this, it seems to have been reflected in the very low price I paid for it.

Clears up and runs good after 2 minutes of being cold started. Had no trouble with it, besides the mirrors.

On the return trip, my Dodge had what I think was a fuel pump failure, near Lawrence KS. Now I have to go back and get it tomorrow, but that’s not so far away.



@Jesus Freak

My respects to you for driving a step van all day every day when you worked for UPS and FedEx… also I see why a Cummins isn’t exactly pleasant in that application. Very noisy…

Yeah, the contractor i worked for had a couple trucks with Cummins and it is crazy loud sitting on top of one of those.....in an aluminum box....you can keep it.