93 C3500 to K3500 Complete Restoration / Duramax Swap

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JScott23

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The thread says it all.....

For those who don't know me or the truck, I am jumping back on the forum after many years away. Due to the evolution of Facebook groups, I had taken about 5-7 years off from the forums. I finished the original restoration" of this truck from the thread below.


The truck was my childhood truck growing up, and a few years ago I gave it a quick refresh. It was my first attempt at paint, and I swapped in a 12 valve Cummins & 47 RE on the original 93 C3500 2WD chassis. At the time, I thought the 12 valves simplicity and longevity would be a perfect drivetrain in a truck I otherwise expect to keep forever.

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Obviously, it wasn't good enough for what I want of that truck. This is my "Flagship" rig and one I truly never see myself parting with. Through this "Refresh" I was somewhat reserved to fully dive in and really give the truck the complete overhaul it deserved. (I Kept the original Midwest doors, textured the rockers, used POR15 on the frame, kept the 2wd chassis, and really just did more of a refresh rather than a restoration)

Ultimately 2 years after completing the project I just couldn't live with it as had been done....

So before you all ask....
"why in the world would you rip that truck apart???"


First off, I always wanted to 4x4 swap it. The K series trucks just have a better stance to them. And as much as I wanted to keep it original, i just have a taste for the 4x4 trucks. The 90's 4x4 sticker and flares just look better. I also felt like I would have always have to keep another 4x4 around if this truck remained 2wd. Even though this truck will never see snow or Midwest winters again. Not anytime soon, but eventually i'll trim the fleet down to just one GMT400. And when that time comes, I want this truck to be capable of being a do-it-all rig.

Now, in my opinion, the truck looked great, but my painting skills have grown significantly since starting on this project, and I made some rookie mistakes that only experience could mend. I've since become a better painter, and therefore I knew that couldn't live with and would need to redo at some stage.

As for the powertrain, doing the cab on restoration and keeping the rusty 2WD frame plastered in POR-15 was a mistake. the 12 valve Cummins is widely regarded as the king of the Diesel World, I wasn't impressed in this particular application. This truck does tow, but it's mostly a cruiser. The Cummins was just very loud and obnoxious to say the least. Additionally, the Cummins has a very low power band and doesn't make for a great driver in my opinion. Tons of low-end power but lacks a the RPM range and horsepower to really make for a comfortable driver in my opinion. I also could not get over the noise factor.





So, in March of 2021 apart it came...

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No turning back now.....
 
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JScott23

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At this point, I wasn't 100% sure where I would land on this whole adventure.

I knew I wanted to go 4x4, on a K series frame. The IFS is simple and keeps a factory look. I wanted to go back to factory trim, on factory steel wheels with some 265/285 m/t tires. I honestly had no real direction on powertrain. I really was leaning towards going back to the original mechanical 6.5. I knew I wanted to do a sandblasted chassis, with everything new.


With more experience under my belt and a dream in mind, I started on the hunt for a 4x4 frame. Car-Part.com led me to Premier Auto Rebuilders in Phillipsburg Missouri where I wind up with this 96 K3500 SRW chassis. Pretty clean for what was available within a reasonable distance of me here in Illinois. They were great to work with, and promptly responded to my numerous requests for pictures.

After an 11 hour round trip, here she was.

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Met a local sandblaster through my brother-in-law, and they blasted the frame for me.

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Hit the paint with some Carboline Carbothane 8854 which is a industrial salt and chemical resistant polyurethane which should keep this thing looking minty for a while.
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Then we fired up the parts cannon.

Timken Hubs
AC Delco Steering Parts
AC Delco Joints
New Sway Bar
Wagner Rotors
98+ Forged Lower Control Arms
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I also bought brand new leaf springs from ATS Spring. Hit those with carboline paint as well. Haven't bought shocks yet but plan to use bilsteens.

For the tie rods, i actually purchased the Cunningham Machine tie rod sleeves, and plan on upgrading to the Mevotech TTX rod ends. I know Kryptonite makes front end parts for these trucks, but it's just not necessary. I wont be doing any sled pulling or boosted launches with this thing.

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A huge step in this project was going to be getting the rolling chassis done. That helped in not having a bunch of dead weight clogging up space. I built a cab dolly for the cab, and made a cheaper one for the bed.
 

JScott23

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As for the body,


I mentioned above I was somewhat hesitant to tear into this thing. I was afraid to disturb the interior which is kind of the heart and soul of the build in my eyes. However, once rust sets in, there is only one way to fix it. Replacement of any panel with it.

And thus, I stripped the cab completely.

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And even though i planned on ditching the noisy Cummins, i threw some Kilmat down. Now i decided not to pull the headliner and interior trim. It just didn't need to occur. I did strip all the seals this time making for a better paint job.

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I cut out the rockers and welded new sheet metal in.

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Added some miscolored, but brand new southern sheet metal. My wife and I actually used a parts run for an excuse for an overnight trip to Nashville TN for a few of these doors.

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Now for the bed...

I have a desire to make this truck appear as if it was a mint barn find. And for that reason, I wanted a painted bed with no bedliner. And so, I once again called on my sandblaster to just save me a ton of elbow grease.

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This bed is actually a rust free spare i had. It's probably the nicest piece I own so it gets the call for this project.

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And just like the underside of the cab, i hit the underneath of the bed with a coat of epoxy primer and raptor liner. An undercoating that should last for a long time.

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So while the bed was pretty much set for paint, I jumped back to the chassis. Hopped online and lit up the stainless catalog from Linestogo.com.

Stainless Brake Lines
Stainless Fuel Lines
Stainless Transmission Cooler Lines

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And while I was on that stainless kick, I ordered Jamo's 4" Stainless Exhaust. I plan to add a MBRP Muffler in the future.

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Found an absolute mint core support and added a curt gooseneck hitch bracket. I'm not sure i'm going to add the gooseneck hitch, but it's there if I ever decide to.
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I was cruising right along.... until February 2022 rolled around. A good buddy of mine connected me to a sale of a 2001 LB7.

I had often flirted with the idea of a Duramax, and had kind of gone back and forth over the 6-10 month period i had started this project. I was always intimidated by their complexity over some of the other diesel engines I was familiar with. Ultimately, i'll always be a 6.5 guy, but their market and support seems to be dying. I've also seen quite a few friends put big money into 6.5 rebuilds only to have issues with block decks and other odd failures. The Duramax is a more powerful and a longer lasting motor. It's also just as quiet if not quieter than the 6.5 is.

This decision was actually made on much less of a whim than it might appear. Since i took the truck apart, i've relentlessly evaluated the powertrain for this truck. It almost drove me a little crazy to some extent. Going back and forth between simplicity, cost, reliability, longevity, and assessment of the purpose/meaning behind the project.


And so here we have it.

01 LB7 Duramax.

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Obviously, I decided to take the risk, and drove to Kansas City, MO to pick it up. Great seller, as I was able to get running videos, and buying from a friend of a friend made me feel warm about the idea of buying a used engine. About a 12 hour round trip. There is more to that story, but that's a story for another time. (lesson, don't take 370k trucks on road trips)
 
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JScott23

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Now i'm going to go a slightly different direction than most folks on this swap, for a variety of reasons.


I'll be using a 4L80E and a slip yoke BW4401 from a 93 K3500 RCLB.


1. They're both here and readily available for rebuilds. The transfer case also matches my 94 K3500 single cab and i have a desire to make both of my trucks pretty much identical from a parts perspective so i don't have to keep track of what's what between the two trucks.

2. My truck is a 93, so it has the mechanical rod style shift linkage. For that reason, it's easier to keep the 4L80E rather than rigging up linkage. I can also retain OEM drivelines and a OEM transfer case going this route. It'll also allow me to convert to this engine without having to do a body lift or modify the transmission tunnel.

3. This truck will essentially be a Sunday cruiser. I don't intend to hop up the motor, and just want it to be a recreational driver / occasional tow rig. The 4L80E is highly underrated IMO and can be built to hold power. I intend to use Jakes Performance in TX to do the 4L80E rebuild.

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I'll get into some of the conversion details in a later post, however I've already spoken to a few people who are heavily vested in the 4L80E platform and with some billet goodies, this transmission will hold up just fine. I also drive like an adult, and haven't smoked many transmissions in my years of driving.
 

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PURPOSE OF THIS THREAD:

My main reason for putting this thread together, is to document this build in a more comprehensive manner than i'm able to do on social media. Through all of my research i wasn't able to find a really good write up on this swap. Hugh Jeffries from CT would be the exception. He's done a great job on Youtube.

Personally, i'm not really interested in doing a vlog on this. But after chatting with another buddy of mine, i agree there needs to be a reliable source of information on this conversion. I continue to get contacted regarding how useful my write up was on the Cummins swap. And i'd be happy if this can help guide someone through a swap. It'll also be a place where i can refer folks who have questions.

For those who want to follow some of my past builds that might not be documented on here, check out my instagram. (J7Scott23) You'll probably see more real time updates on there, but i'm going to try to be diligent about keeping this thread updated.

Obviously, there is more than one way to skin a cat, and i'm surely not the first to do this swap. I'm also probably taking a route that a majority of people would rather not go in retaining the 4L80E. However, i feel there are several other variables about this swap that aren't documented elsewhere. And I have a high attention to detail and will not settle for anything less than a factory appearing swap. And for that reason, I hope this thread is valuable.
 

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One of the first steps of any swap.... Dropping the motor in.

With this particular motor, its clean. It ran great. Now although this truck is a complete restoration, the motor doesn't need to be completely rebuilt. I do want this thing done at some point this decade... Everything I intend to do to this thing i can do with the motor in the chassis. I intend on doing injectors, a new water pump, and some front/rear seals, along with some other various things but overall, it can go in now. It also helps to clear up my shop floor. The transmission and transfer case will be rebuilt, but for now they're in the chassis for mockup.

Before i paint anything i want this truck to be pretty much fully operational so i'm not making any last minute changes on a freshly painted firewall.


MOTOR MOUNTS:
For motor mounts, the diesel page is about your only option. I was very impressed with them, and at right around $200 they're a good value. They retain the factory clamshell mount. I didn't feel the upgrade to poly was necessary. They're a well made product and their installation is straight forward.

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I proceeded to drop the engine in the chassis and noticed right away there was going to be an issue. The lower differential mount hits the bottom of the oil pan. I immediately reached out to some others who had completed this swap. I found that the hammer was the typically the remedy for this clearance issue. I didn't want to risk distorting the oil pan, and thus sought an alternative to the hammering method.

I ordered a rather expensive PPE cast aluminum oil pan. A few hours after taking it out of the box, I took the grinder to it to solve the clearance issue.

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Luckily i was connected to a great local fab guy who was able to notch it.

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Some ceramic engine paint and it looks like it was meant to be. In this picture you can see the clearance issue. (Truck has no differential in it yet)

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JScott23

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Overall, i'm very happy with the fitment.

Much better than the Cummins. These chassis were designed for a V8, and this motor sits in the chassis nicely. The 4L80E bolts right up and will allow me to retain my shift linkage. The transmission lines with a little love fit nicely. I love the Duramax battery cables which just keep a clean routing of the power & ground cables.

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Now the 4L80E sits a little lower than the Allison would. With a 3/4"-1" spacer at the bottom of the transmission mount, the motor sits at the same pitch as a factory 6.5 fits in the same chassis. Which will keep all drivelines at the same angle.

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