72 GMC Longbed Duramax Swap
 

Hey all!

This weekend started the beginnings of a project.
But first! I want to brag!

This truck was bought brand-new in 1972 in Southern Indiana, by a family living in New Salisbury, IN. Unfortunately, the husband of the family died in '74. After that, the truck was parked in a barn, and used very sparingly to haul trash.

My dad bought it in 2002, with 39,6xx miles on it, and parked it in HIS barn. He had always wanted a truck like his "first car."
But, he wanted a shortbed, and he just couldn't bring himself to cut on such a great specimen of a truck. So, it sat in HIS barn for 10 more years.

In 2012 I deployed to Afghanistan, with the Army National Guard, and when I returned home I started looking for a 67-72 truck like MY first truck. After spending 2 weekends checking out craigslist finds, and finding them lacking, or needing much much more work than either of us were interested in doing, Dad offered to sell me "ol' blue" for the same price he bought it. I of course accepted.

I got married in 2013, and used the truck to move, and for trash, and it now has 41,xxx miles on it. A friend of mine owns a junk yard, and told me about wrecked duramax that he had just bought, T-boned, totaled, but the engine is in perfect shape.

So, here we go!!!

Re: 72 GMC Longbed Duramax Swap
 

You'll have to excuse the Horrid Quality pictures, my phone is a tad scratched up. However, next weekend when we work, i'm taking my actual camera.

Dude in the ball cap is my dad, holding my nephew.
The guy in the black shirt is one of our best friends that realistically is going to be doing most of the work while i hold the flashlight. That dude is Charlie Daniels of the torque wrench.

Re: 72 GMC Longbed Duramax Swap
 

One weekend down!

next weekend the aim is to get the duramax on the frame. I bought these http://www.ebay.com/itm/like/2314549...lpid=82&chn=ps motor mounts, does anyone have any experience with them? I'm planning on buying some tough Polyurethane mounts to pair with them.

I'm also starting to research what i'm going to need to do for wiring this bad boy. I've done some reading around here on the subject, and i have a little experience. I painless'ed my first truck, which is no GREAT feat, but it taught me quite a bit.

Re: 72 GMC Longbed Duramax Swap
 

Subscribed and good luck with your build. I used the same mount adapters that you have posted. I went from the adapters to a small block prothane mount to factory small block engine stands on the frame. I had to space the stands up 1.5" on the frame rail and 1" on the crossmember for pan clearance. I guess you know you have to raise the trans tunnel to get the Allison to fit. The forklift will sure make it a easier. I think dmax/allison is around 1100 lbs and is a little sketchy with a cherry picker.

Re: 72 GMC Longbed Duramax Swap
 

Nathen - Welcome to the site and allowing us to follow along. I will be watching this one. :metal: :metal:

Re: 72 GMC Longbed Duramax Swap
 

Subscribing because this is awesome

Re: 72 GMC Longbed Duramax Swap
 

Nathan, welcome to the site, and thanks for your service! Nice truck, and I like the direction you're going with it! Keep the progress pics coming!

Re: 72 GMC Longbed Duramax Swap
 

aww gee wiz guys! thanks!!

Joel.e Thanks so much for telling me that, i have the mounts that you described ready to go this weekend! i appreciate the info!

I'm starting to do my research on the wiring, have any of you done the wiring for this swap? Is it as hard as i fear? or is it just an intimidating job?

thanks for the encouragement guys!

Re: 72 GMC Longbed Duramax Swap
 

I did my own wiring harness and it wasn't bad. It definitely isn't as clean as the ones you can buy (like PPE and others) but the price was right. Your engine looks like an LB7?? If so I can help you with pin numbers for hot and keyed and then you just need a tune to turn stuff off. Otherwise, you just need to get on Alldata or similar and print off all the diagrams and start going through them one circuit by one circuit and start labeling wires and removing the ones you don't need.

Re: 72 GMC Longbed Duramax Swap
 

Its an LLY actually!

and thank you so much for telling me that. Thats pretty much exactly what i wanted to hear. I think i'll give it a shot.

without sounding dumb, would it be best to pry the stuff that i dont need out of the "plug ins"? so that i can just remove the entire wire from the harness?

also

was there any thing you did your own harness that you thought to yourself "next time, i'm not doing it THIS way..."

thanks so much for your comments guys! I'm gonna need all the help i can get!

Re: 72 GMC Longbed Duramax Swap
 

I pulled out a lot of wires that I knew definitely I wouldn't need. The ECM connectors are easy to remove pins so the hard parts is removing all the wire loom and tape.

The thing I wish I would have done was to go ahead and figure out where my ECM and TCM were going to mount and route my wires accordingly. I knew where I wanted to mount them but it didn't work out so things got a little messy at the end. I also left some wires that I wasn't sure I was going to use like MIL, cruise, and stuff like that would have made it a cleaner install if I would have removed since now they are just tied up in the loom.

I'll have to look to see if there any differences between the LLY and LB7. Let me know if you have any more questions.

Re: 72 GMC Longbed Duramax Swap
 

i want in!

Re: 72 GMC Longbed Duramax Swap
 

OK!
so, second weekend in the bag!

first thing,
because the donor truck had been wrecked, the Oil tube had a small crack in it. First we had to braze the little hole.

We put up the duramax mounting plates, and polyurethane motor mounts.

Once we had the mounts on, just to check, we sat the engine in on the v8 towers. Obviously "NoGo." The Aluminum section of the oil pan was sitting on the crossmember.

We moved it around, and raised it. Figured we needed about an 1 and 3/4 inch spacer to get everything clear.

Luckily, my dad had a trailing arm from a peterbuilt that he sold about 20 years ago. It was closer to 1 and 7/8. but it works!

with the spacers, we mounted it into the stock "v8" mounting holes.

Re: 72 GMC Longbed Duramax Swap
 

We finally got everything in, but as it sat there, we could tell that A) everything was just.. in a bind. and, there was no way we were going to get the bottom of the Towers to reach the stock holes.

With a lot of shoving, grunting and cursing, we both sat and said, why cant we get these holes to line up? My buddy sat and said... why don't we just make the holes bigger? Haha!

So, we slotted all of the Mount Tower holes, so that everything could move around just enough to help everything to line up. We also had to notch the passenger side tower to make room for one of the manifold bolts.

we made a 1.5 inch spacer for the bottom of the towers out of the same trailing arm.

also, i'll have plenty of room between my tie rod and the oil pan, which was really where we were most worried about clearance.

So, to recap.

Those mounting plates work awesome, Stock small block motor mounts, Small Block Mounting towers (with a little massaging with a dremel) Stock v8 mounting holes. Using a spacer.

obviously, i'm super stoked about how this is going.

we measured, and it looks like i'm going to need a cowl hood. Or, a body couple inches of body lift.
i think i would rather not get a body lift, because of the trucks i have seen with body lifts, i'm not a huge fan. I'm open to having my mind changed!

Re: 72 GMC Longbed Duramax Swap
 

Time to clean the lens on your camera!

Re: 72 GMC Longbed Duramax Swap
 

I want to see what happens next. Donor truck 2wd or 4wd?

Re: 72 GMC Longbed Duramax Swap
 

Thanks!

Saturday morning we're going to get back at it!

the donor truck was 4wd. And i've traded the 4wd tail shaft for a 2wd tailshaft.

i did some trading, and buying with https://www.facebook.com/HicksvilleAutoRecyclers

they. are. awesome. the deal with a LOT of duramax's and they seem to be pretty reasonable too, i'm buying a brand new starter from them for 135, which sounded pretty decent :)

I just got an alldata.com subscription, and going to have to start doing some deciphering with that soon!

Re: 72 GMC Longbed Duramax Swap
 

Hey ya'll!

ok, nothing terribly exciting got done today, basically we pulled the transmission crossmember from my parts truck (interesting fact, it was my "first car" and i had it pretty much "done" when i wrecked it.)

then we cut the old one out of "old blue." Removed brake and fuel lines, and basically got everything ready for me to wash, degrease, and paint the frame!

Re: 72 GMC Longbed Duramax Swap
 

cool thread. Please clean your camera lens!

Re: 72 GMC Longbed Duramax Swap
 

I'm in, but you can update me when you see me in person.
ROBERTS.

Re: 72 GMC Longbed Duramax Swap
 

I'm definitely in for this one. Looks like a lot of fun. Harness shouldn't be too bad, I wired a 95 LT1 into my 89 Camaro, backed out all the pins I didn't need. Made for a very clean install. Good luck, and have fun!

Re: 72 GMC Longbed Duramax Swap
 

Can't wait to see future progress!

Re: 72 GMC Longbed Duramax Swap
 

subscribed so count me in on this one! :metal::metal::metal:

Re: 72 GMC Longbed Duramax Swap
 

Hey guys! Long time no see!

it's been a frustrating month starting with a transmission going out of my daily driver! Which is a 96 Olds Cutless Supreme.

Also, and any ideas would be great.
The Allison Tranny that i've got was out of a 2005 4WD truck. We talked to a junk yard, and they swapped us the 4WD Tail Shaft, for a 2WD tailshaft out of (i believe) an '02 tranny.

When we put it all together, it wouldn't tighten down. We thought maybe we had gotten something a little out of place putting it back together, so we took it to a transmission guy that we know. He said that my 4WD Sun Gear was too tall. So he ordered me a new one that he thought would fit, it didn't. I told him it was fine, and just to let me know when he figured it out.

3 weeks later he's been through three different sun gears, and a couple of other gearsets, and he calls me and tells me that "there aren't parts available to make this tailshaft work with this transmission."

My plan is to take the transmission back to the junkyard, and see if they will/can just swap me this whole transmission for another whole 2WD one.

So, we got the tranny back put together enough to use it to modify my cab!

First we had to try to get the engine and tranny leveled.

Then the white knuckled experience of just the two of us trying to get the cab on straight!

Re: 72 GMC Longbed Duramax Swap
 

While we pulled the Carpet out of the Cab, we found this "seed" receipt, or certificate from 1972!

then we cut the floor out so that the Cab would sit down over the allison using an air grinder