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!!!

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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.

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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.

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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.

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

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Subscribing because this is awesome

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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!

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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!

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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.

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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!

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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.

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i want in!

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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.

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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!

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Time to clean the lens on your camera!

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

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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!

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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!

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cool thread. Please clean your camera lens!

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

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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!

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Can't wait to see future progress!

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

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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!

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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

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and finally sat the Cab down over everything.


i swear the engine sits like it's SUPPOSED to be in there.

We can see that we're going to have to move the fuel filter to another location, and we might end up shaving some of the heater core cover just to help make a little more room.

but! it's on there!

We were both AWFULLY excited saturday evening!

Me ( i hold the flashlight) in the black hoodie, Arlie ( the real mechanic) in gray.

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Looking good Nathan. Trevor

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Very nice! I bet you're getting stoked to drive it!

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Great job, looking good! Do you know if a stock high hump trans tunnel will work? Or do you have to fabricate one?

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Awesome, I'm gonna have to come see it.

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Hey guys!!

ok, update, but no pictures. Also! a couple questions!

I drove from Louisville to Hicksville, OH to visit "Hicksville Auto Recyclers" (facebook page: https://www.facebook.com/HicksvilleA...yclers?fref=ts) for some help with my transmission issues. They said that they do 2WD to 4WD Conversions all the time, it's also where i got my 2WD tailshaft and housing. I arrived and was blown away by this establishment.

Fellas i'll tell you what, that place was super awesome. it was a building probably... same size as your standard Kroger. Basically it's an indoor JunkYard. They deal pretty much exclusively in Duramax truck parts. I saw probably...30 engines, and probably twice that in transmissions and transfer cases just sitting on shelves. Rows and Rows of misc other parts.

they said a duramax rearend will run me about $750. The cheapest I've found elsewhere is closer to 1500.

I got to talk to one of their engine dudes, and he really helped me with some questions on wiring that i had.

I pulled the Allison out of the trunk of my car, and Jake "Stu" Sterwart helped me. It turns out. I'm ignorant, and the transmission guy that I took it to at home just had no idea what was going on inside of an Allison. Because Stu just set everything i had together, tightened it down, and boom. Everything was put together properly. I had all of the parts that i required, i just couldn't get them to fit quite correctly!

Got it home, and this weekend got the torque converter in it, and the tranny connected to the engine. So now, everything is in it.

I have to build the tranny hump. Put the doghouse on. and get the Cab (with all of the wiring) from the duramax parts truck from the junkyard next weekend.

Now my questions!

1. When you guys moved the gas tank out of the cab, What kind of fuel cell did you guys get? Did you guys just get one from LMC and call it good?

2. Those of you that have done Duramax Swaps, what did you guys do for Fuel pumps? Since i'm not using a tank/pump set up from the Parts truck, what did you guys do about your pump? also, do you guys know what kind of fuel pressure i would need? (forgive me if these are a couple ignorant questions. i figured i would start here and then move on if none of you guys had an answer off the top of your heads)

3. I can get the steering column from the parts truck, but i hate the look of a new style steering column and wheel in an old cab. Ideas? :) i recognize that it's my project, and it feels lazy to ask! but, of you guys that already did a Duramax swap, what's somethign that you did, that if you were doing it again, you WOULDNT do?

Thanks guys!!!i appreciate your suggestions and help!!

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1. When you guys moved the gas tank out of the cab, What kind of fuel cell did you guys get? Did you guys just get one from LMC and call it good?

I used the Boyd's Welding tank and added a "draw straw"


2. Those of you that have done Duramax Swaps, what did you guys do for Fuel pumps? Since i'm not using a tank/pump set up from the Parts truck, what did you guys do about your pump? also, do you guys know what kind of fuel pressure i would need? (forgive me if these are a couple ignorant questions. i figured i would start here and then move on if none of you guys had an answer off the top of your heads)

You don't need a fuel pump. The CP3 will pull the fuel from the tank. You will need one if you turn it up but the stock truck doesn't have one.


3. I can get the steering column from the parts truck, but i hate the look of a new style steering column and wheel in an old cab. Ideas? :) i recognize that it's my project, and it feels lazy to ask! but, of you guys that already did a Duramax swap, what's somethign that you did, that if you were doing it again, you WOULDNT do?

Why not use the stock column?? Is something in the way?

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Thanks!

The truck is originally a 3 spd manual transmission, and i 'm switching to Auto. From what i understand I'm going to need an auto steering column so that the shifters and everything line up correctly. Am I wrong?

I think that I must have been mistaken about the pumps. I thought that a stock Dmax had a pump in the tank, and an Injector pump that was connected to the cam gear. and that THOSE were what it ran on. Since my truck doesnt have an "in tank" pump, then i would need to add an in line pump or something to take the place of the in tank one.

as far as things in the way. So far i'm flabbergasted at how well the dmax sits in this truck!

thanks for the input!

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The high pressure pump is enough to pull the fuel on a stock configuration. I know the early Dmax didnt' have a lift pump and we have a 2012 LML at work and it doesn't either.

Gotcha on the 3 speed column. My truck was auto so I just used that and rigged a Lokar cable to make it work.

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The cp3s on most dmaxes have lift pumps built on them. Isuzu does this on a lot of their engines. There might be some dmax models that don't have the built in lift pumps, but I can't remember which they are. I've put a couple air dogs on to help for winter drivability. If you're keeping it fairly stock, you should b fine with relying on your stock cp3 lift pump.

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I would add a lift pump. Stock many if not all chevys did not have fuel pumps. On the other hand all the Dodges with CP3s have a lift pump. Most if not all of the dual feed kits for the Cummins motors run the second CP3 from a lift pump. This second pump is usually from a Duramax. Moral of the story is you are building so you might as well do it once and it is ready if you ever want more power. Loosing fuel pressure on a diesel causes all kinds of headaches! My 72 has a 73+ blazer tank in it and it works well and holds 31 gallons. I did flip it around to keep the filler on the drivers side and ran the filler up next to the stake body on the inside of the bed. It should be pretty easy to modify the sending unit for a diesel. That's my plan for when I eventually swap the Cummins in.

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Oh man you guys! thank you so much for the help!
I'm going to have to start researching lift pumps now!


also, burnin oil, is there any chance you could put up a picture of your stake pocket fuel filler please?!?

thanks again guys!

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Its not in the pocket. I cut a hole through the bed and stuck a pipe up through it. Its functional but nothing pretty to look at. I have not rebuilt my bed yet so I just run what I brung so to say. As far as the pipe a cheap way to do it is to get an exhaust shop to bend up a piece of pipe and swage the end to fit the cap part off of a donor. Its only soldered into the gas filler. Quick and easy way to install it.

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Awesome! thanks!

After doin some lookin', i think i'm actually going to go with a 69 Camaro Tank, and put the filler behind the license plate. I feel like that's a nice balance between "cool" and "easy" :) haha

Just talked to the junk yard folks today! this weekend i'm getting the Cab from the duramax truck, so that i can get the wiring and such outta there!

Also the Rearend from the Duramax as well!

Stuff's happenin' in southern indiana fellas! :D

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All this talk about Fuel pumps and such made me realize that ya'll were speaking Greek to me!

Today has been a day of learnin'!

now that i've read up on WHAT CP3 pumps and Lift pumps are/do. I realized that CP3 pumps are a gear driven pump ON the duramax engine itself. In it's stock form, this will do me fine. NOW i understand what Joel.e was telling me!

I'm going to look into some lift pumps. But may hold off until next year. Right now my goal is to get this baby on the road, and yonder budget is shrinking. a 500 dollar lift pump would go a long way somewhere else.

i really can't thank everyone enough for all of your suggestions and info. This forum is a Godsend.