Project Large Marge - Going Full Tilt

[Just-in-credible]

Well, I got the itch to build a new project…again.
After building my Tahoe chassis swapped 1960 Apache last winter, I thought I was going to be done for a while. But we all know how that goes. The winter got cold. I got to daydreaming. And here we are.

So…what did I drag home? Her name is Large Marge. I think it is a 1975 Chevy tilt cab. And I have to say, I am in love with the thing. It has a 427 tall deck BBC, with a 5 speed manual transmission.

I put a lot of time into 3D modeling how I want to build it and what I want to do, and I 3d printed little 24 scale models of how I want it to sit, and how long I want the frame etc. I have a pretty good vision of what the final product is going to look like.

The overall idea is to use junk yard parts wherever I can. I want to shorten the frame to about a 100” wheelbase, and stuff modern medium duty axles under it. This way, I have modern disc brakes, modern tire options, decent gearing etc. I will probably go with a dana S110 rear axle, and a D700F front axle. I want to run modern 10 bolt hub centric wheels, and run 22.5 or 24.5 Alcoa style wheels.
For suspension, I think I should be able to bolt on an international IROS rear air suspension, or a Kenworth air glide, or something similar. From my limited knowledge, it seems like this stuff should all bolt together. The heavy and medium duty world seems to have a few relatively standard dimensions, like 34” wide straight frame rails, and everything sems to bolt together. The shock mount, the air bag mount, the arm, and everything seems to bolt on. I am thinking with the relatively large bags from a big rig, I should be able to toodle down the road with fairly low pressure in the bags and have a decent ride.
The front might be a different story, but I am pretty sure I can make the same concept as I am using on the rear work for the front. Use an OEM style arm and bag mount, and bolt it all to the axle. It might be a bit more complicated than that, but I think it should all work.

I probably won’t run it super low, but with the air system in, I want it to be able to sit it down on the bump stops when I am parked and be fairly low. I measured it all out, and I have a ridiculous amount of room between the top of the tire and the inside of the wheel well. I think I have about 15” of room that I can lower the thing. I am thinking that the clearance between the tire and inside of the fender will not be the issue, it should be frame to axle clearance, which, I have somewhere around 12-15” as it sits right now. Keep in mind, this is with a 42” tire. I will probably run something much smaller like 32-36” range.

For the engine, I will probably just keep this engine in it for a little bit while I focus on the rest of the drivetrain, and eventually swap in either a modern big block or a diesel of some sort. I would love to put in something fun like a DT466 or an 8.3 Cummins, since I have all the room in the world and will not have to worry about length of the motor.

So this is the plan in which I am going to tackle the thing
1) Chop off the dump box
2) Chop off the tag axle and clean up the rest of the items on the frame which are not required such as the PTO and hydraulic assembly. At this point, it will be short enough and low enough to fit in my shop. I only have an 8’ door, and I think she sits right at about 8’ right now, so I will have to do some trickery to get it inside. Plus, I like doing the dirty work while it is outside, so I have less cleanup to do when I have it inside.
3) Put in a modern style clutch master and slave.
4) Fabricate a hydroboost brake master
At this point, I will probably try to see if I can get the engine running. I know myself well enough to know that I will 100% try to drive the damn thing around the yard once I get it running. And I feel like I should try to get the clutch and brakes working BEFORE I do that.
5) Install the new rear axle with air bags
6) Install the new front axle and suspension
7) Install round style aluminum fuel tanks
8) Install Exhaust stacks
9) Drive it for the summer.
So that’s the plan! I will try to keep this up to date as I build.

The cab of this thing is a bit rough, so if any of you out there know where a really clean cab is located, I would be super interested in it. The cab is the same from 1960-1980. So if you guys could keep an eye out for me, I would greatly appreciate it. Also, I am new to the whole medium and heavy duty world, so if anything I am planning does not make sense, please let me know.

[Just-in-credible]

Hauling it home was a bit of an adventure. Lets just say I may have been a tad bit over the capacity of my equipment. I was about 28,000lbs truck, trailer and everything going down the road. We weighed the trailer loladed at about 19,000lbs.

Needless to say she is a heavy beast! We did not weigh the truck and trailer empty, I really wish I would have. But I plan to weigh all the scrap that I hack off of the thing, and weigh it once I have it on the road, then I will have a good idea of what it started out at. I figure the trailer was probably about 4500lb, so I think the truck was somewhere around 14,000-16,000lbs. I had originally figured it would weigh like 10,000, but I quickly realized I was a bit shy on that once I saw how beefy everything is on it.

[Just-in-credible]

This is my vision for what i want it to look like in the end. I tried a few different colour combinations and a few options with a bed, vs no bed, and a few different wheelbases. I am still a bit up in the air, but I think I am down to a plan that I like.

I picked the wheelbase in these models because it will fit a standard cab and chassis flat deck, if i ever want to put one on. Cab and chassis trucks are usually the same 34" wide straight frame rails. which is the same as the truck currently has. The decks typically come in 2 lengths. They are either 60" cab to axle, or 84" cab to axle. the 60" cab to axle is usually a 9' long bed, and the 84" is an 11".

I think the thing looks a bit too short without a bed if i do the 60", but just right if I have a bed on it. I think that the 80" just looks too long. So for now, I am going with the 60", and planning the build from there. If i can find a decent used deck on marketplace or something, I'll pick it up. but for now, I will probably just throw a sheet of steel over the frame rails, and call it good.

THe models are made with a 22.5" alcoa style wheel, a 36.6" tire, and using 24" diameter, 36" long fuel tanks like the 80ish gallon ones from a peterbuilt or something similar.

If mymodelling skills are correct, that should put the bumper, the fuel tanks and the cab about 7" off the ground at ride height, with the ability to drop another 3-4"

[Just-in-credible]

I made my 3D models so I can move the axle and other components in 6" increments forward and backward. The blue and green truck in this picture are with the 80" cab to axle dimension, plus a little space for the cab to flip.

The orange truck has the 60" C/A spacing.

The longer wheelbase would probably ride a bit nicer, but I think the short version looks a lot cooler.

[gentrysgarage]

Always wanted to do one of these! I will be watching!

[Just-in-credible]

Well I got to work this weekend on step 1, getting the dump box off.
Keep in mind, she is still far too large to fit into my tiny little shop, so I need to do all the cutting and hacking outside before I can bring her inside. I measured it up so I know how much I need to hack before she will fit.

I have an 8’ tall door, and she sits about 8’2. It should be able to come up with some sort of plan to get the front to sit a bit lower. I would love to pull a leaf or two from the front, but I am a bit hesitant to put the front on jack stands of any sort outside. I might just put a chain from the from to the axle and put a ratchet binder on to suck it down.

And I only have about 21’ total in length. She’s currently about 26’ long, so I have a bit of chopping to do.

I rented a gas powered chop saw from home depot, so I could cut the large panels a bit smaller so they would be more manageable. The front and rear were no big deal, but the sides were pretty heavy.
I used a pry bar to lift the panels up, and I just let them fall.

[Just-in-credible]

Step 2- Chop, chop, and chop some more
When I had the saw, I cut lines across the main deck so that I could use my cordless grinder and a zip disc to get it into smaller pieces.

My first step was to cut the sides off. The box had a set of two main rails running parallel above the frame, and I figured I should probably keep these for some sort of project at a later date. I may build a gantry or something out of them later. I cut the sections into somewhat manageable size to drag around.

[Just-in-credible]

Next step was getting the hydraulic dump assembly disconnected and getting the bed rails off.

Of course, thew one day I could actually line up some help for this, it was a nasty snow storm. Oh well…we bundled up and got at it.

I had a few issues with the hydraulic cylinder that holds pressure on the tag axle. It was in the way of being able to slide the deck off, and of course, it was rusted in place, and no amount of beating or swearing could get the thing loose.

I ended up using a tall bumper jack, and some dunnage to get the assembly jacked up high enough to where we could pull it from the side. I hooked on with a chain and pulled it off with minimal fuss.

I don't know how much this thing weighs...but I know it is a LOT. and I am glad to have this step over with.

[Just-in-credible]

Then I moved on to cutting the tag axle out. This was pretty straightforward, other than the fac that these frames are super stout, and have all kinds of funky bracing above the axle assembly. The bottom of the C channel is boxed in with some 2x2 square tubing, which, as far as I can tell, looks like it was factory.

It was no match for the old zip disc though. I got it all hacked apart in no time.
As a side note, I recently bought a little winter beater car, and I caught a LOT of flack from everyone at work about it. Especially because it has a goofy looking little tow hook in the front. Having said that, I decided to see if it could be useful and pull things around the yard. And wouldn’t you know it…the thing actually did pretty good! It was way more maneuverable than my truck, and it is awd, so it did not struggle at all.

[Just-in-credible]

And this is where I got to. The rear tag axle is out, deck is off, and now I can actually start to see the vision a little bit. The rear leaf suspension is a bit odd, so I ended up cutting the rear hanger out. It would somehow use the tag axle as a support for the rear leaf spring. After cutting the tag axle out, I did not have a rear hanger anymore. But that really did not matter, since I do not plan on driving it anywhere like this anyhow. In this picture, I just have a piece of dunnage between the top of the leaf and the bottom of the frame so I had enough room to work. I will pull that out and just let the axle sit on the bump stops when I move it into the shop.

[Just-in-credible]

Still in the rip apart phase of the project.
I got the fuel tanks off, the PTO pump and dump valves removed, all the gear for the brakes on the tag axle, and did a ton of grinding to cut unnecessary brackets off.

I also figured out how I am going to get it in the shop. As I mentioned earlier, I only have an 8 foot tall door to my shop. And I think Marge sat at about 8’2” if I measure correctly.
I got the ass end to sit down nice and low by cutting the rear hangers off the leaf springs, and letting the frame sit on the bump stops. The front was a bit of a different story. I used a chain and ratchet binders to suck the suspension down. I think I gained about 6” by doing this, and I now measure it to be about 7’9 or 7’10”. So I think I am good to go.

[Just-in-credible]

This was my solution to get the front end a little bit lower.

[Pick121]

Originally Posted by Just-in-credible

Well, I got the itch to build a new project…again.

The cab of this thing is a bit rough, so if any of you out there know where a really clean cab is located, I would be super interested in it. The cab is the same from 1960-1980. So if you guys could keep an eye out for me, I would greatly appreciate it. Also, I am new to the whole medium and heavy duty world, so if anything I am planning does not make sense, please let me know.

This popped up on my FB marketplace feed, it’s all the way in Northern CA, USA but maybe worth a look? Of course depends on “roughness” of your current cab compared to this! Those dark spots that look like bullet holes are probably moss/lichen barnacles they will wash right off
https://www.facebook.com/marketplace...ibextid=wwXIfr

[Just-in-credible]

Thank you! that actually does look like it is in a bit better shape than the one I currently have, I reached out to the guy. I wonder if the guy would let me take just the cab? I guess we will find out!

[Just-in-credible]

The last little bit, I have been working on the brake and clutch system. My initial plan was to go to the junkyard and grab a hydroboost and master from a 2006ish tahoe/suburban. I also wanted to use a modern style hydraulic clutch. The original set up had the combination style clutch and brake master that most of these trucks had. Instead of having it on the firewall like most pick ups do, the master was mounted under the cab and pointing backwards compared to the standard orientation on a pick up.

There is a nice little plate with threads welded in where the old master was located, so my thought was to make a simple plate to bolt to this attachment point, and bolt my new style clutch and brake master to this plate.

[Just-in-credible]

As soon as I got going on this, it became immediately obvious that this was going to be more of a challenge than I had intended. The space I am trying to cram this assembly into is very small, and conflicts were everywhere.

My first step was to design up a quick little plate, and print it out of plastic on my 3d printer. This allowed me to really quickly change or move things to where I need to move them.

[Just-in-credible]

The first thing I found, the hydroboost hit the frame when I closed the cab. So I moved it up slightly. Next step, the accumulator hit the radiator. I flipped the hydroboost 180 degrees, and now the accumulator was hitting the clutch master. I printed a new plastic plate with slotted holes so I could move and adjust things to see where everything could go.
Once I got the location figured out, I then had the reservoir hit the cross brace, and the stud that holds the master to the booster was also hitting the brace.
I got that figured out…then the master hit the power steering pump. It had a goofy style of power steering pump which I have not been able to find much information on, and it was mounted in a goofy location way outside the frame rail, so I decided to convert it to a standard Saginaw style power steering pump with a normal location. I have ordered those parts off amazon, and that has solidly landed as a future me problem to deal with later.

[Just-in-credible]

I went to my local pick n pull and was able to find a few different styles of masters and reservoirs to use which solved some of my packaging problems. I pulled one from an 06ish Van, which has a matching master, but have a much slimmer reservoir, which was enough to solve the problem of the reservoir hitting the brace. I also have a much shorter and slimmer style of master from an early early Duramax truck, so I will see if I need that.

The picture with the three masters shows the difference. The one on the left is the one I had kicking around from my tahoe/apache chassis swap. You can see it has a very bulbous tank. The one on the right is from the van. The master is the same, but the tank is slimmer. And the middle one is from the early duramax truck. I had to do a bit of swapping around to get the right combination of exactly what I wanted. Some trucks had the little nipple, which I did not need, some had smaller tanks with other attachments. But in the end, I was able to mix and match to get these arrangements. I took the shorter early master apart to see if there was a difference internally, and they have the same diameter bore and mostly the same guts internally. So in my mind, they should be more or less the same capacity.

[Just-in-credible]

you can see...it is a tight fit

[Just-in-credible]

I then designed and 3D printed a few linkage adapters to get the clutch and brake hooked up and see if it would work. I will make these out of metal later, but for right now, this will work to just get it to the point where I can bleed the system and maybe burn a donut.

Everything hooked up and lined up like it should. I used 3/8 heim joints from amazon, and I had to get a bit creative with the hydroboost linkage adapter to be able to offset the linkage and provide adjustment in the end. But I made it work.

[Just-in-credible]

I then started running brake lines, and surprise surprise, brake lines hit the frame, and hit the alternator belt and who knows what else I am hitting.

Long story short…this has taken me a LOT more thinking and adjusting and adapting than I thought it would. But I am slowly making progress.

[Just-in-credible]

IN this picture, you can see the strange looking power steering pump located low by the frame, with the giant hose up to a high mounted reservoir. It makes it challenging to mount this stuff because I can not see the conflicts when i close the cab. THere is just literally no room to get in and look. It seems like I have miles of room when the cab is up, but when I flip it down, everythign hits everywhere, and I cant see what or where the problem is. I usually end up putting my phone down where i think the problem is, hitting record for a video, then closing the cab. It is a slow process, but it works.

[Just-in-credible]

Now that I have a rough idea of where the brake and clutch masters are going to live, I started bending up the lines.

I used some rebar tie wire to make a quick template of where I wanted things to run, and then brought the whole assembly onto the bench. I figured it was a bit easier than trying to bend the whole thing in place.

I also 3d printed some clips to keep the lines nice and parallel. These were a huge help in keeping everything where it was supposed to be.

[Just-in-credible]

Also, you can see in the picture, I had a series of bend gauges for my tubing. I stole this from a guy on YouTube called hot rod hippie. He gives a full description on how to make them and how to use them. If you are making your own hard lines, I highly recommend checking this guy out, as he is a really great resource.

[MellowYellow70]

I like this project, keep the cool updates coming.