Project 30 Be Low

[Mike Bradbury]

It has been 10 years since I have started a build thread, so I guess it is time to get started on my '71 C30 that I intend to slam on bags with a custom dump flat bed.
This will be a budget build as my last one was so I will be custom fabricating the rear frame and suspension and most of the front. I have so many ideas running through my head and I am sure it will morph in final result.

I drove 6 hours one way with cash in hand to dig this fossil out of the hills above Fresno Ca. with a fork lift. The body is in remarkable condition, and it has Alcoa wheels that I like although they are only 16" and I would have preferred at least 18".

So if I have your interest join in for the ride, it is going to be a slow build but it has been one I have been thinking about for 7 years.

[D-n-Tyke]

Joined

[Palf70Step]

Looking forward to watching this one

[old51sedan]

Great find, looks like it was well worth the drive. That thing just barely gets up on that trailer, good thing it wasn't a few inches longer. We like lots of pictures..

[Mike Bradbury]

Yeah barely fits is an under statement. It did not fit by about three feet. But we were already up there with no other options. U haul is the only company that rents their trailers and you can return them somewhere else. All the other companies I looked at wanted their trailer back up in Fresno.

We figured since it did not have a bed or a camper on it the tongue was still the heavy side, but it was just 36" longer than my C20 long bed. If you look close in the picture you can see that there is a 4x6 wood beam that spans the frame rails about 3 feet in front of the rear axle. We used the custom camper leveling jacks to pick the back dualies off of the loading ramps and strapped the hell out of it. It road pretty well without much sway at 65 mph. It took a fork lift to get it on the truck and some back yard engineering to get it off since I do not own a fork lift at my house.

Old51: I like to post lots of pics, and this time my build will not rely on file sharing sites like Photobucket. I will upload directly to maintain the integrity of the build.

[D-n-Tyke]

Originally Posted by Mike Bradbury

If you look close in the picture you can see that there is a 4x6 wood bed that spans the frame rails about 3 feet in front of the rear axle. We used the custom camper leveling jacks to pick the back dualies off of the loading ramps and strapped the hell out of it.

Oh geez, I had even noticed that before. That is crazy. Awesome amount of making happen right there

[kev2809]

nice find cant wait to see it slammed.

[Mike Bradbury]

Originally Posted by D-n-Tyke

Oh geez, I had even noticed that before. That is crazy. Awesome amount of making happen right there

Yeah the Dualies are just kind of floating on the ramps with only about 100# on each. We could push hard on the ramp and they would still slide in and out. The straps are more so the ramps did not slide out on the freeway rather than supporting the truck.

[cangim]

Subbed as well. Going to be a fun build it looks.

[Mike Bradbury]

I had some time to kill this afternoon so I decided to remove the seats and carpet so I could inspect what lurked underneath. I pealed the carpet back from the rockers and was pleased with the initial first peek. After I got it all out and a quick dust pan cleaning have to say this is the cleanest cab I have ever come across. If it wasn't for the gaping hole on the back this cab would be perfect. the guy I bought it from had a donor cab in the field and he said I could have anything on it except the floor pans. He needed them for a project. I cut the back window passthrough panel and called it good.

I sold/traded the seats for $500 plus a rear window. So that should pay for my new F350 seat and reupholstery.

[Mike Bradbury]

Lots has changed in my plan for the build as I have spend most waking hours mentally designing the build when I should have been doing other things.

So hunting around the junk yard I found a pretty nice 8 lug axle out of a Silverado 2500. The axle that is in the C30 now I believe is a 4.56 Eaton rear end which is really hard find freeway gears and find other parts for it so I will just sell it to some rock crawler guys and fund the build. The Silverado axle is 3.73 from first look so it will be only seals and bearings that need to be replaced not the whole third member.
Also out are the 16" Alcoa wheels for some 20" wheels that will fit around the large disk brakes. The axle is about 5" wider than the original but since I am planning a custom flat bed the width doesn't really matter as much. The extra width will actually help in designing the four link bagged suspension.

The 402 BBC and TH400 are also on the chopping block to make room for a 6.0/4L80E combo.

[Palf70Step]

It has been a while since I have seen the cut cab like that. Forgot that they had whacked them like that for the camper/motor home setups.

[Mike Bradbury]

Yeah I guess Chevy let various companies do the mods because Mine was literally torch cut rather than blade cut. Good thing the PO had an extra cab lying out in the weeds, he said I could cut a patch from it.

[SCOTI]

In & following along for the updates.

[Mike Bradbury]

So the Axle I got is the 11.5" ring gear HD full floating axle. I think this is the same as the 3500 axle. I believe the only difference between the 2500 and the 3500 Silverado is the spring pack that supports the truck. I think the 11.5" gear is the biggest, toughest axle offered in the 14 bolt housing.

Can anybody confirm this?

[SCOTI]

Originally Posted by Mike Bradbury

So the Axle I got is the 11.5" ring gear HD full floating axle. I think this is the same as the 3500 axle. I believe the only difference between the 2500 and the 3500 Silverado is the spring pack that supports the truck. I think the 11.5" gear is the biggest, toughest axle offered in the 14 bolt housing.

Can anybody confirm this?

Sounds correct to me. The FF units were the heaviest-duty for sure & I don't recall ever seeing a GM corporate axle larger than the 11.5" 14bolt.

[Mike Bradbury]

Part of the design build process is mocking up components that you have not built yet or have not purchased yet. Wheels are first on the list, making sure they do not interrupt any suspension components or steering arms. Back spacing is a variable so part of the mock up is adjusting the back spacing in various geometries.

The axle has large disk brakes and the 16" Alcoa wheels will not fit. But also the spring perches are set for a single rear wheel not a dually set up. If I shave all of the brackets off I will have to re weld new ones on and probably have to straighten the axle for an additional cost. The way I am designing the new brackets for the four bar suspension will utilize the existing spring perches so no welding will be necessary. But it will require knowing for sure where the inner wheel will be so I can design the suspension components around the wheel.

So wheel mock up needs to be simple and I don't want to spend $500 for a kit. Also I don't want to buy three or four different tires that may or may not work. So I started work on my version of a wheel simulator. A piece of 3/4" EMT and an old saw blade. I milled the saw blade with the 8 x 6.5" lug bolt pattern and 4.5" bore. Then I rolled the EMT into a 20" wheel perimeter. I will tack weld four simple stand offs at 9.5" back space and then bolt it to the rotor front and rear.

I had to turn an arbor plate on the lathe so I could mount the saw blade in the rotary table ensuring the I got the bolt pattern and bore exact.

Last photo is checking bolt pattern against the old inner wheel. I still have the bore to mill out.

[SCOTI]

Interesting.

[rickcdewitt]

Cool project!
The aam 11.5 is used with duramax and 8.1 big blocks. Its pretty stout. Holds a gallon of synthetic gear oil.is it an srw axle? You might save time getting a drw axle and its matching 6 wheels. Unless the drw hub allowed those old alcoas. Your old ho72 is very narrow. The drw 11.5 would be wider
Speaking of duramaxes,one would power this truck nicely and get decent mileage? 2wd donor trucks aren't that expensive.

[Mike Bradbury]

Yes I thought of going Diesel but a line on a 6.0 LS with a 4L80E just dropped into my lap so that is the route. I have been super pleased with my 5.3 in my '69.

I am not too concerned with the width as it looks like it will be around 5"wider in total, so about 2.5 on each side. not too bad and it is going to be a flat bed so not too much extra width will be noticed.

[Mike Bradbury]

I finished the wheel sizer enough to get a rough look at it. I still have a bit more material to relieve from the center bore but the time got late so I got it close enough to trial fit.

I had to ensure that the saw blade hub and the EMT rim were in exact alignment So I mounted them on my rotary weld table and did the measurements from there. I also turned a center hub that held the saw blade at 9.25" off of the weld table. I used all thread as stand offs for variable off sets and back spacing. Securing all down to the table it was ready for welding.

The back spacing on the dually wheels are 9.25" on an 8.25" wheel. The wheel sizer is designed to be able to change the back space and off set values. The overall diameter of the wheel sizer is 21.5" which is correct for an actual 20" wheel. I am getting a couple of junk tires from the recycler as a trial fit but a stiff donut of cardboard will suffice too.

As expected the back spacing encroaches on the spring perch. but since I am merely using the perch as a mount for a four bar suspension it should not be enough to modify wheel choice thus far.

[Mike Bradbury]

It fits pretty well except for the hub tolerance, that will be fixed tomorrow.

The pic with the red lines are the mock up of the proposed suspension bars and airbag in relation to the frame and wheel. I believe, although close to the spring perch, I have plenty of room to design a fully articulating four bar suspension.

[SCOTI]

You can always offset the link/bars (to some degree) to help clear the wheel/tire combo.

[Mike Bradbury]

The bars are going to be more constant in relation to the axle. The airbag is what I am more concerned with clearance issues. I have to factor in axle rotation not just straight up and down movement. The four bars are always going to be a set distance from the wheel once it is bolted in place. The top bracket of the airbag mounted to the frame needs to have enough tolerance to allow suspension to be fully compressed on one side and fully extended on the other.

The frame is going to be rectangle tube and internally fished at any joint and can also be jogged in at any point to allow adequate articulation.

[SCOTI]

Originally Posted by Mike Bradbury

The bars are going to be more constant in relation to the axle. The airbag is what I am more concerned with clearance issues. I have to factor in axle rotation not just straight up and down movement. The four bars are always going to be a set distance from the wheel once it is bolted in place. The top bracket of the airbag mounted to the frame needs to have enough tolerance to allow suspension to be fully compressed on one side and fully extended on the other.

The frame is going to be rectangle tube and internally fished at any joint and can also be jogged in at any point to allow adequate articulation.

Gotcha.