57 GMC / C4 Build
 

Hey guys,

Long time listener. First time caller.


I really enjoy reading through the build threads on here and wanted to try my hand at writing one for a change.



The Intro

It all started when I dragged this little heap home. She has been [strike] rotting [/strike] sitting patiently in the yard waiting for things to fall into place. Three years later, her time has come.

https://i.postimg.cc/nzvR4jWP/1-B1-A...AF54466-E9.jpg


The Truck

The title says it is a 1955 long bed GMC 100. From the looks of it she got a '57 nose job somewhere along the way. It's not in the best of shape by any means, but it is mostly complete and should suit my needs pretty well.

https://i.postimg.cc/L8XbcsqJ/049-DA...46-BD64-C2.jpg

https://i.postimg.cc/WbsK78T6/4-A792...-BFC8-E060.jpg

https://i.postimg.cc/J0LFvcJ8/2-B9-E...-F40-F05-A.jpg

https://i.postimg.cc/wBnZcdj7/30153-...1-EA0-DF23.jpg

https://i.postimg.cc/8CfnCnmD/A9-F94...551-C861-E.jpg



The Story

Growing up, my neighbor used to build some of the coolest cars in town. He worked full time at the pipe factory down the street. After work he would spend all night hand shaping sheet metal, porting cylinder heads, and calculating chassis geometry in his little one car detached garage. I would always pester him to see what he was working on and was amazed at the passion he had for the craft. The junk he would drag in there was almost unrecognizable when he was done. I remember an f100 he found out in a field that had a tree growing through the cab. He went out there with his chainsaw, chopped down the tree and drug that rusted carcass of a truck home. Another time he found a split bumper Camaro that an old barn had collapsed on. He tore down and hauled away the barn then proceeded to dig what was left of the car out of the mud pit that was left behind. When everyone else saw a lost cause he saw opportunity. I really admired that and it is something that has stuck with me to this day. For years I have been trying to talk him into helping me with a build. Besides the obvious cool factor of driving a custom truck, but also the sentimental value of having a little piece of a childhood fantasy come true.


TLDR

I'm building a truck with the help of a couple of old friends.


The Plan

A custom tube chassis c4 suspension and drivetrain.
Fuel injected Lt1
Manual trans
Dana 44 with 4.10 Gears
Ididit steering column
Dakota digital gauges
Custom bed and tailgate
Vintage air kit
Under bed gas tank
Bucket seats


The Goal

I did a quick comp of what it looks like in my head.

https://i.postimg.cc/tCNvcx2d/18-F08...25-F087-CF.jpg



Got a long way to go... :lol:

Let's get to building.

Re: 57 GMC / C4 Build
 

Best of luck, I'll watch the progress.

Re: 57 GMC / C4 Build
 

I picked up a running 94 corvette to harvest as much as I can out of it. Suspension, brakes, drive train, wiring, seats, pedals etc.

It has an LT1 383 stroker and ZF 6 Speed transmission with a dana 44 rear end.
Everything seems tight but I'll open it all up later to be sure. Also going to go with a set of 4.10 gears since the ratios are so tall on the ZF trans.

Pics

Up on the lift to pull the trans

https://i.postimg.cc/yY5mN6Qg/452-C3...-FE5-CE665.jpg


Pushed it next door to pull the motor and start deconstructing the chassis.

https://i.postimg.cc/jS7znVm8/AA7-E8...-D26-DD4-F.jpg

https://i.postimg.cc/yNC0FQz7/9598-F...-E92-D58-C.jpg

Getting the pedals and wiring. Only a found a couple of mice in there...

https://i.postimg.cc/fRGJGJHC/6-AE24...6-AB9-BC34.jpg

Stripping it down to the frame so we can get measurements for the new setup. The sawzaw sure makes a mess out of that dry rotted fiberglass.

https://i.postimg.cc/SKcJkk3h/417-A2...48-D34-A00.jpg

https://i.postimg.cc/x8pdtCJK/0544-A...-A50621459.jpg


Mission Accomplished.:metal:

https://i.postimg.cc/Zn5R83Rb/678-CE...362-EADAC9.jpg

Next step, Start striping down the truck.

Re: 57 GMC / C4 Build
 

Looks to be a good start. I’ll be following!

Re: 57 GMC / C4 Build
 

Thanks guys, I appreciate the support.

Made some progress. Got the truck all cleaned out and torn down. Rolled out the old chassis and started to mock some stuff up. I miss calculated the first time and thought the corvette k member was gong to be way to narrow.
After some cursing and a lot of research, I remeasured and the width of the corvette suspension looks like it will work nicely with this setup.

https://i.postimg.cc/vTCCXFzP/5-E083...-A3839-BA6.jpg


Also, picked up some sheet metal and bent some new bed sides. Now we can get a better Idea of ride height and fender placement.
https://i.postimg.cc/kgWP14LW/006834...90-D7-EEE5.jpg
https://i.postimg.cc/pdxbgvt4/0686-F...175-C9-F77.jpg
https://i.postimg.cc/260DQKMJ/AEF668...9-A24-C191.jpg

Decided on a 5" ride height. I like it low, but I don't want to do air ride. I think this will give me enough clearance for speed bumps and driveways while keeping the look. Going to try to keep it as flat as possible with no rake front to rear.
https://i.postimg.cc/SQZSCnps/7-E4-A...0-A99-D169.jpg

https://i.postimg.cc/6q8Dd5d2/9-F504...1134-F3790.jpg

Hopefully that's it for demo work. Now the fun part. Fabbing up the custom chassis.

Re: 57 GMC / C4 Build
 

Cleared out some floor space in the shop and got started laying out the chassis.
https://i.postimg.cc/3NhK1Gx4/E98-D7...C745-E6324.jpg

Got the frame rails all bent into shape and buttoned up. Haven't decided exactly where the cross members need to go yet. I really like his technique for keeping those easy to adjust though.

Also spent some time on the inside of the cab. Got started smoothing out the dash and figuring out what to do with the gauges. The truck had all of its factory gauges but I wanted to clean up the look. So I got a set of Dakota digital gauges for an AD Chevy and modified the dash to mount them.
https://i.postimg.cc/zGf7PPL5/44-CFD...-F97-DA313.jpg

Still need to relocate the switches. Planning to do 4 under the instrument cluster. 2 on either side of the column. I'm going to do a center console under the dash to mount the ac vents and controls. Really trying to get a minimal and clean look to the interior.

Next Step
Mount the suspension components in the frame.

Re: 57 GMC / C4 Build
 

Moving forward on the bed fab.

https://i.postimg.cc/26WBKnFC/AB6877...-AD90-D657.jpg

Set the height for the raised floor to accommodate the new rear suspension. Decided to do a shorty tailgate instead of having a step up to the bed.

Re: 57 GMC / C4 Build
 

Some progress on the suspension as well.

Set the frame rails 32" apart and the wheelbase at 113"
Got the corvette K member installed in the new frame rails. Mounted the steering rack and started to reassemble the front suspension components.
https://i.postimg.cc/nzBFq2pf/8-D25-...A7-EE7-D90.jpg

The back end was a little less straight forward.
We added some cross bracing and mounts for the batwing. Added a support to the front of the diff as well since we are eliminating the corvette c-beam. The original plan was to use the stock leafsprings on the corvette suspension and not coilovers. I've seen a few people run them this way. But, after some research and asking around it seems that the leafsprings are just really tough to get set up right. The coilovers will give me a lot more adjust-ability to really dial in the suspension the way I want it. So with that revelation we beefed up the upper shock mount and ordered a couple of different length coilover sets to see what works best.
https://i.postimg.cc/X73JcRrH/E6-F02...B0-B518-B4.jpg

Next step is to mount the motor.

Re: 57 GMC / C4 Build
 

After a lot of measurements and some debate, we decided on a placement for the motor. The idea is to get it as low and as far back as possible. We were planning to cut up the firewall anyways so we ended up using the motor mounts on the corvette K member to place the engine.

https://i.postimg.cc/XN9q5jYB/BE5-AC...393-BF7-C6.jpg

https://i.postimg.cc/MKDGs9RW/22130-...-D7806-E43.jpg

The shifter is going to be back pretty far in the cab now, so I will have to do a console and some kind of linkage to bring it forward. But, we'll cross that bridge when we get to it.

Re: 57 GMC / C4 Build
 

Spent some time looking at the dog-bones for the IRS. Was originally planning to reuse the corvette components just because I have them. But in the end decided to go with something more adjustable.

https://i.postimg.cc/0yyyh7d7/07-FA2...4370-FC6-B.jpg


Since we weren't limited by the length of the stock components, we also extended the bars to help the chassis get some more bite.

Planning to add a couple of gussets to the mount when everything gets burned in.

Re: 57 GMC / C4 Build
 

Wow, you’re making great progress. I’d check the wheel/tire placement in the front fender. They seem to lay back as stock. A lot of guys set the front tire farther forward than stock. I set mine at 115”... could of even went 116”

Re: 57 GMC / C4 Build
 

I have no business watching this but I am in. I just love all 55-56-57.

Re: 57 GMC / C4 Build
 

Good callout Jason.

We dropped the cab onto the frame to check placement and ride height. Because of the shape of the fender cutout, as you lower the ride height the wheel needs to move forward to look centered. You can see what I"m referring to in this photo.
https://i.postimg.cc/zXmvqrDg/IMG-2185.jpg

But, because we are making a custom bed I think we can move the cab back a touch to center the wheel. Then we can place the rear fenders where we want them on the bedsides and just shorten the steps as needed.

So, for anyone reading along, Jason56 is correct. 113" wheel base will be short if you are planing to use stock bed sides.

Re: 57 GMC / C4 Build
 

So the cab is set on the chassis and positioned where I want it. Tacked some mounting points onto the frame rails and got everything torqued down.
https://i.postimg.cc/FRMrFyv4/IMG-2190.jpg

The engine is mounted really far back and we had to do some trimming. to get it to fit.
https://i.postimg.cc/vmS8kRSD/IMG-2188.jpg
I knew this was going to be the case, but it was still a bit nerve racking cutting out so much. Going to have to do some more clearancing as well if I don't want to have to lift the cab every time a valve cover needs to come off.

Sacrificed some sheet metal inside too.
https://i.postimg.cc/t4k4dn33/IMG-2192.jpg

The shifter position is not Ideal. I could probably live with it if I had to, but I think I can make up a linkage to move it forward to a more comfortable spot. I know they make kits to move the shifter internally in the housing of a T56, but I haven't found anything yet for the ZF.

Still waiting on my steering column to show up, I ordered it 3 months ago. Once I get it we can mock up the pedals and reshape the footwell around the back of the block.

Re: 57 GMC / C4 Build
 

You can make a linkage like I did.

http://67-72chevytrucks.com/vboard/s...2&postcount=48

Re: 57 GMC / C4 Build
 

Nice design. That thing looks solid.

Mine gets a bit more complicated because this trans isn't a crash through. It has a mechanical reverse lock out on the shifter. Maybe I can use a cable for that, I honestly haven't thought much about it yet. Thanks for the inspiration though. That will help when I do get rolling on it.

Re: 57 GMC / C4 Build
 

There were a few companies that make shifters for the ZF corvette that eleminate the reverse lockout.

Pricey and I have no first hand experience so I cannot really vouch for either.

Hurst # 3915084
and
https://core-shifters.com/products/h...ant=9123739651

Re: 57 GMC / C4 Build
 

Thanks for the info.

Looks like those shifters just eliminate the lockout.
That is a possibility, but makes me a little nervous.
I'll have to try some different configurations to see what works and report back with my solve.

Re: 57 GMC / C4 Build
 

Steering column finally showed up... :metal:

Got it installed and all hooked up. Had to play with the angle and adjust where it goes through the firewall to get the pedals to fit. Pedals are mounted and centered on the column, its tight but everything feels right.

https://i.postimg.cc/brNpthv4/F527-C...1-C6-C4242.jpg

Bolted in the drivers seat from the C4. The thin back makes it so I can actually lift my leg enough to work the clutch pedal. But man is it ugly. :lol:

https://i.postimg.cc/Kz5mjzmn/DDFBA4...992-E7-FDC.jpg

https://i.postimg.cc/j5TsRNYx/C4-B1-...0-DEC28-EC.jpg

I scored a set of seats out of a cts-v thinking they would look more at home. With the added bonus of an integrated shoulder belt. They were way to thick though. I could barely squeeze behind the steering wheel let alone work the petals. These cabs are deceptively small inside. I removed the headrest and shaved a couple of inches of foam off the back of the seat to get a bit more space. Still going to need some work to be functional though.

That's a problem for another day. Going to get back to working on the bed so I can feel productive again.

Re: 57 GMC / C4 Build
 

Some Progress on the bed.

Placed the fenders on the new bed sides. Because of the short wheelbase I'm running, were going to have to take a couple of inches out of the steps to get everything to line up.

https://i.postimg.cc/L6pjGQbw/98-C4-...-B84-CA074.jpg

With these proportions, the fender looks a bit too long to me. I think I'm going to section a few inches out of the area behind the wheel well and shorten it up.

https://i.postimg.cc/jS8NwxSY/7-D1-B...69681-EDE7.jpg

Got the mounting points built and the bed secured to the new frame.

https://i.postimg.cc/15rDScxt/98-D16...68838-C0-B.jpg

Next step is to figure out what to do with the tailgate, roll pan and rear bumper area.

https://i.postimg.cc/FHF3Hdmx/D3-F41...-AE94-C6-B.jpg

Re: 57 GMC / C4 Build
 

Made some more progress on the bed.
Rolled some custom mini-tubs and got those installed. 4" was enough to give me 1" of clearance on the back side of the wheel. I didn't end up narrowing the corvette rear end so I am running the stock offset wheels. I haven't picked out the final wheels for this build. Hopefully I didn't limit myself too much with this offset.

Got my new tailgate built and placed where I like it. Also mocked up the bumper I bought. It is going to need some work to get it to look good on there. I was a bit surprised to see that was curved like the front bumper. Looks like they were from the same stamp except for the license plate notch. Not sure if I bought the wrong part or if this is how they are. The truck didn't have a rear bumper on it when I bought it. I guess I'm going to have to cut it up and straighten it out. Luckily I didn't spring for the chromed bumper because I figured it would need some work to get it to fit right.

https://i.postimg.cc/cCMtsZbj/88-E93...-C65-F4-ED.jpg

Got the steps tacked back together as well.

https://i.postimg.cc/J0WBVtPZ/170-B8...C06496-CDF.jpg

Something about that detail that just ties the whole truck together and makes things feel more connected.

Re: 57 GMC / C4 Build
 

Looking good! You’re making great progress.

Re: 57 GMC / C4 Build
 

Thanks Jason. Every time I think I am making progress I take a step back and realize how much work still needs to be done. It's like eating an elephant one bite at a time.

I did get some more work done on the bed. So I'm pretty happy how that is coming along.

I ended up sectioning 4" out of the fenders. It was a little tricky with the taper but after a few tries I got it figured out.

https://i.postimg.cc/tCpVBZ1H/6-EE24...2-F4-EF568.jpg

By shortening the fender I created a gap between the bumper and the back of the fender. Not sure how I want to deal with that yet. I was considering extending the bumper to meet the fender as it did before. But, now I am thinking of doing a panel similar to the step to fill in that area.

https://i.postimg.cc/66RdjxYC/1-AE14...B7-FA43-CA.jpg


I cut some reliefs in the rear bumper and straightened it out. I'll shorten it up once I decide how it should meet the fenders.
https://i.postimg.cc/Jhnn9j89/71-C65...C3-E4-A783.jpg

Also made a roll pan to fill the space under the shorty tailgate and frame a license plate.
https://i.postimg.cc/wTX7J6Fb/83-B25...97-A447341.jpg

Rounded out the bed rail corners and notched them for the tailgate.
https://i.postimg.cc/Ghw4HBPy/E59050...DC518480-A.jpg

Also got the fuel cell mounted.

Re: 57 GMC / C4 Build
 

Nice work...Jim

Re: 57 GMC / C4 Build
 

Quick update on the rear end. Got the bumper all chopped down. I think it is going to look pretty good with everything in place.
https://i.postimg.cc/5yG86BzN/16-B6-...-A018-D520.jpg

Rounded out the bottom of the stake pocket too.
https://i.postimg.cc/L5hz9Cnb/B4-FB7...CB61-C4342.jpg

Started Building the frame for my tilting bed floor as well. I'll post some more info on that next week when it is further along.