'72 C3500 GMC flatbed project

[JJorgensen52]

Time to start a project thread!

I bought this truck, in theory at least, to use as a work horse so my K10 can get new floor pans this summer

The truck is super clean - all original, needs outer rockers and not much else. 50,800 original miles, factory flatbed and original 350/4bbl/4spd/PS/PB

The day I bought it:


First thing was to replace the rusty hood with a good spare it came with:



And some rattle can

[JJorgensen52]

Next up: New fuel lines, pump, and filter. Found this in the fuel tank:


Was a little bit distressed by how rusty the tank in general and the sending unit are. I ordered a new sending unit and stainless fuel lines from Inline Tube.

Can I swap a '67 fuel tank for this '72 no vent model? I'm going to have a clean '67 tank available to me shortly.

This is how I left off for the day

[JJorgensen52]

And now to my current status: new rear wheel seals!

I am entirely new to the heavy duty (H072 in this case) axles, so this was a bit of a learning curve:



Driver's rear drum, both shoe hold-downs were missing so replaced those and adjusted, new rear wheel seal, packed and torqued bearings, all is well


Passenger's side... not so much.



That wheel seal had completely failed. Cleaned everything up as best I could, replaced the seal, packed the bearings, but new shoes are in order for that side as soon as the budget will allow. Yikes!

Also, I've now got a line on this '67 C-30 dump truck

which is going to get parted out and donate it's dump hydraulics and PTO setup to this truck

[fxdxharley]

how do you find these local? i never see them on criags list. stop over some time. now that the snow is gone i can actually get working on my blazer.

[JJorgensen52]

Originally Posted by fxdxharley

how do you find these local? i never see them on criags list. stop over some time. now that the snow is gone i can actually get working on my blazer.

You can't find 'em because I keep buying them

I'll definitely drop by sometime soon to check out the progress

[JJorgensen52]

Not much to report this weekend, waiting on parts mostly.

1. Found out the points weren't properly bolted down inside the distributor, at the expense of the integrity of the new muffler and a cold dark hour on the side of the road

2. R&R'd the heater controls and put screws through the face to hold the bracket to the faceplate - my '69 is like this as well, nice and secure now!


3. R&R'd the cowl, cleaned out 15 lbs of leaves and twigs and rotted organic matter from the cowl vents.

4. Removed the wooden bedside boxes from the frame


Next weekend I'm picking up the '67 C30 dump to get ready for hydraulics swapping into this truck

[JJorgensen52]

Parts truck on it's way home tonight - more pictures to come when I start getting hydraulics swapped over

[JJorgensen52]

No work on the GMC today, but started stripping the hydraulic lift frame of all the extra metal (IE the rusty dump body ) before I swap it across.





As you can see, this truck got used HARD


Anyway, Once I've got the lift frame stripped completely, I need to rebuild the last 6" of the rails on either side, then separate it from the '67 frame (it is welded on) and then get the flatbed off my GMC so I can swap it over and build new bolt-on mount towers for it. Tonight, I'm trying to ID the PTO ...

[MrBeast]

Sweet! I think you are at the start of a great project, I remember the thread when you brought it home.

Glad to see another dually coming back to life, there is getting to be not a lot of them left.

[JJorgensen52]

More work on the dump mechanism:

You can see a bit here, there is a bend in the actual piston, which I'm working on straightening out (I loose about 4" of return travel)


Both sides of the dump subframe were rusted through on the outside where the mudflaps / center frame brackets were mounted. Cut all that out and ready to weld in some new plate tomorrow (Hopefully)
Driver's (You can see a split in the inside wall of the frame tube as well, rust growth between the bearing block and the frame caused that. I am going to weld the split and then weld a doubler plate over it before I patch up the outside)

Passenger's


Removed the uprights, working on getting the pivot bar unseized from the driver's so I can fix the rust at the end of it



And my second or third major setback of the day - the pivot bar on the hydraulic cylinder failed! This is a 1.5" diameter steel rod - I will have to weld in a replacement. 30 years with no grease will do that


Here's the broken end still stuck in the bearing block


That's all for tonight, don't like to run the grinders at night and tick off the neighbors.

[MrBeast]

I'd just take that ram to a local machine shop and have them make you a new rod for it. Shouldn't be all that expensive and will be well worth it to have it done right.

[JJorgensen52]

Originally Posted by MrBeast

I'd just take that ram to a local machine shop and have them make you a new rod for it. Shouldn't be all that expensive and will be well worth it to have it done right.

I'm getting a quote for that from my local hydraulics service place, new rod and renew the seals, etc.

Didn't make much progress today. Weather is being non-cooperative!

Driver's side of frame - split welded and fished, patch welded in place for the bottom of the frame.




I have new hardware for mounting the ram, and most of the metal needed to rebuild the uprights and the subframe.


HOWEVER - design snag!

Turns out that when they installed the dump bed on the '67, they cut 17" off the rear of the frame to make the dump angle as it should. Since I want to keep the original flatbed and frame dimensions, that's no good.

Nearest I can figure, if I shift the subframe back when I mount it to the GMC, I can still achieve a 50* dump angle with the current cylinder and geometry if I lengthen the uprights and taper the rear overhang behind the pivot. I'm going to make up a model of this later on and make sure everything works out.

[MrBeast]

You know seeing that thing a bit better, I would honestly scrap the mechanism and rebuild it, with that much rust in it, I would not trust it, and the steel to build that wouldn't be all that much.

Some box tubing and a little time, probably less time than you would spend fixing everything that is wrong with that one. I think you would be much better off, much safer too.

[JJorgensen52]

Originally Posted by MrBeast

You know seeing that thing a bit better, I would honestly scrap the mechanism and rebuild it, with that much rust in it, I would not trust it, and the steel to build that wouldn't be all that much.

Some box tubing and a little time, probably less time than you would spend fixing everything that is wrong with that one. I think you would be much better off, much safer too.

You know, I thought about it. The tubing is structurally sound (there's not even any surface pitting), with the exception of that one spot on each side which trapped moisture. I'm confident in the strength of the metal once it's been repaired.

I do appreciate the input, though. I guess it's just the yankee in me, hard to scrap things

[JJorgensen52]

Finished patching up the subframe today and got it separated from the original chassis



With all holes drilled and primed

[JJorgensen52]

Spent most of today out and about, so not much work got done:

1. Got the seized rear pivot shaft free - had to cut a relief in the housing and spread it a bit, this pic was taken after I'd finished welding it back together.


2. Just a shot of the poor PTO pump - the slip joint in the shaft seized up and caused the u-joint to chew into the packing retaining screws.


3. The herd at rest!

[JJorgensen52]

Had today off so I made some great progress today:

Uprights are completely repaired and I've extended both sides so they're now 110" in length to match the original flatbed. I tapered the tubing from 4" tall down to 2" tall behind the pivot point, in order to be able to maintain approximately a 55 degree max mechanical dump angle without cutting off the rear of the truck's frame.






You may note I have not yet added the reinforcement plates to my extensions - I ran out of flat stock so I'm going to finish that off in the AM

Got the ol' John Deere involved to lift the flatbed off - this assembly is extremely rigid by itself, I was quite surprised!




Truck chassis with just the wooden carry blocks and brackets remaining - those come off tomorrow for subframe fit-up. Turns out the wood spacer blocks have some dry rot at the bottoms near the frame, so I will be using them as a template to cut new ones from PT lumber.

[JJorgensen52]

Lots more progress today:

Naked dually


Subframe and bed installed with straps for mockup








Clearance at rear of frame at full height


Started cutting down original bed - frame mount brackets to fit new subframe - decided to retain bolted configuration rather than channeling and welding.

[JJorgensen52]

More progress

Naked Dually


Lift frame with all deck mounting brackets fitted and tack welded


Mounting brackets (haven't made new wood spacer blocks yet)



Subframe mounted to chassis hopefully for the final time



Lift frame in place with all brackets welded (also added fish plates, no pics though)



Setting the deck back on ... clearly this is why I bought a tractor


And all put back together.


Next thing to tackle is a rear hitch / bumper and lights, and getting the hydraulics all squared away. The silver is a cold galvanizing compound - this was a new product for me to use and I'm very happy with the results thus far.

[JJorgensen52]

Progress has been slow. I've found a good SM465 PTO, I've been working on the hydraulics slowly but surely, but mostly I've been worrying about trailer wiring.




Rear lighting back in place and with sufficient slack to let the bed tilt fully



Bulkhead connector I'm mounting to the firewall for all the trailer brake wiring




You may notice some other terminals in the background - I'm tapping into the factory harness at the rear harness firewall connector and the stop lamp switch, replacing the terminals and using wire from another harness I cut up, so in essence it will look as if the factory installed the plug in connector for a brake controller inside the cab.

[JJorgensen52]

This post describes what one of my good friends calls "OEMitis" ... I did all the in cab wiring today, which was done to make it look as if the factory did it.

First connection (for the brake controller) - stop light switch.
Before

After


Rear harness firewall connector - after shot, connections for turn, marker and reverse


Main harness reloomed - new trailer harness connector is the 6 connector black right in front of the gas pedal



Thru-bulkhead connector carrying lights (4 wires), ground/power/ brake feed from brake controller (3 wires)




Used a factory marked drill point and knockout in the insulation to install it, just like they meant it to be there


Bulkhead connector with mating harness connector attached


And the new fender mounted junction box, which connects the rear trailer harness to the bulkhead connector and houses the 2 self-resetting circuit breakers (30A for brake controller and 20A accessory feed to the trailer)



The loose black and white wires are power and ground, I ordered a special jacketed cable for that purpose but UPS is still trying to find it...

Tomorrow the hitch goes on, as will the rear trailer connector, then an oil change and fuel sender and first trailer towing tomorrow afternoon!

[JJorgensen52]

Little update here, haven't really done much with the truck other than use it!

1. Hydraulic cylinder is out for repairs, I have the PTO and all cables, getting ready to complete that install and then redeck the bed

2. Did some towing. This thing pulls my 6000lbs tractor/trailer combo like my K10 tows a 750lbs boat. So nice!

[JJorgensen52]

First time in ages I've had a chance to work on this truck!

Bad cell pic (camera is on the fritz)


I got the new rod cut for the cylinder, welded on a new pivot point for the piston, relocated the pump to the truck's frame and got a new subframe cross member and brace welded in.

Hopefully tomorrow I will get the PTO installed on the trans and get the pump hooked up - then I just need new hydraulic lines and the bed can go back on for good.

[JJorgensen52]

Progress update!

Hydraulic ram is rebuilt, pump moved to frame and replumbed:



Bed lowered:


Bed lifted (not under power yet, no PTO driveshaft)


PTO installed


And an unexpected hangup:


The rear brake line on this truck was fitted to a standard 1/4" brake tee - which cracked and started spraying fluid everywhere. Come to find out, the reason it cracked is because the factory line is not a 1/4" brake thread at the axle, after all. Unable to find the right parts, this '92 S10 Blazer rear line and 3/16" - 1/4" adapters worked out just like GM meant it to.

As soon as I get a PTO driveshaft installed I need to run the control cables, then redeck the bed

[JJorgensen52]

Driveshaft fabricated (at least a temporary home made for now)



Unfortunately, the driveshaft is rubbing on the parking brake cable arrangement, so I am going to have to rearrange that linkage to make everything work.