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'78 K30 Brushtruck Build - The General Purpose Rig

206K views 486 replies 92 participants last post by  posford 
#1 ·
Fair warning, this build is going to be pretty tame by Pirate standards. My goal is to build a useful, relatively practical, comfortable, capable, bomb-proof working truck. This isn't just a toy, and it will never ride to the trail on a hauler. It needs to be able to pull a trailer, skid logs, haul firewood, be reasonably pleasant, comfortable, and legal to drive, durable, relatively cheap and easy to maintain using off-the-shelf parts where possible, and as capable off-road as I can make it while sticking to those requirements. In other words, a truck that may not be the best at any one thing, but that can serve many different purposes. The "if you can only own one truck" truck. If you're looking for a linked, boatsided, tube-chassis truggy with welded diffs, half doors, no windows, and a fuel cell where the bed used to be, you might as well keep looking 'cause this ain't gonna be that. Really, it's a pretty plain, simple old school build in a lot of ways, but that's what I want. Also, you can probably fairly accuse me of building a cream-puff, but after years of running hashed, tweaked, body-falling-off-the-frame-rusty old junk, I'm sick of it. Maybe I'm getting old, but I want to wheel in something nice, comfortable, and solid. With working fawking air.

So enough with the disclaimer bullshit; here's what I started with:

It's a '78 SRW K30 w/ 400/TH400/NP203/14-bolt/D60 with no options and 7,100 miles on the clock. It runs and drives literally like new and everything on it works (pump, generator, rollers, spotlights, etc...).
 

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#2 ·
Some pics of the teardown and the sorry old '76 it will be replacing. Goldy's a bit rusty. Welcome to saltland...
 

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#3 ·
This may take awhile, we have a country internet connection that would make most Afghans laugh. Anyway, everybody's seen a truck stripped so I'll skip to the buildup. I cut all the fire fighting shit off. It had pipes and sprayers all over the underside along with both huge bumpers to remove. It was ALL welded on. I blasted the frame, welded in three tubular crossmembers, and prepped for paint (I dunno why the first pic is blue; that camera is complicated like the space shuttle). The surface rust you see wasn't missed in the blasting; it flash rusted in minutes when I rinsed the acid prep.
 

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#4 · (Edited)
The frame's painted with four coats of Rust Bullet and I've got the front springs installed. I'm using TC 6" EZ Rides, disassembled, painted with several coats of graphite paint, reassembled, and rattle-canned black. I also opened up the clamp straps and installed bolts to get some more droop out of the springs. I may end up redrilling the bolts lower; there's an awful lot of room for movement there now... I'm using ORD's HD shackles (robbed off the '76, repainted, and installed with new bushings and tubes, and all greasable hardware.

The rear springs are the 56s that came on the truck, but they're not original. They were ungodly stiff, even for 1-ton springs. I removed the 1-ton aux. overload springs and 4 leaves from each side, sanded the working surfaces, and gave them the same graphite and rattle-can treatment as the fronts. They are also mounted with greasable hardware, and I'm using the DIY4X 5" (IIRC) shackles and a homemade shackle flip. These shackles are gorgeous and stupid beefy.
 

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#6 ·
Mocking up the rear, shackle angle was not what you'd call ideal. The hangers needed moved, and I ended up doing some shuffling. For whatever reason, this truck came with some goofy, short, 6-rivet spring hangers. As a side note, as strange as it might sound, they are also hardened/heat treated steel; a file will just rattle over them. Weird. Anyway, they sort of suck because you loose a couple/three inches of drop at the front of the spring, which looses lift and increases the already increased pinion-up attitude of the rearend that you get with a shackle flip. A little of that is good, but this was looking like it might be excessive and I was worried about getting enough lift out of the back as it was. I decided to use these spring hangers as shackle hangers and find new "standard" spring hangers to replace 'em (I was just going to leave 'em and find some new hangers for the rear).

Also, those 3" blocks were factory. They even had the old style GMC logo cast into them. I won't be using them but they are in there for this mockup.
 

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#12 ·
I didn't get this one as cheap as I thought I might, but these trucks just don't exist in this condition around here. Working on it and driving it is like going back in time. The whole truck is tight, all the controls and doors and windows, etc... work like new, the dash is perfect. It drives like a new '78 1-ton. On the other hand, down south or out west, this thing would probably be considered a rust bucket, but around here, a truck this old with original rockers (or ANY rockers) is rare as hen's teeth. The only bad thing about a firetruck is it's a stripper. No options other than mechanicals. It even has a radio delete plate.

The wheels are different from anything I've seen stock. They're fully perimeter welded solid centers and look beefy. They are 16.5" x 9.75."

I like your thought process for the build. Practical yet capable. Looking forward for updates.
Thanks, that's what I'm going for.

early k30 were 2wd rear half of frame with the block as you found. and there 2wd hanger for the front mount of the rear springs . I have one also . and fyi the 4wd hanger is NOT a direct bolt on . the hole/rivet pattern is different.

and another early k30 thing I found on mine was the 2 piece drive shaft with 1 shaft 10-12" long . I swapped mine out to 1 piece and she is just fine .
I did not know that, but that makes perfect sense. The only other truck I've seen with these hangers was a very early C30 C+C. Thanks for the info.

And you are quite correct, they are (of course...) not a direct bolt on (I'm gettin' there).

And mine also had the 2-piece shaft. I'll be replacing it anyway (with a 1-piece).

I like it so far. Keep the updates coming!!
Thanks, will do!
 
#10 ·
early k30 were 2wd rear half of frame with the block as you found. and there 2wd hanger for the front mount of the rear springs . I have one also . and fyi the 4wd hanger is NOT a direct bolt on . the hole/rivet pattern is different.

and another early k30 thing I found on mine was the 2 piece drive shaft with 1 shaft 10-12" long . I swapped mine out to 1 piece and she is just fine .
 
#13 · (Edited)
Given the spring hanger SNAFU, I procured a fine new set of beautiful rust-free Cali K30 hangers from the Chevrolet scholar and gentleman Trkklr77 (thanks man!). I couldn't find shit around here that you couldn't see through, and these babies are immaculate. You fawkers got it MADE out there!

Anyway, you can see the difference between the original and the later K30 hanger. The original (early style) is on the right and the later style replacement is on the left. I also had to drill an extra set of holes because, as sweetk30 pointed out, the patterns are different but not different enough so that the bottom hanger holes can miss the bottom frame holes by much. I redrilled 'em a little higher. It'll be fine. Anything silver has been Rust Bulleted.

As you can see, I removed the stock spring hangers and the little gussets for the stock shackle hangers and painted the areas.
 

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#17 ·
Here, I ran into another little snag. I don't know how the later truck's parking brake cables were set up, but the gussets that bolt to the bottom of the frame and support the lower part of the new hangers needed to go directly where my parking brake cable bracket was mounted. Soooo... More rivet punching. Fortunately, the bolt pattern was the same, so I decided the best and simplest solution was to make the new gusset and the original PB cable bracket one piece. I cut the PB bracket to sit nicely onto the gusset and welded 'em together. Both pieces are now stronger, it'll work great, and it looks stock. I couldn't find any "before" pics with the pieces separate, but you can see (or can you? :D) where I cut the PB bracket and welded them up (you can see on one side anyway).

The last pic shows one side loosely assembled with Gr. 8 7/16" hardware and ready to go.
 

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#21 · (Edited)
Thanks, yeah, that's just up the road.

Any chance I can buy the grille off the gold gmc please?
PM'd you.


So I wanted a 1" body lift for drivetrain and tire clearance, and I wanted to stiffen and strengthen the frame. In stock form, every bed crossmember sits on and is supported by the frame rails. Normal BLs use eight small pucks to lift the bed directly under the bed bolts and leave all the unbolted crossmembers unsupported and floating in midair. This might be fine for normal use, but I've seen bed floors sag and start to cave in with BLs combined with lots of abusive hauling. Plus, it can't be too good on the bed when it's being constantly all twisted up offroad (I know it's hard on cab mounts). I haul a lot of firewood, and I wanted to lift the bed an inch while also fully supporting the floor. This was my solution. The rails support the crossmembers as stock, and the crossbars and "X" bracing even support them in the middle. One problem solved.
 

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#19 · (Edited)
Dammit, I guess I didn't take any finished pics with the hangers and springs mounted. IIRC, I set the shackle angle at 45* with the spring flexed flat. Looks good enough to me anyway. The springs are fairly flat and the shackle doesn't swing all that much through full travel. I'm sure they will settle and increase the angle a bit when I get the body back on it and build a rear bumper, and I didn't want to go too crazy with the shackle angle anyway. I need good, stable load carrying capacity; this will be a working rig as much as a crawler.

Here's a pic that shows everything mounted up:
 

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#22 · (Edited)
Just FYI, my shop isn't usually such a mess, but it's not that big and I've got everything that makes up a fullsize truck scattered all over creation. Anyway...


My other purpose with this apparatus was to stiffen and strengthen the frame. First off, any sort of cage was out due to practical/utilitarian considerations. I seriously considered fully boxing it, but I decided not to for several reasons. One, my main concern was that rust would get started in there and I'd have no way of dealing with it. I'm fucking sick of rust. Two, it would make the packaging of lines, wires, and particularly the exhaust more difficult. Even with an open C-channel, there is very little room between the pass. rail and fuel tank solenoid and the T-case for a 2.5" or 3" exhaust pipe, particularly if the T-case is tucked up a bit higher than stock. Three, it would make future add-ons/modifications much more difficult and time consuming (same reason I didn't powder coat the frame). Four, it would be a real PITA. And five, I was sort of concerned that might make it too rigid, meaning it would be very stiff and unyielding until it reached it's yield point and then it would be permanently tweaked. As we all know, stock C-channel Chevy frames may not be the strongest, but they have an unbelievable amount of spring to them. You can really distort one, and it will snap right back (more or less...). On the other hand, while the rigidity vs. yield thing is true, maybe it's nothing to be concerned with in reality. I know many trucks today are built with boxed frames, but combined with all the other factors, it was enough reason for me not to do it.

Anyway, by itself, this brace is obviously not very rigid. It is 1"x3"x.125" wall rec. tube. However, when bolted to the frame, it transforms it from two small C-channels into one giant C-channel and locks the upper flanges in place relative to each other (no bowing, no fore-aft movement which happens when the frame gets twisted). The "X"-braces also prohibit any amount of diamonding of the frame. I can hook up to one recovery point and give it hell without worrying about pulling the frame out of square.

There is also more to to the stiffening solution than just this. I'm planning to do something similar with the trans/T-case crossmember which will make the giant C-channel act like a giant tube, at least in the middle. That should significantly stiffen the whole frame. At least that's the theory, we'll have to see how well it works. And I know somebody's gonna ask, so yes, this added some weight to the truck, but it's not that bad. I forget how many feet of tube I used, but I calculated the added weight right at about 150lbs. It's tightly centered, relatively low, and all sitting directly over the rear axle. I can live with that.
 

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#25 ·
No, sorry. A friend of a friend has a mid-70s K30 he wants to get rid of, but it's a real basketcase and I'm sure the frame is as rusty as the rest of the truck.

that back bone cross member looks great cool build for sure
Thanks, it's a little different, I admit, but I think it'll work well for my purposes. Originally, I was just going to run a couple tubes on top of the rails to lift the bed 1", but then I thought, "why not connect them?" and it went from there.

I'm sure everybody's seen a 203 range box doubler, but this one came out purdy so I wanted to show off a couple pics. :grinpimp:

First, I wanted a plain, normal 1/2" NPT drain plug for the range box. I am going to use 3/8" recessed square drive 1/2" NPT magnetic drain plugs in the trans, range box, T-case, and both axles for ease of service (the external square head plug in the pic was just a test fit). I don't like having to remove a non-blind bolt to drain the case due to possible leaks, and it's so much simpler if all the drain plugs are the same and can easily be removed with a 3/8" ratchet and extension. These plugs are particularly nice for the axles since they sit flush and have nothing protruding to get fawked up or catch on shit.

FYI, I drilled the hole off-center on the pad on purpose. The case wall/bulkhead is surprisingly thick, and I had to go that far in to get out of it.
 

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#26 ·
I painted the case shiny Chevy orange. The pics show all the stock parts I will be reusing, scrubbed and ready for assembly. Those are some big honkin' gears.
 

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#27 · (Edited)
Here is the Off Road Design Doubler kit. It is very complete and of the highest quality in terms of machine work and craftsmanship. ORD may not be the cheapest, but they sell top quality, and I've never had better customer service anywhere. That adapter is a work of art and ridiculously overbuilt (which is just how I like it).

The last pic shows everything ready for assembly.
 

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#28 ·
wow props to you for going all out on this thing i probably would have jsut drove it how it was. that frame brace, um boxing stuff is awesome.

i was a emt and a few fire houses had these trucks and the one thing i always noticed is they leaked everything, puddles under everything that can leak
 
#30 ·
Yeah, that was pretty much my wife's reaction too... :laughing: When I bought it, that was actually my plan as well, but I just decided that this truck was at a place now where it could be basically made new again, but it needed work. I didn't post any real pics of the teardown or the underside, but it actually had quite a bit of surface rust started underneath, particularly on the bed. The cab wasn't bad, but it was bad enough that in five years, I'd be having serious rust issues, and it would be much easier to stop now than to be continually fixing later. Plus, considering what I wanted to do with it, tearing it apart would make the whole process way easier. This current build is just the beginning, but I want a solid platform to build on. And to be clear, it's not some sort of show or aesthetics thing; I don't care if it looks rusty, but of course the problem is rust doesn't just stop. It will slowly eat the whole goddam truck if you let it, and I'm tired of having to lift my door 6" and line it up with the striker by eye before I can shut it.


Here's the rangebox all buttoned up and ready for installation. I know the pics are getting ridiculous, but DAMN, that is just sexy! Is it wrong when heavy duty drivetrain parts get you to half-mast? :grinpimp:
 

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#29 ·
Here is the low gear, intermediate shaft, and bearing installed into the adapter housing, as well as the assembled case.
 

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#32 ·
Here's the cast iron factory adapter cleaned, painted, and installed, and a couple shots of the installed rangebox. The crossmember is just temporary, but the box is ready to rock.
 

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#33 · (Edited)
I guess I forgot to mention it, but I obviously dropped the engine/trans back in it. I used DIY4X's HD motor mounts. I haven't got any pics of em, but they are nice and beefy.

I'll probably swap the headers over from the '76 because I'm going to be reusing that exhaust, but otherwise, I'm going to just run the motor bone stock for now. The trans is stock except for a TransGo shift kit, B+M deep cast aluminum pan, and I'll be running a large cooler and remote filter. An engine and trans build is on the agenda at some point in the near future, but for now, I just want to get the frame, suspension, drivetrain, and body work done. I am also going to do both axles, but again, for now, I just need to get the restoration part finished and get the truck running again.
 
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