Newbie C65 owner

[Jim Timber]

Hi guys.

I just found this place looking for info on my new to me 1975 C65 former pumper truck. The previous owner took the tank and pump off, so it's missing the carrier bearing and I'm going to cut it down and put a dump box on it anyway, so the frame's getting cut down shortly and I'll deal with the driveline then.

30,011 miles on it. 366ci, 5x2 manual, 10R20's, 6.5 and 8.85 rear end ratios

Just thought I'd say hi.



That's my FIL in the photo. He was looking at the rocks in my taconite tailings. Old fart keeps making off with my driveway!

[mrolds88]

Hi Jim, Looks like a fun build.

[Jim Timber]

Should be.

The guy I bought it from was going to do the conversion and add it to his fleet, but ended up finding an International 5yd truck that needed some paint and got it. This one has been sitting for about a year since the driveline was dismantled, so I might need to go through the carb to get her running right.

P.O. has a 5yd box and all the makings of the wet kit I'm buying from him, and he's got a big payloader to set the box with at his place - he's agreed to help with that when I get the chassis ready and running. I can drive it over and we can mount the bed (it's on a subframe, so that should be easy), then I'll drive it home and get the hydraulics working. I'll be able to raise the bed with my tractor to gain access to the frame.

How hard are the frame rails to drill on these? I'm guessing cobalt bits and some cutting fluid to pilot? Do I need to rent a mag drill, or will I be ok with a regular 1/2" and silver-deming's? I'm a machinist, so this isn't too far out of my wheelhouse, but I haven't put a file to the frame yet to see how hard it cuts (it's at my land about 110 miles from home).

This weekend I hope to get the rivets cut off and at least free the spring hangers from the frame. I'm just going to grind them and punch them through.

[mrolds88]

Dont know how god/bad it will be to drill. I wouldnt think too bad. I'd start with a good bit and cutting oil and see how it went. Your first hole should give you a good idea. As far as your rivets go, I would take a cutoff wheel and put an X on the rivet heads then pop the heads off then a 1/4 at a time. If you cant get to them with the cutoff, drill them down to the base of the head and drive out. I usually replace them with a bolt one size up. That way you know the bolts are tight in the holes.

[Jim Timber]

I've cut rivets out before, and planned on using a cutoff wheel. I don't feel like driving my acetylene tank 2 hours in the back of the Tahoe, and I'm less enthused about driving it on my open trailer.

Are these half inch rivets, or are they bigger? I've read the current upfitter's best practices, and they say to max holes at .750, but then say the rivets are .620 (5/8") in a .660 hole and that doesn't make sense to me unless they mash the rivet to fill the loose side?

I don't recall how big the rivets I cut out of my 1/2T's were. It's been a few years since I moved anything structural on a C-frame.

[mrolds88]

On 1/2, 3/4, 1 ton stuff they used 3/8" rivets. Holes are a bit bigger, I'd say in the neighborhood of .390 to .400. I drill them to 7/16" Not sure what yours has in it, but I would think 1/2 wouldn't be out of the question. In order to keep things tight in the holes, if they are 1/2" you will probably have to go to 5/8" bolts. I use grade 8 flangebolts whenever possible. Try flangebolts.com

[junkmandan3]

Medium duty trucks such as yours usually have frames in the neighborhood of 40,000 psi. OTR heavies are 100,000 psi and higher .

[Jim Timber]

So this'll be like working with stubborn mild steel. Should be a breeze!

Thanks guys!

I'm working on my stump grinder the next few days, then I guess I have some cabin repairs to do for the FIL up north from the sounds of things. It looks like the truck is getting delayed a bit.

[Jim Timber]

I didn't do much with the truck this weekend after all. I put the new plate on the front, noticed the gas tank is empty (not entirely a bad thing), and measured out the 118" for the frame bob.

The cut mark is just aft of the front spring hanger.

So something came to mind when that point was found - the rear of the frame rail is narrower from top to bottom than the belly of the frame. So if I just move the rear hanger's forward, the axle will change it's angle relative to the ground and the pinion will point "up" more. Is this a bad or good thing?

I'm used to dealing with lift kits, although it's been a good 15 years since I modified a suspension. We always had to make the pinion poke up more to straighten out the driveline, but I do remember that being aimed up too much was not desirable.

Will I need to wedge this to correct the angle, or should I just see how things work out when I get it skooched forward? The other thought is that I'm not going to be running this thing more than an oil change a year, so it might be moot.

[mrolds88]

That depends. Do your front hangers attach directly to the side of the frame or do they wrap under? If they wrap, then yes you'll have to wedge your axle. It would also raise the back of the truck.

[Jim Timber]

The front's are going to be on the same plane as they've always been. It's the rears that might end up lower, which would raise the rear end.

This has 24,000# springs in it (27,5 GVWR), so I was thinking about removing a leaf or two anyway just so it rides a bit better.

[1976gmc20]

Most people just cut the frame behind the cab and add/remove a section to change the wheelbase, rather than messing with spring mounts.

[Jim Timber]

I'd rather mess with spring mounts than weld the middle of the frame.

[1976gmc20]

Originally Posted by Jim Timber

I'd rather mess with spring mounts than weld the middle of the frame.

Okay ... I'm just telling you what truckers that I have known and worked for have done in the past.

What's good for a Peterbilt ought to be good for a Chevy

[Jim Timber]

I was taught to never weld on a frame by a bunch of diesel mechanics, however that's not the issue at play here (Chevy's upfitters best practices gives numerous methods to do it correctly). This truck is 110 miles from my shop, and I have no flat surface to work on it up there, nor do I have an existing 240v outlet (I could install one if I chose to). But getting the frame cut and welded back together straight given the working conditions is the main concern.

I can rent a mag drill and put the hangers back in perfect alignment in a day.

[Jim Timber]

After doing some geometry, I'd lose a lot of spring travel if I moved the spring hangers forward and lost the narrow frame tails. So I'm going to cut the middle out of the frame after all.

There's an internally braced section on the left frame rail where they put a 1.5" hole too close to the bottom flange (likely to do with the water pump, as this was a tanker). The repair/compensation looks to have been done well, but I'm going to remove that part of the frame when I shorten it.

I won't have more than a 120v mig welder available, so I'm thinking of just making some bolt on connector plates inside the C and adding part of the removed frame rails to the outside which will get me to where I can drive it the 110 miles to my home shop and weld it with the big mig per the GM best practices. The frame is 5/16" thick - well beyond the capabilities of my little flux core toy.

Which leads me to the question of how long should my bracing be over the splice? GM states no less than 6" either side of cut, but what's ideal? The piece of angle that's added now is probably 18" or better. The dump body sub-frame has connections at 16" behind the cab and forward, and again at 32" rearward. I'm hoping I can tuck my splice in between those, but if I can't it's not a big deal.

I know I mentioned not having a flat place to work on this up North earlier, but I'll be able to move it 1/2 mile up to my FIL's storage place to use the concrete pad there as soon as his pontoon is put away for the season. I'm hoping that's soon. It was supposed to be done last week.

Any input/advice appreciated.

[Jim Timber]

According to this, I should make them as long as possible.

http://trailer-bodybuilders.com/dist...s-truck-frames

[El Dorado Jim]

any new pics on the truck?

[Jim Timber]

Nope, it's still parked where I left it this fall (unless it's been stolen), and currently -8F outside.

I do have one that's got a little different angle, but it's not a pic of the Chevy alone.

[Jim Timber]

I did get another cross member with the hanger bearing mount, so I can get the driveline back together and drive it down to my house for the shortening, but that'll happen when it warms up this spring and the snow is gone.

We're in hibernation mode for the next couple months.

[Jim Timber]

I forgot about this one too. This was when I first agreed to buy it.

[El Dorado Jim]

thanks for the pics, I , or should I say my wife has a '74 C65 dump truck, it is an old DOT truck,it has a 5spd, with 2spd rear end, I had the engine rebuilt a few years ago, it has a 427 tall block in it with a holley carb....it has air brakes and a weird air power steering system,seems to work alright, just usually they have normal, power steering I think,what is in your truck? I will post pics, seems to be an interest in these old trucks....

[Jim Timber]

I'm pretty sure it's just a regular hydraulic drag link set up.

[El Dorado Jim]

what engine and trans do you have? 2spd. rear end? air brakes?

[Jim Timber]

5sp, 2sp, and vacuum assisted hydraulic brakes. Pretty normal configuration for the 366.