Questions on capacity of truck.

me0418840987 · Nov 14, 2011

I have what I currently belive is an 84 GMC C 60. At least that is what the title and vin are for. That is what I was told it was when I bought it a few years back.

I decided that since I got home in the daylight today, I would go to the local pit and get some TB for the driveway, as winter is coming, and the ruts are bad on the plow tractor. I told the loader operator to load until the helper leaves were touching their stops to make sure I was not overloading the truck too bad. He did, and I thought all was well, until I scaled out. Turns out I had just shy of 11 TON of TB on the back- put me north of 33,000 lbs. What gives, the C60 is only rated for 24,800 according to the door jamb plate. No big deal, as I was only 3 miles on 45 mph backroads from the house. The helpers were JUST touching, no squatting anywhere but the tires- G load 10:20 Goodyears from a garbage packer truck. I have never been able to make the helpers touch with a full load of asphalt shingle tear off, and a full heaped box of that only puts me at 29,000 or so.

Anyone with a C series truck and knowledge of them would be helpful, as I would like to know how to find out what I really have. I belive the cab was swapped, because It is way too nice for a 27 year old WI truck-almost completely rust free.

Diamondpilot · Nov 14, 2011

I maintain basically the same truck, a 78 C60 for a local landscape company. Its a 350 2 barrel with a 4 speed and split rear end.

I have driven it numerous times hauling fire wood, gravel, ect and I know his is something like 24000# GVWR with a empty weight just north of 10,200# leaving 14,000# or 7 tons capacity legally. I can not say for sure right now but its placarded on the dash. From what I remember its sitting just about like what you describe when I use it but the helpers are not quite touching yet at this load. Its been June since I have used it or worked on it much other then a front brake job and new bearings.

Chris

me0418840987 · Nov 14, 2011

Mine has a 366 4 barrel, 5 speed, wish I had a 454. Drove one once, and it went like crazy compared to mine. Scales empty at 11,680. Goes pretty good when empty, left the rear in low today, and ran it home no faster than 40. What is the bed length on yours, mine is a 16' with 3.5' sides. This truck is nice to drive, but, I liked my 74 IHC 1700 345 gas 5 speed split axle better. Seemed to have more low end grunt where it counted, and was much less fussy than all of the electronic distributor crap on my 84. My 84 will just fry a dist cap occasionally and die on the road with little warning, yes there is a cap and rotor and a gallon of oil behind the seat all the time. Lesson learned after I had to chain it fully loaded to the mechanic, because he doesn't have a truck heavy enough to legally drag it in. I pulled it in with my dodge 1500.

Verticaltrx · Nov 15, 2011

We have a '75 C60 that is also rated at somewhere around 24-25K GVWR. It only has a 350 and 4spd, but has a 9K front axle and 23K rear axle (2spd), and double frame. I think the GVWR was based on the tires that originally came on the truck, as the rest of the truck is capable of hauling much more. I'm sure they also de-rated them to get under CDL weight.

When I haul rock, gravel, shale, etc I generally load it until the overload springs just barely touch. This is a little over 10 tons generally giving a gross weight of about 32K. We have farm plates on it so it is exempt from the weight restrictions and I'm generally only going a few miles. You can tell it's a good load, but the truck handles it fine.

Also, I saw you mentioned you left the rear axle in lo range. If you don't already know how to do so you need to learn to split shift it, especially when hauling that much weight. It will pull the load a lot better when using the proper gear as well as being easier on the clutch.

Diamondpilot · Nov 15, 2011

The one I use only has a 8 or 10' bed. With the 350 2 barrel its a pig. It would not run 50 mph empty. It also has the 9K front and the 23K rear but is just so under powered.

He also has a 76 Ford F-700 with a 491 and a 5 speed. Its a split rear axle and has a Holley 4 barrel on it. Its twice the truck the GM is and is much more reliable but looks worse overall so most paying jobs he takes the GM.

Chris

tcartwri · Nov 15, 2011

It is likely derated because of the brakes on it, not the springs. If you don't have to roll across a scale I wouldn't worry about it at all.

me0418840987 · Nov 15, 2011

Also, I saw you mentioned you left the rear axle in lo range. If you don't already know how to do so you need to learn to split shift it, especially when hauling that much weight. It will pull the load a lot better when using the proper gear as well as being easier on the clutch.[/QUOTE]

I can split shift just fine, but this truck can't anymore. It used to split shift just fine, but as it sits quite a bit, less than 5,000 miles a year, the splitter motor does not shift fast enough to effectively split shift. I'm sure I could remove the splitter motor, and clean up the internals, but....oh well, it still works and no time.

And as far as brakes, I have front and rear disc on her, she will lock up all four corners with 5 ton on

Diamondpilot · Nov 15, 2011

Disc brakes would be nice. The C60 I just did brakes on and drive from time to time has a old style master cylinder and drum brakes. They do work but you need to pump them up.

In the last year we put a new master cylinder, all new front wheel cylinders, new shoes, and drums serviced.

Chris

me0418840987 · Nov 15, 2011

I guess they are factory, as the mason who has the 86 with the 454 engine, also has identical disc brakes on the rear of his. Correction, his is a c70.