GMC 6500 Meduim Duty Truck

tessiers · May 1, 2017

I just bought an old GMC 6500. It has a 366 (or maybe a 427 how do I tell the difference) v-8, 5 speed with 2 speed rear, 16' silage body. It was an old fire truck, has under 25000 miles on it and is as clean as your gonna see around here, with the salt and such. The guy I bought it from says he hauled 6-8 tons of grass to a load, which is great for what I want. My question is this, I would like to also haul 800 lb. 4x5 round bales with it along with a 12k equipment trailer I have. I figure I can get 19 bales on truck and trailer, compared to 10-12 on my 1 ton with same trailer. What do you all think, good idea? or just stick with the silage and 1 ton for hay? My problem is always drivers, I figure with the big truck I can cut my trips in half and not deal with helpers. Plus I think it will do the truck good to be used a little more, setting is worse than running at some point. My next issue will be adding a hitch, the body hangs out about 3-4' beyond the frame, not sure what the hitch will look like and still clear the body when it dumps. Any pics or ideas would be appreciated.

Diamondpilot · May 2, 2017

Hitch will be a issue.

Fuel mileage will also be about 6 mpg.

tessiers · May 2, 2017

Last Year I put 1700 miles on my one ton, fuel mileage will not be a major concern. It takes a lot of trips at 5 miles to a trip to run up mileage. I am thinking something like the wheel lift on a heavy wrecker, maybe 4" square tubing like an oversized receiver hitch.

RedNeckRacin · May 2, 2017

If you are not worried about the speed limit I don't see why not. Those gas motors were not known for keeping up with traffic loaded. The hitch is going to be the biggest issue though. Might want to check into the stingers before you get to excited.

Stimw · May 2, 2017

I used to LOVE driving the old 5 and 2 vehicles!
Once you get the hang of how to shift them you can keep it in the power range.
If it still has the shift pattern chart check it out so you understand it.
One of the quirks in the pattern was you shift 2-lo, 2-high, 3-lo, 3-high, then 4-lo to 5-lo then 4-high, 5- high.
And of course first is granny gear.
Then there is shifting the 2 speed without the clutch.

Looking4new · May 2, 2017

Does your engine have a vacuum advance? If so from what I read it is a 427.
Watch out with them 427s, if you over rev it you will drop a valve. Ask me how I know.
The shift pattern previously posted was called a 'short 4th' pattern.
Most of my Chev truck experience was with 5x4 trannys. I preferred Ford Louisvilles 800s and 880s over the Chevs.

MossRoad · May 2, 2017

This might help on the engine I.D.

There's an explanation at the top, and a section for big blocks towards the bottom of the link

Reference: Chevy Engine Block Casting Numbers - Chevy Hardcore

BrinkME · May 4, 2017

I'd build the hitch off of the dump body frame ... think along the lines of a reinforced drop step bumper at the rear of the dump body, obviously not so low that it hits when dumping.

like this ... please excuse the crude drawing.

Looking4new · May 5, 2017

I think, legally you should build the hitch off the frame of the truck and get a longer tongue on the trailer. It is either that or shorten the box, then build the hitch.

civilian · May 5, 2017

Can you make a separate hitch frame that slides in and out, being pinned in either position? Would take some exact welding, though. Thinking that you would slide it out fro trailer use, and slide it in for dump use. Just a thought. Jon