The Stovebolt Site Forums The Parking Lot Big Bolts 1966 GMC Crew Cab Heavy-Duty 1-ton(1-1/4 ton?)

I'm in the planning stage of building a 1966 GMC heavy-duty 1-ton(maybe a 1-1/4 ton?) crew cab dually. I want to use a 478 GMC v-6, a fuller FSO-6406a 6-speed manual O/D transmission, a dana 70hd or dana 80 rear(with 3.55, 3.73, or 4.11 gears). Because the 478 weighs a lot(925 lbs dry!) I wanted to know if a 73-91 1-ton coil spring suspension and frame are stout enough for this engine and trans. If not, I would like to know if a p-30(?) front suspension and frame would be sufficient using either the coil or leaf spring front end. I've been partial to the 19.5" wheel with the 5/10 lug on 7.25" pattern, but it's not absolutely necessary. I'm looking at using 32-33" diameter tires. I want to use this rig strictly for towing 22,000 or less pounds cruising around 65-75 mph on flat land. I plan to use this rig to replace my 86 chevy crew cab 1-ton dually that has a 454, th400, 4.11 rear. The bottom line is that I want an older GMC equivalent(more or less) of a new f-450 pickup. Any help or advice is greatly appreciated.

Mike

Long live the V-6!!

First of all I'm just a junk-yard dog. Early GMs were always over engineered. You might want to jump the spring rate up but I should think the A-arms and everything else should handle it. Think of the early(circa 1953) hemi car with those cast iron automatics. The front ends were much lighter than yours at about the same weight.
Sounds like a fun project.

Stoveboltkid,

I don't know the answer but I was eventually planning on doing a similar truck (only I am planning on doing an art deco and widening it but don't tell anyone )

So I am way stoked to see what some of the seasoned guys say here. I want mine to replace my friggen ford though, I am so sick of the dang thing. (1992 superduty crew cab :mad: )

Good luck and I look forward to this one alot! let me know how it goes.

Kendall

I'm curious what that Fuller transmission weighs too. It might be heavy.

Since there are guys out there putting the Cummins 6BT into trucks with that suspension and it weighs even more than your V-6 I don't think you'll have any trouble with the stuff working. You might need to address the spring rate as KC in NH said.

For my Cadillac 500 powered tow rig I'm using that same suspension and chose one from a big block powered C20 in part because I believed it would have stiffer springs.

Your motor choice interests me. Can you explain how you came to choose that motor? Its not known for its power output, economy or revs.

1-ton or 1-1/4 ton? Are you starting with a truck that is one of those? Or planning to build based on one or the other? If going with 19-inch 5/10-lug wheels the 1-1/4 seems more natural to me. However it may mean more work to get the front suspension and brakes setup.

What frame are you using?

Please keep posting about this truck as you conceive and build it. I'll be very interested in following along.

The 478 v-6 is within 25 lbs of the 6BT cummins. The cadillac 500 was a choice of mine several years ago and it actually weighs between 50-75 lbs more than a chevy small block because of it's high-nickel content. I chose the GMC engine because(on paper) it had the same characteristics of a 6BT cummins as far a low-end peak torque. I have towed with this engine and it's an awesome diesel! I am looking at the V-6 because the Cummins is turning into a "small-block Chevy-like" cure for a power plant and I wanted something different. I also want to build this truck to look like something that GMC would've manufactured in 1966. I sometimes feel like I was born in the wrong time period(I was born in 1977,lol).

It is heavy.
The book says:
Transmission with SAE #2 Aluminum clutch housing, standard controls, less clutch release components and shift tower. Dry weight 359 lbs.
Oil capacity is about 2.5 gallons, so about 18 lbs.
Shift tower and clutch fork/shaft is probably another 15 lbs. (guessing)
Clutch is another approximately 60-80 lb for a single disc 14" pull type.

Total installed weight, about 460 lbs.

Which is as much or a little more than my small 10 speed Roadranger...

Grigg

I was considering using a 2-ton frame from the 60-66 era instead of the 1973-1991 crew cab 1-ton frame. Any technical thoughts on this?

A 60-66 frame should fit a 66 cab and front sheet metal a lot better than the modern frame.

In general if you can't think of any advantages to changing something then leave it alone.
With that in mind, for what reasons were you considering the 73-91 frame?

Well, I'm actually building this from scratch. I want to use the light-duty(1/2-1 ton) front sheet metal. I wanted to use the 1973-1991 frame because I have a 1977 1-ton cab and chassis frame with a 84 cab to axle measurement, but I dont think this will be heavy duty enough for my needs. I also considered the Step-van frame, but I'm not sure if it'll be sufficient for my needs. When I thought about it , the 2-ton frame came to mind. I'm also debating whether the 5/10 lug IFS frontend would be sufficient or if I should just "step-up" to the solid axle 5/10 lug setup?

I also forgot to mention that I wanted the 5/10 lug pattern with the 7.25" bolt circle.

To all you metal experts out there: Would it be practical to make bends on a 1963-1966 2-ton frame to match the bends of a light-duty(1/2 ton-1 ton) so i can use a light-duty front fenders, hood, and bed? I noticed that where the cab goes on the frame, the frame is lower at that point on the lighter-duty pickups, whereas on the 2-ton trucks the frame is straight with no bends. I assume cutting and welding will be necessary to accomplish this.