Maxwell Garage Service Truck
The first question that must be answered before beginning any project is what do you expect it to be when you are finished.
I've spent a fair amount of time thinking that through. When completed this truck will replace my recently totaled modern 1-ton pickup. It will pull up to 7,000 pounds easily from start-up to freeway speeds.
Safe stopping is a priority, including the ability to stop a loaded trailer even if the trailer brakes fail.
Comfort is important, at least in that I want to sit comfortably for hours at a time staying fresh enough to drive safe and function effectively at both ends of a trip.
This truck needs to carry tools and chains, jacks and binders, and all the supplies for loading cars and trucks on my trailer. And carrying at least one helper is a good thing.
This project is based on a '55 GMC 1-ton I bought as a parts truck. It will have a big utility box to carry tools. I'll create bedsides under the box either using standard fenders over the tires or maybe using side rails from a flat bed to dress it as a flatbed with tool boxes instead of a modified slide in tool box.
The engine and transmission will be a Cadillac 500 with a Turbo 400. I don't really like the sound of a Diesel motor. Its more a preference than anything else, but I'd rather hear a big gas powered V-8 than a pinging Diesel. Plus when I thought through the cost going gas just made more sense.
The big Cadillac makes as much as 500 foot pounds of torque in factory trim and does it turning slow enough to live under hard use. I would suggest comparing the horsepower and torque specs of the late 60's Cadillacs to those of the early Cummins 6BT used in Dodge pickups. The Cadillac compares favorably.
The last year Cadillac put these motors in cars was 1976. I have two of the motors, a '75 and a '76. By changing to an aftermarket cam shaft and intake manifold I expect to regain most the power these later motors give up because of emmissions tuning.
I've almost completed the installation of the IFS from a '72 C20 with disk brakes in front and have installed the GM 14-bolt from another 1-ton under the rear.
The GM 14-bolt rear axle has the 10.5 inch ring gear and full floating hubs and is one of the tougher axles used under light trucks. They are common, easy to work on, and use bearing and brakes parts that are readily available.
This one has 3.42 gears, which will allow the truck to run 75 mph with the motor running about 2800 rpm and that is about perfect. The rear came to me under a 1950 Chevy truck that I bought for parts.
Other planned features will be power leather bucket seats, tilt column, power brakes , air conditioning and AC power.
The tires will be Michelin 265/75-16's on wheels which I've not yet bought, but which I expect will come from a 3/4-ton Dodge from about 2000.
As I write this the frame is setting in the shop with the GM 14-bolt rear axle mounted under it. The IFS is in place lacking a few bolt holes and some bolts of being complete including the power steeting box.
1955 GMC 250. Chevrolet would have called this a first series but GMC
didn't mess with that foolishness. Original motor was a GMC 248
which was gone when I got the truck. Original Transmission was an
SM420 granny gear 4-speed.
GMC's of 1954 and 1955 had a very different dash than Chevrolet's of the same years.
Trial fitting the Cadillac 500 into the truck before the cab was removed.
GM 14-bolt rear axle mounted under the truck.
The lighting makes it hard to photograph. The strings are determining
the centerline and confirming relationship of various points on the
frame. White patches on the floor are spots where I have marked frame
positions on the floor.