The Stovebolt Site Forums The Shop Area The HiPo Shop 54 GMC150 service truck, frame/ suspension.

This is my first post on this forum, I really hope I'm doing it right.

My project is a 1954 GMC 5 window, hydramatic service truck. It's been sitting in AZ for 50 years and really pretty rust free.
The bed is a 1947 utility bed made by American Coach and Body work of California. It's 60 inches X 90 inches X 43 inches, all steel. I estimate it weighs at least a 1000 lbs.

My goal is to make this a classic, functional service truck. One I can safely drive on the freeway at 75mph to Home Depot then to the job site. I don't need it lowered, it's not a "corner carver." This means stronger engine, power steering, brakes, A/C and overdrive.

This is where I need the collective wisdom of other bolters! What works well and what should I avoid?

On-line, the S-10 frame swap is the popular option. That may be fine for a 1/2-ton show truck, but I worry that a 3/4 ton with a heavy service body is not a good match with an S-10. The existing frame is excellent, so leaning that way. What about front suspension and steering? Mustang II with power rack and pinion? A Camero sub-frame? Just add power steering and disc brakes to the existing axle? What do you recommend??

Look forward to your responses?
Grrroger in AZ






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By far the easiest and most cost effective method is to rebuild the stock system adding PS/PB to the existing axle. There are lots of kits available to use. In order to achieve your 75mph goal a engine upgrade is probably in your future along with a rear end swap.
The other option and a bit more labor intensive is a frame swap with a modern 3/4 ton. There are challenges with the swap to make it look right but you see it at the Rod Meets all the time, so it can be done. Good luck.

I'd agree with Martin. The easiest route is to keep what you have and just make it better with an electric p's unit and a brake booster.

Don't fall prey to the myth that trucks of this vintage can't be driven at speed because they don't handle well. They handle just fine at high speed with radial tires and properly functioning steering and suspension.

Adding an electric p/s system and a brake booster is pretty easy compared to cutting the frame and adding a whole front clip with discs and IFS.

As for disc brakes, don't assume they'll shorten your stopping distance. Adding them may even increase your stopping distance. Four wheel drum brakes are used on dump trucks and tractor trailers for a reason. They work.

You're only benefit to adding disc brakes is that they won't overheat as quickly if you're standing on them while coming down a mountain or if you make hard stops in quick succession at high speed a la auto cross racing.

I drive my unrestored and unmodified 1950 3100 on the interstate every week. It tracks straight and true and can handle curves without excessive body lean. Of course with a 216 I don't get over 55 too often but if it was capable of greater speeds I wouldn't hesitate to drive it faster.

Check out the project journal by Barnfind49 before you make up your mind seems like good route to me anyway.

A 1954 GMC 150 with Hydramatic is just as rare as a 1954 Corvette but unfortunately the collectability value is much much less.

This is rather encouraging!
I was definitely under the impression that 75MPH was not sustainable with the original 54 steering, especially mine. It has about an 1/8 of a turn of play in sitting on dry ground! Upgrading steering was already in the plan.

I've never done an electric power steering conversion before so need to learn more. Does it just assist your existing system, or does it replace it? I'm upgrading the motor to either LS or small block and that factory box is in the way of the exhaust manifold. Any recommendations on an electric system?

I had no idea a 54, 5 window, hydramatic was that rare, I should treat her with more respect now that she's that special. She's already bringing our family closer together which I love. At Thanksgiving My son (43), grandson (11) and myself (old), 3 generations, all assisted in pulling out the existing motor. I have to say, my eyes watered up a couple of times..... I blamed it on dust.


The hydramatic is long gone and somewhere in her history, probably 55-60 years ago, someone hacked in an old 265 chevy small block. It was done with heavy channel and angle iron welded to the frame. Also some really cheesy motor mounts, I'm in the process of trying to get all that swap stuff out without messing up the frame. it's a challenge!
GRRROGER

The unique value went with the engine/transmission. What you have now is just like the rest of the ‘54 GMC’s.

A motor, tranny (overdrive) and rear end was always in the plans. I read an excellent Tech Tips that describes an easy swap to a 4:10 ratio. I've been looking for a donor rearend and learning they are few and far between.
I spent some time in a salvage yard yesterday and found 3 trucks with what appear to be Eaton rear axles. They were all 1960-65 trucks with 4 speed transmissions. How can I determine what the rear axle ratio is by looking at a rear end, especially if there is no ID tag on it? These were all in trucks sitting on the ground maybe with a wheel or two on them, access is very difficult. They want $350 for the 3rd member and no guarantees on the axle ratio, you get what you tell them to pull. Recommendations?

Turn the driveshat and count the number of revolutions it takes to turn the wheels one revolution.

I second this advice. Barnfind has some expertise in swapping LS engines. his 49 looks stock from the outside, he even retained the original transmission. A lot of your questions could be answered by just reading his project journal.

The 4:10 were only in the automatic trans trucks.

Well I guess I'm the bad apple in the bunch.

June 29, 1956, President Dwight D. Eisenhower signed legislation funding the construction of the U.S. Interstate Highway System. The 50's trucks at that time were designed to take much poorer roads than today, at speeds driven at less than 50 mph, on roads that had no posted speed limit, because nobody was crazy enough to try. It wasn't till the late 50's early 60's that the "need for speed" became a marketing tool for selling automobiles. The V8 engine was created to push these heavy cars along because the 6 cylinder was simply running out of legs.

The frames on our trucks are designed to flex. The suspension is stiff on purpose for farmers (for example) doing field work, going through ditches, riding over rocks and hitting deep pot holes. The same truck navigating today's modern expressway traffic at 75 mph is like a "drunken sailor" trying to walk down a sidewalk. The body makes the truck top heavy and the body roll is scary. It's white knuckle driving. You have to drive slower than the current traffic flow, anticipate the need to panic stop sooner and watch for the nutters that try to cross traffic in front of you. The coffee in your cup holder is on the floor and your seatbelt (if you have them) is straining to keep you in your seat.

Modern frames are stiff and their suspensions are designed to handle modern roads, respond to make the passengers comfortable, while negotiating rush hour traffic.

Here's a section from the Tech Tip (um, That I wrote, BTW ) that explains what donor truck to look for:


If the truck is a two-wheel drive C-20 with coil springs, 99% of the time it will have an Eaton HO52 rear axle. If it also has the automatic transmission, it probably has the desired 4.10 center section. 

All one tons/C-30’s have a leaf spring rear. And many of those have 4.10 HO72 -- especially the big block trucks.

All Chevy k20 trucks (4-wheel drive) use leaf spring rears, and most of those will have the HO52.

Two- wheel drive leaf spring Chevy and GMC trucks 99% of the time use the Dana 60 rear axle -- these center sections will not interchange with the Eaton axles . K2500 GMC trucks use the Dana 60 also.

The 4.10 HO52/72 was standard with 350 auto trans 4x4 and 4x2 trucks and was optional on all 3/4 and one-ton trucks .

All HO52 and HO72 housings are the same, 47-72. Same axles also. Four different hubs, though: 47-70 single wheel and dual wheel hubs are different offsets; 71-72 are the same but they have 9/16 studs.

All HO52/72 rears can use any year of brakes. So a dual rear wheel rear brake system from 72 bolts in place of a 47 DRW system. Plus, almost all 14 bolt from 73-2006 brake system will work also. Wow, so you can ditch those Huck brakes at the same time ...

One last thing -- a lot of these HO52/72 rears have Detroit no spins (AKA “Lockers”). If the axle has a tag on a pinion bolt, it has a factory no spin. It will also be called out on the spid.