It’s time to wrap up my recent obsession with GM’s ill-fated foray into IFS for big trucks. We covered the really big semi “crackerboxes” here, with their air-ride IFS, and the steel tilt-cab. But I’ve saved the best for last: a genuine curbside Chevy C80 to really show off its independent underpinnings. And what a gem it is; I fell in love with this dump truck, even if the operators of them didn’t so much at the time, causing GM to dump the IFS for a conventional beam front axle in 1963.
It was announced with great fanfare in 1960: “The biggest improvement in trucking in decades!” Independent torsion bar front suspensions across the line. It was classic GM of the era; the same year the Corvair arrived. Advanced engineering was the key to GM’s continued growth. The problem was that invariably, all these new technological miracles appeared before they were adequately developed. To revolutionize the truck field with IFS might have taken quite a few years of field testing. (CC’s post on the 1960 pickup IFS is here).
Here it is in great detail. It all made so much sense, at the time.
And more detail. And I’ll be showing you my own pictures of it too.
What could go wrong? Well, I’ve been unable to find exactly why GM backed away from this design within three years, but there’s several clues: A number of design changes for 1961 and 1962. These are some made in mid-year 1961.
And some more made for 1962:
There’s no doubt that weaknesses in the original design arose with the first year. There’s just a lot more to go wrong here, than the very tried and proven solid axle with leaf springs. Alignment issues, breakage and wear on components, tire wear from camber issues, and who knows what else.
Trucks live a hard life, especially so dump trucks that invariably have to go off-road into rough ground and with a heavy load. This will quickly reveal the weakest components.
Or just hauling a load of new Chevys.
Already in 1962, a heavy duty solid axle suspension was an option, although only on the tandem-axle M80 series, as pictured above.
This is a single axle C80, the highest capacity rated truck Chevy made except for the M80 tandems. Which is to say, it wasn’t really all that big of a truck (GVW 25,000 lbs), but a size that was popular with contractors and fleets due to its relatively low cost yet fairly high capacity.
Here it is, still on the road almost 60 years later. Obviously a few of these held up. The control arms on the larger trucks are solid forgings.
The other side. Looks to be a bit of mud in the mix. Those are some beefy looking ball joints on the steering gear.
Here we can see how the torsion bars are connected to the upper control arm.
The two-speed rear axle is suspended conventionally. I bet the sound emitting form that exhaust at full chat is something to hear.
I came very close to popping the hood on this one, to get a shot of the engine.
The standard engine for the C80 was the 348 “W” big block V8. With a four barrel carb, it was rated at 220 gross and 180 net hp. And yes, these numbers were trustworthy. The 348 was considerably revised in 1962, as it now shared cylinder heads and other changes with its bigger brother, the 409.
The 409 upped the ante a good bit, with 252 gross and 215 net hp. I’m pretty sure our feature truck has the 348, but I wish I knew for sure.
Here’s what it would have looked like if I had opened the hood.
The ’62 cab’s big change was the new simpler and flatter hood, dropping the controversial twin pods of the ’60-’61s. It still had the dog-leg windshield, and would until 1964.
If one didn’t know better, it would be easy to assume this was the cab of a pickup. There’s not much to give away that this was a serious truck. The Spicer five speed’s knob has gone missing. The button for the two speed axle is there though. As to the lever on the column, no, it’s not for a second transmission. I’m not exactly sure what it is; perhaps a trailer brake controller? Someone here will know.
This cab is familiar to me, as I spent a fair bit of time in a C60 flatbed that a construction firm I worked for in Iowa City had, along with some other trucks. It had the small block V8, and man did that little V8 rev its heart out, for a truck engine, especially compared to the Fords. Less displacement, but pushed hard, it would keep up with them.
The C80 did deserve its own instrument cluster, with an optional tach and air pressure gauge, if air brakes were specified.
The levers on the floor operate the dump bed, whose hydraulic pump is drive off a PTO from the transmission.
That’s what this truck is all about. And I sure could have used it back in the day when I was hauling lots of loads of excavation dirt and fill rock, with a rental truck. This would have been a fine alternative. Just the right size.
And I would have had that Jet Smooth Chevrolet ride too!
Postscript: I forgot to mention that this truck has either had a ’60-’61 grille swapped in, or it is a ’60-’61 with a newer hood. The ’62 grille had single headlamps.
More GM Truck IFS coverage:
1960- 1966 Chevrolet Pickup Trucks: The First Modern Pickup VinceC
1959-1961 GMC DLR-8000 Crackerbox – GM’s Deadly Sin 32
1960-1980 Chevrolet Tilt Cab trucks
And one on the 348 and 409 V8 Engine
Was there any resistance from fleet operators as well? Would the extra grease nipples on the IFS might have annoyed the large fleet operator?
I get why you’re taken by these IFS trucks. I always love the idea of someone trying to do a familiar job differently, and here, undoubtedly better for ride purposes. Alas, the extra expense is practically visible, and not just for the user.
Those revisions for ’61 seems pretty substantial to me: maybe GM had undercalculated to save some coins, and perhaps that made the complex-looking arrangement (compared to leaves) a self-fulfilling prophesy of failure for those wary initial commercial buyers? Mind, your photos clearly show it could be made to last for a good 60-odd years, so there’s that.
A side-bar, I wonder why the 348 and 409 had such short strokes for the bore? Seems at odds with the application for trucks, though ofcourse piston speeds would be slower (for longevity), which was something mentioned/calculated even in car road-tests back when.
Slight further digression, I’ve just been reading about the marvellous Merlin from RR. At 27 litres, it weighed 1300 lbs – can’t help noticing these old lumps here weigh 800. Hehe!
Great find, this big old girl. That hefty but friendly Bull Staffordshire styling makes it really hard to gauge the size compared to the shrunken relatives.
Cabs and hoods were common between the smallest half-ton version and these, which is why Paul’s picture of the cab’s interior makes it look so pickup-ish. Fenders were similar, though flared on these heavier duty ones as there was simply a wider front track to accommodate.
As for height, figure the entire step area in the last picture is over and above the smaller versions. Tire height will also obviously play a factor in overall height.
Length? Wheelbases on this model ranged from 157″ to 193″.
Here’s where I pulled some of this from: http://www.oldcarbrochures.org/United%20States/GM%20Trucks%20and%20Vans/1962_Trucks_and_Vans/1962-Chevrolet-Truck-Models-Brochure-R-1/slides/1962_Chevrolet_Truck_Models_R-1-04-05.html
Wow! Same head, bigger dog, huh.
I wonder why the 348 and 409 had such short strokes for the bore? Seems at odds with the application for trucks, though ofcourse piston speeds would be slower (for longevity), which was something mentioned/calculated even in car road-tests back when.
Because they were designed primarily to be car engines, like all Chevy engines. Sure, truck use figured into the equation, but these had a big brief: to win on the drag strip and NASCAR, provide a smooth efficient big V8 for the family station wagon, and haul a load in a truck.
But GMC’s big V6 engine, designed strictly for trucks, was quite oversquare too. There’s nothing specifically that says truck engines should be undersquare. In fact, I can’t readily think of any American gas engines since the ’60s used in trucks that were undersquare except for the Ford 300 and Chevy 292 sixes, and that’s because they were stroker versions of smaller sixes used in passenger cars.
The only ting that kept these Chevy V8’s from revving even higher was their governors, which cut in at 4000 rpm, which is pretty high for continuous wide open throttle use. They were noisy!
Ah, I wasn’t sure if they were specific truck motors, with the sizes more or less coincidental to the cars.
I always associate heavy lugging work with long strokes, but that’s ofcourse not necessarily so. I once drove one of those rather silly 1.8 litre Mazda V6’s, and it had almost literally nothing at all till 3-4K revs, but I just looked it up, and, whilst oversquare, it’s about the same ratio as one of these V8’s, (though one sure wouldn’t fit it to a truck!).
The really big truck motors, though, like the Volvo one in Johannes’ post today, are still oversquare. Thinking of which, I’m sure a tip-truck of this size would have a much bigger output engine than this today, probably via turbo (and diesel).
The reason given for the undersquare dimensions of the GMC V-6 was slower piston speeds at a given r.p.m. and thus less wear than a comparable long stroke engine at the same r.p.m.. Nonetheless the GMC V-6’s were usually governed to relatively low r.p.m.’s for economy and durability, their flat torque curve not requiring a lot of engine speed to make good power. These engines also had tremendous reciprocating mass…..
The reason given for the undersquare dimensions of the GMC V-6 was slower piston speeds at a given r.p.m. and thus less wear than a comparable long stroke engine at the same r.p.m..
That and the better breathing because of room for bigger valves and ports are the two overwhelming reason for oversquare engines in general.
But undersquare engines have become quite common again. Almost all Honda fours are, as well as others. Turns out there are also advantages to undersquare engines too. And the disadvantages have been compensated for with things like balance shafts, four valve heads and variable valve timing.
Yes, and the valves were quite large on the V-6’s. In 1966 GMC came out with a redesigned cylinder head for the V-6 that had even larger ports and valves, along with matching intake and exhaust manifolds. V-6’s so equipped were referred to as ‘Magnums’, a year before Dodge starting calling their high performance engines by the same name.
The Ford 300 is closer to square.with a 4in bore and a 3.98in stroke.
The pictures are interesting. My intuition says that the biggest problem was probably not the load from up and down bouncing – that’s the way the pieces were designed to move to accommodate those forces. The big problem was probably fore aft and side loads, particularly braking, because you have some relatively small, dainty parts with the job of holding everything steady. There would seem to be a lot of leverage/torque working on those A arm bushings every time a really heavy truck hits the brakes, a force that is missing on the leaf sprung I beams. The changes listed in your factory materials suggest they were all made to keep stuff from moving around under stress.
Back in the 80s there was a 60-62 GMC grain truck still at work on my BIL’s farm. I got to drive it once and experience the big V6. I wish I had known to crawl under and see if it had this suspension setup. As you noted before, it may not have as it was less common on GMCs and that truck may have been heavy enough that it was not offered.
Thanks for another dive into this rabbit hole, and especially for finding one still out at work!
This is quite the find! Taking this geometry and upsizing it to work on the big trucks was a sound idea but the execution was certainly the pitfall.
Looking at this suspension made me wonder how much fun it would be to replace the ball joints on one of these.
In regards to the unknown arm on the steering column, might this be a replacement steering column? I don’t know enough about these to know if the columns from a smaller unit would work or not, but it makes me wonder if this column might have originally been in a three-speed half-ton and found a new life in this C80.
In regards to the unknown arm on the steering column, might this be a replacement steering column?
No; looks decidedly different. The arm is attached to a controller of some sort; almost certainly for trailer brakes.
What the heck is “improved front wheel piloting” as mentioned in the 1962 update?
In the usual context wheel “piloting” would be a reference to fit at the hub, insuring concentric operation. However, with the reference to reducing shock, that doesn’t make a lot of sense. Although no doubt keeping the wheels spinning round would naturally reduce shock.
Would the “shifter” on the steering column maybe be a throttle control for PTO situations?
Hand throttles were just simple cables to the dash, like a manual choke. This has a controller to it that really does look like a trailer brake controller. That’s my guess, and another commenter also agrees.
Fascinating stuff, Paul, thank you. And I (very sadly) think you’re correct with the general premise that GM had a nasty habit of releasing upgrades that were either half-baked, without enough field testing, or hampered in execution by the accounting department – or maybe a combination of the two.
Likely, the “shifter” on the steering column was a so-called trolley brake lever – essentially a valve which would apply trailer brakes independently of the truck’s service brakes. Many dump trucks were converted semi-trailer tractors and thus would have had that feature. Sometimes they were modified to apply and hold the service brake (like a very effective 4 wheel parking brake) while the truck was doing some stationary task, like operating a catch basi cleaner. At any rare, the .ever was associated with the air brake system.
Yup that lever is for applying the trailer air brakes independently of the truck’s brakes.
From the front wheel-end pictures, this hasn’t seen lubrication nor brake adjustment since Johnson’s presidency.
I’ll always have a fondness for Chevy trucks of this era. I associate them with my late father. I learned to drive straight shift in a ’61 Chevy Viking 50 on the farm. It was a wrestling match!
Fascinating. I wonder what the replacement parts supply is like not that it seems to be bothering this owner.
I’ve always wondered why GM discontinued the IFS on these big trucks, I’ve owned several of them and haven’t seen any breakage or failure issues. My best guess is that the accountants ended the design due to high cost of manufacture, and GM didn’t see dramatically higher sales volume due to the design as compared to the competition.
I’m sure it’s a combination of cost and some issues that arose with them in very demanding situations. Ultimately, the benefit was very modest at best, as the improvement in ride was pretty negligible. I suspect fleet owners gave some pretty convincing feedback too.
The mystery lever could very well be a hand brake. (for testing trailer brakes while pre tripping or old timers would try to independently modulate trailer brakes before the advent of ABS). Although I think there should be air lines coming in from the side and there should be glad hands somewhere on the rear plate. Its interesting to see the lack of the standardized yellow square parking brake that is common today on all air braked vehicles. My old gradall had the same horizontal slider switch as this truck that would hold the clutch on the floor while activating a hydraulic pump to remotely move the chassis around a jobsite. I think that would definatley active the pto. Lastly can you imagine trying to float gears on the trans with that old rusty rod digging in your palm? Ouch!
The air brake system was originally spec’d for trailer towing. The column located control operates trailer brakes alone.
The dash control is used to limit front axle braking under slippery road conditions.
The system doesn’t have an “air” parking brake at the the wheels; only the completely separate driveshaft located parking brake.
IMHO, with regard to longevity and ease of maintenance, this truck was spec’d with the best brake system of the available options. That’s probably one of the reasons it’s still on the job. With some other brake systems the cost of a brake overhaul has “retired” many trucks.
Postscript: I forgot to mention that this truck has either had a ’60-’61 grille swapped in, or it is a ’60-’61 with a newer hood. The ’62 grille had single headlamps.
Since trucks like this don’t exactly fly off the assembly line compared to passenger cars, perhaps it is factory built, just a between year transition unit? I can see it. A buyer of a truck like this in ’61-62 would most likely have not noticed or cared. I didn’t even notice it until you pointed it out.
The first (color) illustration of the suspension shows the torsion bars attached to the lower control arms. The second (b&w) illustration and the photo of the old truck show the torsion bars attached to the upper control arms. Perhaps the first illustration shows the lighter-duty version?
I agree the handle on the right is for operating trailer air brakes. Johnson bar is another nickname for the brake lever. Some would use this as a parking brake but it was not a safe thing to do. My dad used a bungee cord to hold it in place, another bad idea. Northwestern Gravel had a fleet of these and a common had bungee cords run between the doors to keep them shut. Dump trucks and garbage trucks lead tough lives. Looks like the truck itself is hydraulic brakes.
With a close look at the pictures showing inside of the front brake backing plates, cam-brake slack adjusters and chambers are visible.
Ditto the rear shot, cam-brake chambers are visible.
A complicated looking front suspension form what I see. If I had to work on the rebuild of one these in a Chevy C10 vs the I-Beam in a F-100 I’ll take the F-100 hands down as I can attest to it directly now.
Ditto! The twin-I Beam is delightfully simple and sturdy. I wonder why it took so long for someone to come up with it? It seems so obvious. This could have been a great solution for IFS back in the ’30s.
Unic came up with it in 1935:
My understanding is Ford adopted it to compete with GM’s pickup IFS without having to substantially redesign their chassis. Simplicity and durability were added bonuses.
Great series Paul. I had a half ton 60 GMC with the little truck version of this and combined with the coil rear springs it rode and drove well. The later 305E V6 in it could move anything but in typical GM fashion, the brakes were crap. A friend currently owns a flatbed 60 Chevy C60 with a 235 and the suspension seems to have held up ok. Don’t know how it will handle a D478 Toro Flow repower if we ever get around to it. As far as the twin I beam goes on the Fords NO THANK YOU! Absolute crap for on the road vocational use. Super rugged and simple yes but garbage on tires. great for ff road use sure but not for pavement. We had a pair of mid 80’s E350 vans at work with a 6.9 oil burner and could not keep tires on the things. By design the camber is constantly changing, throw in curvy mountain roads and your cost per mile heads right up. To keep the things somewhat straight you would be looking at replacing the springs about every three years so they wouldn’t sag into always negative camber. At least they don’t do the Dodge death wobble. I love old trucks but the twin I beam is the deal breaker for me with the Fords.
I beg to differ. My Twin Traction Beam in my ’83 Ranger DOES NOT wear out tires. Why? it was aligned by a shop that knows what its doing, not a local chain tire store that shall remain nameless. And ride height has to be perfect; if you have old, saggy springs, forget it, it will never align correctly, and it will wear tires. My truck drives like a dream, even with 31-10.50 tires, and does not wear tires.
The geometry of Ford’s ‘Twin-I-Beam’ is a disaster, even more so now as on the latest Fords so equipped the right beam is substantially shorter than the left! Camber changes with suspension deflection cause tire wear, as does the lateral scrubbing effect because the track also changes. As for the Dodge ‘Death Wobble’, you are right, Fords with ‘Twin-I-Beam’ front suspension do not exhibit the condition. However, the larger 4X4 Ford trucks certainly do!
I’ve heard complaints about those issues over the years, but it sure hasn’t played out on my old ’66. Of course I put very few miles on it.
Amen on TIB geometry, with the abuse of a tail dragging overload one relatively short trip will eat the steer tires alive.
All this Twin I Beam hate makes me glad my F-150 is a 4×2 aero body with A arms. That said our 93 Ranger had TIB and I never noticed any unusual tire wear so perhaps the lighter vehicle was easier on its tires.
My burning question about big GM IFS trucks is, would any truck shop in the early-mid ’60s actually been equipped to do an alignment on one?
A teeny bit from GM’s fall 1959 SAE paper “Design for a Better Ride,” with everything behind the decision to choose the IRS/torsion design as well as materials, manufacture, testing, etc. Lots of data comparisons are made vis-a-vis the 1959 Chevy trucks themselves: