This Old Chevy Owner’s Manual Warns Of Hilariously Dire Consequences Of Tire Overinflation (Plus A Reminder That Chevy Sorta Had A CVT In The 1950s)


For a complicated chain of reasons I don’t really want to get into right now, and because a promise made under duress to the American Council of Churches prevents me, I was looking through the owner’s manual of a 1957 Chevrolet. As far as old cars go, a ’57 Chevy is a little vanilla for my perverse tastes, but I did find something in this manual that was genuinely surprising. It’s from the part about tire inflation. There’s also a few other unexpected tidbits in here that I need to share with you, because I literally have no one else who will listen to me right now. So get ready.

First, let me show you what this 1957 owner’s manual has to say about tire inflation:

Okay, let’s see here: under-inflated tires are bad, could cause blowouts, okay, got it, and of course proper inflation is great, good everything, better mileage, gets you a place among The Elect, I get it, and now overinflation, lets’s see, poor traction, blah blah blah, and wait. Bruises? Fabric breaks?

Bruises? What, exactly, is Chevy saying here? Will GM send goons to work you over if your tires are overinflated? Or is this just a reminder that cars of the 1950s were full of hard, unforgiving surfaces and pointy, jabby things that would smack painfully into your tender flesh as you bounced down the road on tires as tight as snare drums, skittering all over the vast expanses of vinyl bench seat until you impacted, hard, into a chrome gargoyle installed on the dash?

Honestly, this is the first time I’ve ever seen a warning for bruises in a car owner’s manual.

There’s more interesting details, too! Like this–look at the bold safety hint:

See that? What’s interesting about that is that it’s sort of predicting the coming of hazard lights about a decade before they were required on cars (that would be 1968, though they had been developed earlier). The use case described here–having a flashing light on while changing a flat–is precisely the sort of thing hazard lights were designed to do.

What else do we have here? Oh, look at this:

This is something I didn’t think was in use in the 1950s–essentially, this is a front/back fader system for the radio, except it’s less of a “fader” and more of an on/off switch because that’s exactly what it is. You could turn the rear speaker on or off in these Chevys, and while it wasn’t stereo (the rear speaker was just carrying the same mono signal as the one in front) it’s interesting that you could at least choose to pump the music to the back or not.

Most interesting, though, I think is the realization (at least for me, and I suspect at least a few of you devastatingly attractive readers) is that GM had a continuously variable transmission (CVT) way back in the 1950s. Well, a sort-of CVT.

The reason I find this surprising is that we tend to equate CVTs with modern cars, especially hybrids and very efficient cars. And while the conventional sort of belt-driven CVT (there’s also gear-based ones) was developed by the Dutch company DAF and brought to market in 1958, making it the first mass-market CVT, the GM system, called Turboglide, is pretty close to being a CVT. Maybe not exactly, but the effect of it is pretty similar.

In the manual I saw, I know a Turboglide was involved because well, it said so, and this unusual gear selection:

That HR range, for “Hill Retarder” has an unfortunate name not just because of the other, pejorative associations of the non-hill word there, but also because people thought it meant “High Range” which, of course, is the exact opposite of what it’s for. GM changed the name to GR for “Grade Retarder” the next year to avoid this.

But let’s talk about the Turboglide for a moment here, specifically looking at it in the context of a sort-of CVT. GM’s automatic transmissions of the 1950s were generally pretty primitive, some being basic two-speed units that provided easy driving but were pretty awful for efficiency. I don’t think that was the reason for the Turboglide, as this was the era of cheap gas and a severe dearth of fucks given, but smoothness as a concept was a big deal, and the Turboglide dished that out generously.

The Turboglide was a torque converter-type of automatic transmission like their previous ones, but this one had three separate turbines in the torque converter that worked concurrently to drive the car.

That means the transmission wasn’t ever really shifting from one gear to another, but rather adding or removing input from the turbine couplings into the mix of ratios used to move the car. An old Chevrolet manual analogizes it with a triple-person bicycle:

So, imagine that you’re starting on your bike trip, so you have all three cyclists pedaling. The one at the rear, with the smallest gear and the most torque, is doing most of the work. The high gear cyclist is barely able to do anything at this point. As you get going, the middle one is handling the most, with some input from the low and high cyclists, with low tapering off as speed increases, until it’s just middle and front, then just the front one at high speeds.

The Turboglide works much the same way, sort of “blending” the three gear ratios as the car drives. The result is a lot like a CVT in that the engine revs stay pretty consistent as the car changes speed, and there’s not really perceptible gear changes.

Is it a real CVT? Not really, as there are still three gear ratios, but in the way it drives and feels, it’s very CVT-like. From what I’ve been reading, Turboglides drove a bit strangely (so do many CVTs, if you ask me) and had their share of problems, eventually being discontinued in 1961. Still, this is a fascinating bit of engineering that I think tends to get overlooked, especially considering how common real CVTs are now.

I’ve not found any mention how much they contribute to bruising, though.

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30 Responses

  1. My grandparents had a new’57 Belair with the 283 power pack and Turboglide. My uncle was 16 years old and has long extolled its performance, claiming to have beaten a Corvette in a street race. HIs dad was very happy with the car at first but couldn’t understand why the rear tires were wearing out so fast. He also started having trouble with the Turboglide shortly after purchase. The trans was replaced twice in five years of ownership. Many years later Unk told me that he heard that since there were no gears in a Turboglide, you could shift into reverse while going down the road at 70 mph and it wouldn’t hurt the trans at all. So, being the brilliant 16 y/o he was, he tried it. He said it just made a loud roaring bellow as the car slowed down but it didn’t hurt a thing. What he failed to mention is that it went back to the dealer for the first new trans shortly after that. I don’t know about the second trans, but I suspect Unk had something to do with it. After he left home for the Marine Corps the car problems seemed to just stop.
    Maybe I shouldn’t be so hard on Unk because this was the first year of a new trans and there may have been problems right from the factory. However, he had earned quite a reputation for his driving around our small town, particularly with some guys who drove blue cars with red lights on top. That was ironic, as he later became a State Trooper and spent his work days driving one of those himself.

  2. You accidentally called it “Torqueflight” towards the bottom.

    Never knew this transmission existed.

    I’m thinking the terms on the tire caption indicate damage to the tire. They had all sorts of weird terminology back then, “Hill-Retarder” being an awesome example. Ya get the feeling, sometimes, that they were trying to sound more advanced or superior, without being too condescending.

    1. Engineers do that a lot. Lol I think the bruising was a term used to refer to singular flat spots on tires from chunks separating from the tire. Kind of like cupping but just a single chunk. Remember tire quality was not so good back then. As a matter of fact just about every car sold came with a jack and a full sized spare. And people also knew how to plug their own tire leaks.

      1. Torch, as a fellow graphic design and font aficionado i can’t believe you cannot love, love, love how they treated the word “Guide” on the cover of that manual. It deserves a column unto itself.

  3. In my perfect world the three person bike is a fixie, so the riders that think they’re getting to slack off most of the time you’re at cruising speed instead have to devise some strategy for dealing with pedals moving faster than they can.

    The rear seat would basically just be for punishment.

    1. Doesn’t even have to be a fixie. On every tandem I’ve ridden both sets of pedals are directly attached by the chain so everyone has to keep pedaling no matter what. There’s no per-crank freewheeling (although apparently that’s a thing on ebikes now, so maybe it could be).

  4. Why didn’t they just use “L” for low gear like everyone else? I know they say it’s not really low range, but if it amounts to the same thing, why confuse drivers by changing naming conventions?

    It’s also interesting that they had already moved reverse to between park and neutral, which I thought happened later. The early Powerglides and Dynaflows were P-N-D-L-R.

    1. Generations later Chevrolet did the exact flip of it in the pre-facelift Bolt EV, labeling the max-regen/one-pedal-drivable mode L on the shifter even though there’s no reason you can’t use it on the open highway.

    2. It actually had a special clutch (called the “grade clutch”) that would release the drive clutches and ground the ring gear of one of the planetary sets. This would spin the first turbine (and therefore the engine) to give some braking on a steep grade. Otherwise, the first two turbines would freewheel because of their overrunning clutches and you’d get no engine braking at all.

      TL, DR: If you selected that range at a stop and hit the gas, the car wouldn’t move. It would only provide engine braking. So it really wasn’t a low gear at all.

  5. I am not in any way a fan of Chevrolet or their products BUT they seem to have the best explainers for how their tech works. That bike analogy is good and that one old video on YouTube about differentials is great too.

  6. There is a great book from SAE Press called “Changing Gears: The Development of the Automotive Transmission”, by Philip G Gott. It’s all about the development of the automatic transmission from 1900 up to the mid 1980s. It covers all the weird and wonderful attempts to make a reliable automatic.

  7. My mother had a 1966 Mercury Cyclone GT. Yes, I’m very proud. It had a four flasher that activated by flipping a switch in the glove box and then hitting the turn signal, either way. I can’t swear if this was original or after market as she got the car in 1969, but it was there.

  8. As my dad grew increasingly annoyed by the popular music of the mid-1960s — and by my brother’s taste in music — he thought he’d found the solution in a rear-seat speaker when he bought our new ’67 Ford. He had it dealer installed with the control nicely integrated into the standard radio knobs and the speaker mounted beneath the rear parcel shelf. Mono of course. By this time, though, my brother decided he was too old to go on vacations or other road trips with the family so the effort was more or less wasted. It probably didn’t cost more than about $15 so no great loss.

  9. Ah the Turboglide! My Great Grandpa was head of the transmission division of GM at the time, and I remember my grandfather telling me of how big of a nightmare it was to get these transmissions launched, and then working properly. They only lasted a few years until they were replaced with the legendary (and long lasting) turbo hydramatic transmissions. I’m glad you wrote this up, I’ve been looking for more information on these oddball transmissions for years!

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