Car News:  Oversteer

Pontiac's Rope Drive: The Flexible Driveshaft That Will Bend Your Mind

RELATED READING
See all Pontiac any articles
RESEARCH BY MAKE
Toyota cars, trucks and SUVs Ford cars, trucks and SUVs Honda cars, trucks and SUVs Chevrolet cars, trucks and SUVs Jeep cars, trucks and SUVs Nissan cars, trucks and SUVs BMW cars, trucks and SUVs Mercedes-Benz cars, trucks and SUVs Volkswagen cars, trucks and SUVs
Acura cars, trucks and SUVs Alfa Romeo cars, trucks and SUVs AMC cars, trucks and SUVs Aston Martin cars, trucks and SUVs Audi cars, trucks and SUVs Bentley cars, trucks and SUVs BMW cars, trucks and SUVs Bugatti cars, trucks and SUVs Buick cars, trucks and SUVs Cadillac cars, trucks and SUVs Chevrolet cars, trucks and SUVs Chrysler cars, trucks and SUVs Daewoo cars, trucks and SUVs Datsun cars, trucks and SUVs DeLorean cars, trucks and SUVs Dodge cars, trucks and SUVs Eagle cars, trucks and SUVs Ferrari cars, trucks and SUVs FIAT cars, trucks and SUVs Fisker cars, trucks and SUVs Ford cars, trucks and SUVs Freightliner cars, trucks and SUVs Genesis cars, trucks and SUVs Geo cars, trucks and SUVs GMC cars, trucks and SUVs Honda cars, trucks and SUVs HUMMER cars, trucks and SUVs Hyundai cars, trucks and SUVs INFINITI cars, trucks and SUVs Isuzu cars, trucks and SUVs Jaguar cars, trucks and SUVs Jeep cars, trucks and SUVs Kia cars, trucks and SUVs Lamborghini cars, trucks and SUVs Land Rover cars, trucks and SUVs Lexus cars, trucks and SUVs Lincoln cars, trucks and SUVs Lotus cars, trucks and SUVs Maserati cars, trucks and SUVs Maybach cars, trucks and SUVs Mazda cars, trucks and SUVs McLaren cars, trucks and SUVs Mercedes-Benz cars, trucks and SUVs Mercury cars, trucks and SUVs MINI cars, trucks and SUVs Mitsubishi cars, trucks and SUVs Nissan cars, trucks and SUVs Oldsmobile cars, trucks and SUVs Plymouth cars, trucks and SUVs Pontiac cars, trucks and SUVs Porsche cars, trucks and SUVs RAM cars, trucks and SUVs Rolls-Royce cars, trucks and SUVs Saab cars, trucks and SUVs Saturn cars, trucks and SUVs Scion cars, trucks and SUVs smart cars, trucks and SUVs SRT cars, trucks and SUVs Subaru cars, trucks and SUVs Suzuki cars, trucks and SUVs Tesla cars, trucks and SUVs Toyota cars, trucks and SUVs Volkswagen cars, trucks and SUVs Volvo cars, trucks and SUVs Yugo cars, trucks and SUVs
RESEARCH BY STYLE
AWD/4WD
Commercial
Convertible
Coupe
Hatchback
Hybrid/Electric
Luxury
Sedan
SUV/Crossover
Truck
Van/Minivan
Wagon
ADDITIONAL MODEL INFORMATION

author photo by Aaron Gold May 2017

I love creative engineering, and I love it all the more when it comes from an unlikely source. That's what makes the Pontiac rope drive of 1961 such a cool thing: Not only is it bizarre as all get-out, but it came from General Motors at a time when they were the bastion of conservative management.

The 1961 Pontiac Tempest was a font of new ideas. The engine was a 3.2-liter 4-cylinder that looked like what it was: A 389 V8 with the right cylinder bank lopped off. (It was designed to be built on the same assembly line as the 389.) Out back, it had an independent swing-arm suspension surrounding a rear-mounted transaxle. And connecting them was the rope drive of which we speak.

Instead of a traditional drive shaft, the Tempest used a thin steel shaft concealed inside a torque tube -- "no thicker than a man's thumb and curved like a swaybacked horse," explained the September 1960 issue of Popular Science magazine. The Tempest's engine was tilted upwards, and the driveshaft shaft deflected 3 inches between the center and the ends. This had the happy effect of reducing the size of the transmission tunnel (already decreased by the rear-mounted transmission) and eliminating the need for universal joints.

But these were just added benefits. The real reason for the swaybacked shaft had to do with vibration, a major problem with the big four, which lacked a balance shaft and already had special motor mounts to absorb the vertical shaking. PopSci explains the rope drive's role: "With a straight shaft, the rotating speed at which its natural frequency might cause vibration would fall within the shaft's normal operating speed," the mag reported. "Curving it raises the natural vibration frequency above the highest speed at which the shaft must turn." (Ah, physics.)

Another nifty detail about the rope drive was how spindly the driveshaft was -- it wasn't really a rope, but at five-eighths of an inch in diameter (three-quarters of an inch for manual-transmission cars), it looked pretty darn close. Typical prop shafts of the era were on the order of 2.25 inches or more. PopSci explained that traditional drive shafts must carry the heavier torque loads as multiplied by the transmission; the torque load between engine and transmission is significantly lighter, hence the ability to use a thinner, lighter shaft.

One might wonder how a tight-collared company like General Motors would allow such engineering extravagance from one upstart division. The answer: Pontiac's chief engineer at the time was John Z. DeLorean, a man who was always looking to inject new thinking into the corporate hive-mind that was GM. (I highly recommend "On A Clear Day You Can See General Motors," DeLorean's authorized-then-unauthorized biography, which goes into entertaining detail about how the sharply dressed John Z continually confounded the suits at GM.) John Z was responsible for a long list of engineering advances, including the "wide-track" '59 Pontiacs, the division's overhead-cam straight six, concealed wipers, plastic "Endura" bumpers and antennas embedded in windshield glass. He developed the GTO and the "personal luxury" Grand Prix, and he was a driving force behind the Chevrolet Vega. And, of course, we all know the gull-wing-door sports car that bears his name. (Shame about that whole cocaine thing.)

The Tempest won accolades from the press: Motor Trend named it their Car of the Year for 1961, and Road & Track was ebullient in their praise. It was one of the most innovative American cars of the era, and its split powertrain and independent rear end gave it outstanding balance. But the car had its problems: Tricky at-the-limit handling (including a snap-oversteer problem) and harshness from the big 4-cylinder made it less than endearing to the general public.

Such radical engineering at GM was, as the British would say, "Not the done thing, petal," and in 1964 the Tempest was enlarged to share its platform with other GM intermediates. Of course, by then, DeLorean had moved on to other things: He was figuring out how to bend GM's rules and get a 389 (6.4-liter) V8 into the new Tempest, resulting in the legendary Pontiac GTO.

And what of the rope drive? So far as I can tell, it hasn't been used in another GM product since the Tempest (or any mass-produced car sold in the U.S.; please tell me in the comments if I'm wrong). But the split-powertrain idea would be revived for the 1997 C5 Corvette, which has retained the rear-mounted transaxle ever since.

Photo: Lars-Goran Lindgren

MORE FROM OVERSTEER:
This Never-Driven Porsche 918 Spyder Is on Autotrader for $1.8 Million
The Land Rover Discovery's Headrests Have a Cool Trick
I'm Swapping an LS V8 Into My 248,000-Mile Porsche 911

This image is a stock photo and is not an exact representation of any vehicle offered for sale. Advertised vehicles of this model may have styling, trim levels, colors and optional equipment that differ from the stock photo.
Pontiac's Rope Drive: The Flexible Driveshaft That Will Bend Your Mind - Autotrader