Clutch Performance

Dyer Consequences

I’m driving up a hill in a new Dodge Dart when the revs start climbing, independent of the car’s speed. “Stupid CVTs,” I think, because anguished endless revving is a total CVT move. But my moment of consternation quickly gives way to confusion when I remember that this particular Dart doesn’t have a continuously variable transmission. It has a six-speed manual, the behavior of which indicates that the clutch is on its way out in a hurry. I move over to the breakdown lane, and within a mile the Dart is immobile, its clutch no longer on speaking terms with its flywheel. And with that, I’m tossed headlong into an increasingly rare circumstance: the roadside breakdown.

New cars, it seems, don’t break down. I’ve driven hundreds of new cars over the past decade and none has suffered a catastrophic failure, despite some serious abuse on my part. I once accidentally tried to shift a Chevy Camaro SS into reverse at 140 mph on the Bonneville Salt Flats (fifth gear is next to reverse and I had some adrenaline flowing), and that brain fart proved a mere footnote in a trouble-free 1600-mile trip. I put 62,000 miles on my Mitsubishi Outlander and nothing went wrong. My AAA membership lapsed. The local tow-truck jockeys remained strangers.

This wasn’t always the case, even with relatively new cars. Before the advent of cell phones, almost everyone with a driver’s license knew the shame of trudging up a stranger’s steps to ask to use the phone. The breakdown procedure usually involved a rousing game of, “Which of these houses looks least murder-y?”
By the 1980s, cars were getting better but still weren’t entirely trustworthy. You had to be prepared to drive home by moonlight when your alternator crapped out or know that your four-wheel-drive Jeep Cherokee could limp home as a front-wheel-drive Jeep Cherokee if the rear driveshaft let go. (Neither of those, by the way, are hypothetical examples.) By 2000, you could expect a new car to be fairly bulletproof. Now, 100,000 miles just means you’re ready for some new spark plugs. I can’t even remember the last time I got a flat tire, let alone an all-hands-on-deck mechanical emergency.

Which brings me back to the Dart. The day of the clutchtastrophe, Chrysler flew in Rob Benson, senior manager of manual-transmission, four-wheel-drive, and driveline engineering, to go full CSI on the wounded Dodge. The question was whether this was death by natural causes or a premeditated clutchicide.
Here I should point out that I’m seldom the first person to drive a given vehicle, and there’s no telling what hijinks lay in the Dart’s history (like, say, trying to grab reverse at 140 mph on the Bonneville Salt Flats). The car in question had 2300 miles before I grabbed the keys, and there’s a strong possibility that those were not easy miles. By which I mean, there’s a strong possibility that someone used this Dart to teach a manatee to drive a stick shift.

“At some point, the clutch was heated to the point that there was bluing on the pressure plate and flywheel,” Benson tells me a few days later. “When you heat it to that level, the binding agents lose their ability to hold, and you lower the burst speed.” The burst speed is exactly what it sounds like, and the Dart’s clutch is rated to 13,000 rpm (double the engine’s 6500-rpm redline) before it goes kablooey. Which means that you could be the kind of moron who selects first gear and releases the clutch while coasting toward a red light at 60 mph and the clutch would still hold together even though you now have it spinning toward Formula 1 rpm levels. But if you spin a clutch to ludicrous speed after also overheating it, you could end up with the time bomb of partially burst clutch — it will hang in there for a while before the friction material separates in a major way. I drove the Dart sixty highway miles before the clutch gave up, so that diagnosis would fit.