Click and Clack: Saving half a transmission at what cost?
05/24/2014 6:41 AM
05/24/2014 6:41 AM
Dear Tom and Ray:
A friend in high school back in the early ’70s would occasionally borrow his dad’s Ford Pinto to cruise us around. On odd-numbered days, he could use only first and third gears, and on even-numbered days, he could use only second and fourth. His dad was adamant that this would double the life of the transmission by using only half of it at any given time. My immediate question is: Do you guys think this is a sound method for increasing the life of a transmission, or was the boy’s father a bit too obsessive? And second, would anybody want to own a ’73 lime-green Pinto for that long anyway? – David
Ray: Your friend’s father was absolutely right. By using each gear only half as much, he was extending the life of the synchronizers on those gears and delaying a transmission rebuild.
Tom: But he was halving the lives of his clutches. Well, maybe not halving, but he was shortening the lives of his clutches considerably. So this was a bad trade-off.
Ray: When you start out in second gear, you have to use more gas and release the clutch pedal more slowly to get the car moving without stalling it.
Tom: And all that time when you’re revving the engine and slowly releasing the clutch pedal, you’re essentially sanding down your clutch disc. The clutch uses friction to connect the engine to the wheels. When you wear off the friction surface and make it smooth, the clutch is done for. Kaput.
Ray: Plus, whenever he was driving in too high a gear (every time he shifted to fourth when he should have been in third), he was lugging his engine. That builds up carbon, causes the engine to run hot and generally shortens the engine’s life.
Tom: And he’s doing all this presumably to extend the life of the transmission, even though transmissions are designed to last the life of the car (and often do).
Ray: Clutches, on the other hand, almost always wear out during the useful life of the car (generally between 75,000 to 100,000 miles, depending on how they’re used). So he was preventing a repair he might never need while shortening the life of the engine, and adding an extra clutch job or two to his bill.
Tom: Maybe he added more than one or two. It depends how long he suffered with this lime-green Pinto. He sounds like the kind of guy who likes to keep his cars a long time. So maybe he’s still driving it now? On its fourth engine and 41st clutch.