I live in Spring Hill, Fla., where most of us drivers are over 70 (they sometimes call this God's Waiting Room!). I've enjoyed reading your responses to other people's problems for years, and now it's my turn. My 1989 Buick Century (blue, with sun-and-car-wash-damaged paint) has 160,000 miles. This week, after the car has been running for 30 miles or so, it doesn't seem to downshift very well. When I slow down, it shudders and has twice stalled out. I checked the transmission fluid and added some, but it still did it the next day. What's happening here, and what should I expect to pay to fix it? -- Bill

Tom: I think your torque converter clutch is on the fritz, Bill.

Ray: Don't confuse the guy by using technical jargon, Tommy.

Tom: What? Torque converter clutch?

Ray: No. "Fritz!"

Tom: Oh. Let me explain, Bill. Modern automatic transmissions have a device called a lock-up torque converter, which locks the transmission into high gear whenever you exceed 35 mph or so (which we know is rare for you guys in Spring Hill, Fla!).

Ray: Why does it do this? To improve fuel efficiency. Automatic transmissions use a fluid connection, and are always "slipping." The fact that they can slip makes it possible for you to stop the car without taking the transmission out of gear.

Tom: If you stopped a manual-transmission car without taking it out of gear, it would do what? Stall, right?

Ray: But that slipping, because it's less efficient than a hard, mechanical connection, does cost you some gas mileage. So the lock-up torque converter locks the automatic transmission into high gear at speeds over 35 mph, as if the transmission were manual. That gives you the best of both worlds. And it sounds like your torque converter clutch isn't disengaging. It's as if you were driving a manual-transmission car, got off the highway, and tried to come to a stop with the car still in fourth gear. What would happen? The car would buck and eventually stall. And that's exactly what's happening to your car.

Tom: So, normally you would fix this by replacing the torque converter, which requires taking apart the transmission. But since your car has 160,000 miles on it, and its future is even more in doubt than yours, Bill, you might consider just unplugging the torque converter clutch, which does not require opening up the transmission, and takes only a few minutes. Your mileage may get a tiny bit worse, but you won't notice any other difference in performance.

Ray: Some mechanics may try to convince you that damage can eventually be done to the transmission by just unplugging the torque converter rather than fixing it, but we haven't seen any proof that that's true. And besides, after racking up 160,000 miles on this car, you've earned the right to do whatever you want, Bill.

Auto repairs can be costly! Save money by ordering Tom and Ray's pamphlet "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1997 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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