Dear Tom and Ray:

We recently contacted the local Aamco transmission shop about servicing our 1992 Chevy Blazer's automatic transmission, which is working just fine. The vehicle has almost 100,000 miles of mostly highway driving. The Aamco man said that it should have been serviced every 25,000 miles and that it would now have scale deposits in the transmission and that doing the service now would cause problems. He said that it were his car, he would now do nothing to the transmission. We admit we've been negligent in letting it go this long, but is this guy right? It doesn't make sense to us. -- David and Patty

Tom: It doesn't make sense to us, either, guys. First of all, the recommended service interval for this transmission is 100,000 miles. So you're right on time. You haven't been negligent at all.

Ray: And I've never seen a recommendation from Chevy that calls for transmission service every 25,000 miles under normal conditions. That may be this particular Aamco shop's recommendation, because they'll make four times as much money if you do it that often. But I think the guy's wrong on that account.

Tom: This guy is also perpetuating the myth that "disturbing" an older transmission will somehow cause irreversible problems (this is also known as the "let sleeping transmissions lie" theory). This myth is based on the belief that the transmission has gotten used to its old, dirty fluid. And if you drain out that loving, old, comfortable, familiar fluid and introduce new, clean, uncaring, unfamiliar fluid, the transmission will be upset and won't remember how to work right. This, of course, is complete horse-droppings. A transmission fluid and filter change is never harmful, no matter how many zillions of miles you have on the car or how many fish scales you have in there.

Ray: Scale deposits, not fish scales.

Tom: Whatever. David and Patty, you should go to another mechanic and tell him you are coming in for your 100,000-mile transmission service. And don't worry about a thing.

Changing your oil regularly is the cheapest insurance you can buy for your car, but how often should you change it? Find out 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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