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Different-size wheels can ruin differential

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Question — AutoNation sold me a 1997 Ford F-150 with 17-inch wheels and a 16-inch spare. I never knew this until I blew my front differential to bits. I was about 50 miles from the nearest town when I had to put on the spare, and I drove pretty slowly (no more than 40 mph) until the thing blew up.

I paid AutoNation a lot of money for a bumper-to-bumper warranty, only to be told, "You drove the thing on the wrong-size tires, you dope! Of course you're not covered!" So, who is wrong here? Is the warranty company too picky? Did AutoNation commit a major crime selling me a car with the wrong-size spare? Or am I just an idiot for not noticing? And if I can ever pay for the repair, should I buy a 17-inch wheel for a new spare tire? — Stuart

TOM: Well, to answer your last question first, Stuart: Yes. Using two different-size wheels on the driven wheels of a vehicle (the front wheels of your truck are driven in four-wheel-drive mode) will eventually ruin a differential. But you already learned that the hard way, Stu.

RAY: This is actually a tough one because each party can claim some guilt. A different-size wheel on the spare tire is the kind of detail lots of people would overlook. But since AutoNation sold you the car, and since it undoubtedly gave you some kind of warranty that stated or implied the vehicle was in good working condition and presumably contained all of the necessary parts with which to operate, I'd have to say that they should be held responsible.

TOM: And the warranty I'm talking about is the basic one that came with the purchase of the truck, not the additional warranty that's administered by a separate company.

RAY: AutoNation bills itself as a company that buys good-quality used cars. But part of its pitch is that it inspects the cars carefully, fixes any problems and then sells them to you as "guaranteed." Well, I would say this is a "problem" that should have been fixed before the truck was sold. It's not a common problem, so I can see how it might be overlooked, but it's AutoNation's job NOT to overlook it.

TOM: I don't think you can hold Ford responsible. When you order a new Ford with optional, larger wheels, you automatically get a spare that matches those wheels. So your 17-inchers were added after the truck left the factory — either by a dealer or a previous owner. And in that case, AutoNation would have the responsibility of correcting that problem before selling you the truck.

RAY: This is, of course, just our opinion. AutoNation might disagree. In fact, there might even be a warning in your owner's manual that tells you to check the size of your spare before using it. And if that's the case, be sure to rip that page out before going to small-claims court!

TOM: And that's where I'd go if AutoNation elects not to be nice guys and replace your differential AND your spare, or at least make a substantial contribution to their replacements. Differentials are expensive. I know. I've made many, many boat payments off of them! Good luck, Stuart.

To order Tom and Ray's pamphlet "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" send $3 (check or money order) and a stamped (55 cents), self-addressed, No. 10 envelope to Ruin, P.O. Box 536475, Orlando, FL 32853-6475.

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