Dear Tom and Ray:

My question does not deal with car repair or maintenance. The vast majority of new cars today are front-wheel drive. Why doesn't any manufacturer make a full-size front-wheel-drive pickup truck? You can buy rear-wheel drive or four-wheel drive, but not front-wheel drive. Wouldn't a truck with front-wheel drive have really good traction? - JerryRAY: Good question, Jerry. The reason there aren't big, front-wheel-drive pickups has to do with balance. A vehicle handles best when its weight is distributed more or less evenly between the front and back.

TOM: Pickup trucks are out of balance to begin with. Even with rear-wheel drive, the rear end of a pickup truck is much lighter than the front end. Think about it: In the front you have the engine, the transmission, the gun racks and the entire cab compartment. In the back, you have what? The differential and a bunch of empty space.

RAY: So if you move the differential up front too, you create an even greater imbalance. You make the back end that much more likely to slide out on corners, and you make the rear brakes that much more prone to lock up (you may have noticed that some pickups now come equipped with rear anti-lock brakes for that very reason).

TOM: So unless you're going to radically redesign the pickup truck - like put the cab in the back - rear-wheel drive is the best way to go.

Dear Tom and Ray:

I got myself an '88 Chevy Astro Van. Among its options is a "limited slip differential." To a layman like me, that means that when one of the driven wheels starts slipping in mud or snow, the power transfers to the other wheel to keep me from getting stuck. The problem is my truck doesn't seem to do that. Is my understanding of limited slip differential that limited? Or if it's broken, how can I prove it to the dealer? - Martin

RAY: First of all, Martin, your understanding is not limited at all. Limited slip differential does exactly what you say it does. It automatically transfers power from the slipping wheel to the wheel that's on terra firma.

TOM: And yours may, in fact, be broken. Keep in mind, however, that if both of the rear wheels are on mud or snow, limited slip can't help you at all.

RAY: If your warranty is of limited duration, and your dealer is expressing limited interest in your problem until the warranty runs out, it should be pretty easy to demonstrate for the record that it doesn't work.

TOM: Next time you drive into the dealership's service area, bring something slippery to put under the driven wheel. We prefer extra-virgin olive oil. If the limited slip works, when you step on the gas, the power will be instantly transferred to the other wheel, and the van will screech away - probably right through the plateglass window and into the customer waiting area. If the limited slip doesn't work, the wheel will spin, and the dealer will be convinced. Good luck, Martin.

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