What is a "half shaft"?

Dear Car Talk

Dear Car Talk | Dec 01, 1989

Dear Tom and Ray:

What is a "half shaft" in a 1984 Ford Tempo, and what makes it give out?

TOM: The "half shaft" is what you get from the dealer when your car is still under warranty. Once the warranty expires, Barbara, you get the complete shaft.

RAY: We're kidding Barbara. Front wheel drive cars like your Tempo have two axles in the front. They run from the transaxle in the middle of the car to the right and left front wheels. These axles are called "half shafts," because each of them spans half the width of the car.

TOM: The shafts themselves don't wear out. What usually fail are the Constant Velocity (CV) joints on either end of these axles. CVs are intricate ball and socket joints which are protected by rubber "boots." Often these boots rip, the grease inside gets thrown out, the CV joint disintegrates, and you end up getting the half shaft.

RAY: The reason you replace the entire shaft instead of just the CV joint has to do with the cost of labor. In many cases, rebuilding the shaft with new CV joints turns out to be more expensive than simply replacing the whole thing.

TOM: The best way to avoid getting the shaft in the future, by the way, is to have your mechanic inspect your CV boots every time you go in for service.

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