CV Joint Smarts

Learn about flexible constant velocity (CV) joints in this quick article.

CV JointCar makers use highly flexible constant velocity (CV) joints on front wheel drive (FWD) vehicles. The joints transfer torque to the front wheels and provide and allow for a much tighter turn radius than the older-style U-joints. But CV joints are far more complicated than U-joints and require regular inspections. Their useful life depends entirely on the integrity of the protective pleated rubber boot. Because once that boot develops cracks and starts leaking grease, the joint can self destruct in a matter of weeks. This photo shows a joint that was destroyed by water and road grit.

The outer joint (the one closest to the wheel) usually fails first because it flexes more in turns. Those are the joints you should check first. Just turn the wheels all the way to one side and peek behind the wheel with a flashlight. If you see any cracks in the boot or fresh grease, you have to make a quick decision—install a new boot or replace the entire axle with a rebuilt unit. Shops prefer to replace the entire axle with a rebuilt unit. That usually runs about $400 per axle for parts and labor. But if you catch the problem early and do the work yourself, you can save a lot of money. A new outer CV boot kit (boot, grease and new clamps) costs about $15 at any auto parts store. You’ll also need to buy (or rent) a special boot clamp pliers (like these from our affiliate Lisle 30800 CV Boot Clamp Pliers). And you’ll need a good shop manual. The job takes about four hours.

Whether you do the work yourself or take it to a shop, the important point to remember is that you cannot keep driving with a damaged CV boot. I’ve seen the damage caused when a worn CV joint flies apart. The spinning axle can destroy expensive suspension components, turning a $400 job into one that can costs upward of $1,500.

— Rick Muscoplat, Automotive Editor

For other DIY Auto Repair projects, visit our Auto Repair section.

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