The constant velocity universal joints in front-drive axle shafts normally last a long time, but don't wait for a clicking noise on turns (indicating a bad outer joint) or an axle shaft hum. Inspect the CV joint boots whenever you're underneath, and if you find a small cut without a sign of lubricant leakage, clean the rubber and seal the wound with a dab of silicone RTV. If there's a large gash in the boot and evidence of grease leakage, but apparently no real damage, remove the boot and inspect it. You should be able to clean out any grease that shows only surface contamination with road film and moisture, repack with fresh grease (use specified CV joint grease) and install a split boot kit all without removing the axle shaft.

We're wary of being able to properly clean a CV joint without removing it from the vehicle and using solvent and a brush to get out the last bit of dried-out grease and mud. But if you're confident there's no contamination, it may be possible to avoid this step. The split boots have been improved recently and with careful installation, may last a couple of years.

If the grease leakage is extensive and the first hums or clicks have been heard, check a repair manual. You may find it's possible to take out the shaft and replace the innards of the joint without special tools. Or buy a factory rebuilt shaft from an auto parts store for the same price as a pair of CV joint kits. Unless the failure of one joint is premature, a complete shaft assembly is a sound investment.