There are some boots that don't come in a shoe box and aren't worn on your feet. They are called axle or CV boots, and they can be important parts for many vehicles.
That CV stands for constant velocity. CV axles are mainly used in front-wheel drive and all-wheel drive vehicles. They're also used in some rear-wheel drive vehicles with independent suspensions. They have two CV joints, one inner and one outer, placed between the axle and the drive wheels. That way the vehicle's engine power can drive the wheels, no matter what angle they are. They also adjust for the different speeds wheels turn as they go around corners.
Because roads are full of all sorts of hazards (dirt, oil, water, grime), these CV joints need to be protected. They also have grease in them to keep the bearings moving smoothly. That's the job of the rubber boots that are supposed to keep that debris out. These CV or axle boots are made of rubber or plastic and usually last a long time without any problem. But sometimes they fail, either from being hit by debris or age causing the rubber or plastic to deteriorate. That can allow the grease to leak out of the joint and the moisture to get in. And that's where the trouble is.
So it's important to have a vehicle's CV boots checked periodically, especially when they begin to have more than 100,000 miles/160,000 kilometers on them. A technician inspects them for tears or cracks. Sometimes if the problems are found early enough, the boots can be replaced and the joints can be re-packed with grease.
But sometimes the CV joint can wear out even though the boot is intact. When the CV joint fails, you might hear a grinding, humming or clicking noise and feel vibration.
Some of these can be difficult to access for service, so many service advisors will recommend replacing the joints and boots at the same time. Just remember, new CV boots won't make a fashion statement, but they will keep your vehicle going down the road for years to come.
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