CV Joints: What Are They?
February 29th, 2016
Many of the vehicles on the road today are front-wheel-drive; for FWD vehicles, the standard way to get torque from the car’s transmission to the front wheels is via CV (constant-velocity) joints.
Many of the vehicles on the road today are front-wheel-drive; for FWD vehicles, the standard way to get torque from the car’s transmission to the front wheels is via CV (constant-velocity) joints. Rear-wheel-drive vehicles use a U-joint at the front and rear of the driveshaft, but a conventional U-joint can’t accommodate as much movement as a can.
These joints are at the end of half-length axles, and transfer torque to the drive wheels while still allowing for steering and the up-and-down motion of the suspension. The inner and outer joints are packed in a special grease, then sealed with a rubber or plastic bellows-shaped boot that’s held in place with two clamps.
CV joints were more prone to failure in the 80s and 90s, but today many cars with over 200,000 miles still have the original CV joints in place. That doesn’t mean they’re foolproof, however!
The most common problem with a CV joint is when the boot itself starts to crack or degrade. When this happens, moisture and grit can enter the sealed unit and the grease begins to escape and leak. These are signs that this fairly common auto repair is coming up:
· Leaks of grease by the front wheels
· Front wheels are spattered with grease along the inside or outside of the rim
· Clicking, ratcheting or popping sound, especially while negotiating a tight turn or a U-turn. The sound will be louder while turning in one direction than the other.
· Shudder or side-to-side shake while accelerating. This can also be a sign of a failing motor mount, which is another fairly common problem with FWD vehicles.
If left too long, a CV joint can even completely fail and come loose while driving. If this happens, the half-axle can flop around and damage other nearby parts such as the power steering pump, oil pan or transmission, turning a fairly simple auto repair into a really expensive one. It can even drop down and dig into the pavement, vaulting the car entirely off the ground!
Many times, the boot can be replaced and the bearings and CV joint repacked with grease. This is a lot less expensive auto repair than replacing the entire axle, but remember that while the part itself is fairly cheap, there’s still a considerable amount of labor involved. If the joint itself is worn out, it can’t be repaired or overhauled. It will need to be replaced, or sometimes the entire axle/CV joint assembly will need replacement.
If you’re noticing noise or roughness in your FWD vehicle’s drivetrain, it could be a CV joint issue. It’s an auto repair you really don’t want to put off – give us a call and make an appointment with Black’s Tire & Auto Service in Raleigh, NC and let our techs have a look!
|CV Joints: What Are They? was written by Ryan Benton of Black's Tire and Auto Service|