AUTO BREVITY


Front Wheel Drive Constant Velocity Joint (CV Joint)

Automotive Mileposts
Image: 1980 Cadillac Fleetwood Eldorado body diagram

See through body diagram of a 1980 Cadillac Eldorado Coupe, which came with front wheel drive

CV Joints supply power to the front drive wheels on cars with front wheel drive.

A built-in torque dampener on the right shaft prevented damage by acting as a shock absorber to the front wheel drive components.

Replacement parts do not normally have this shock absorber, which can be a real concern under some conditions.


Constant-velocity joints, or "CV joints" are used in most front wheel drive applications, as well as many four wheel or all-wheel drive vehicles, and on vehicles with rear wheel drive that have independent rear suspension systems. A CV joint transmits power from a central rotating shaft to another shaft by way of a variable angle joint consisting of multiple bearings that allow angular rotation of the second shaft (as when turning the front wheels to go around a corner) while maintaining a consistent rotational speed.

The CV joint is protected from dirt by a rubber boot which also keeps the joint packed in grease. An early tell-tale sign that the boot has failed is a clicking noise while accelerating at the same time as turning a corner. This clicking noise indicates the joint is no longer being properly lubricated, and is a warning to have the joint serviced quickly.

On the first General Motors cars with front wheel drive, the 1966 Oldsmobile Toronado and 1967 Cadillac Eldorado (as well as the variants that followed), the front constant velocity joints were slightly different. The right CV joint had a torque or shock dampener, which acted like a shock absorber for front wheel drive. A cylindrical component located on the right side joint connects the two pieces together by setting them in rubber. This rubber cushions the two pieces to prevent them from damage in the event of a sudden jolt.

Why is this necessary? Picture this: You're driving along in your 1969 Cadillac Eldorado, and the roads have been partially cleared from an ice storm. Sections of the road where the ice has melted are dry, but there are still large patches of ice that are very slippery. You pull up to a stop sign and come to a complete stop. Then, as you begin accelerating away from the stop sign, your left front tire is on dry pavement, but the right front tire is on ice. The left wheel moves the car forward, while the right wheel spins on the ice. Suddenly, your right front tire hits a dry patch and has traction. That "jolt" can damage the front CV joints if there isn't a way to absorb and dissipate the energy that the sudden shock of traction delivers to the front wheel drive components.

Most of the currently available replacement parts do not include this shock dampener on the right side CV joint. If you live in an area where you aren't often exposed to sand or gravel on the road, or wet or icy road conditions, you may never need the dampener and won't notice any difference without it. However, if you live in an area where one or both wheels might be subjected to a loss of traction followed by an immediate, sudden jolt when the tire finally does grip the road, you should be aware that conditions like this can damage your CV joints.

Before buying replacement parts, you might check to see if your CV joints are original, and if they are, determine if there's a shop that can rebuild them locally, retaining the shock dampener. It's a nice thing to have when you need it, even if that may only be on a very rare occasion.

NOTABLE CLASSIC LUXURY CARS WITH CV JOINTS

LEGEND:
EOP = End of Production

1985-EOP Buick Electra
1979-EOP Buick Riviera
1985-Current Cadillac (except 1985-1992 Fleetwood Brougham)
1967-EOP Cadillac Eldorado
1966-EOP Oldsmobile Toronado
1985-EOP Oldsmobile Ninety-Eight