During the late 1970's and the early 1980's, front-wheel-drive (FWD) vehicles became very popular for many reasons. FWD vehicles were more fuel efficient than RWD vehicles being built at the time. The FWD designs provided smoother drivetrain operation.

FWD vehicles generally do not exhibit many of the driveline vibrations seen with RWD vehicles. Front-drive axles have the following characteristics

Although FWD is smoother than RWD, the following problem conditions may occur and require diagnosis and correction:

Worn or damaged inner tri-pod joints may cause vehicle speed-related, third-order tire vibrations.

Tri-pod joints are so named because of their design characteristics. Tri-pod or tri-podial joints have 3 trunnions (or a trilobal spider assembly) that fit into a race or a cup. The assembly moves in and out freely in order to compensate for drive axle length changes during suspension travel.

Third-order tire-related disturbances can occur if the following conditions are present:

The worn joint creates 3 disturbances per 1 revolution of the axle shaft. Because the axle shaft turns at the same rate as the wheel, third-order tire-related vibrations will result.

Front-wheel-drive (FWD) hub and bearing assemblies can make a low, growling noise that increases with the vehicle speed. The tires and bearings can make a similar noise. The tires and bearings are vehicle-speed-sensitive.

In order to differentiate between tire noise and bearing noise, drive the vehicle in a straight line and perform several turning maneuvers side-to-side. A worn wheel bearing typically exhibits increased noise during turns. If the noise level increases during a right-hand turn, then the left-hand wheel bearing generally is causing the problem. The opposite is true for a left-hand turn. If a bearing and not the tires is the cause of the disturbance, the noise level increases when turning because an added load is applied to the bearing at the fault.