Town Car V8-4.6L VIN W (1997)
Pinion Bearing: Testing and Inspection
Bearing Noise
BEARING WHINE
Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by damaged pinion bearings, which are operating at driveshaft
speed. Bearing noise occurs at all driving speeds. This distinguishes it from gear whine which usually comes and goes as speed changes. However,
if there is only one differential pinion bearing malfunctioning the noise may vary in different driving phases.
BEARING RUMBLE
Bearing rumble sounds like marbles being tumbled. This condition is usually caused by a malfunctioning pilot bearing. The lower pitch is because
the pilot bearing turns at only about one-third of driveshaft speed.
DESCRIPTION
Bearing damage will normally be obvious at disassembly. As noted earlier, differential pinion bearings make a high-pitched whistling noise,
usually at all speeds. However, if there is only one damaged differential pinion bearing, the noise may vary in different driving phases.
Differential pinion bearings are frequently replaced unnecessarily on axles with mileage under 24,139 km (15,000 miles) when correcting gear
noise. They should not be replaced unless they are actually scored or damaged, or there is a specific differential pinion bearing noise. Examine the
large end of the rollers for wear. If the differential pinion bearing original blend radius has worn to a sharp edge, the differential pinion bearing
should be replaced.
Remember that the low-pitched rumble of a damaged wheel bearing can also be caused by the exterior luggage rack or tires.
Rear wheel bearing noise might be mistaken for pinion bearing noise. Look at the rear wheel bearing carefully before tearing down the axle. Rear
wheel bearings are pressed into the axle housing tubes, making them more difficult to check. However the axle shaft is the inner race for the
bearing. If the bearing is damaged, the roller surface on the axle shaft may also be damaged. The rollers run approximately on the center of the
polished surface.
