Bearing Whine

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2004 Mazda B4000, 2004 Mazda B3000, 2004 Mazda B2300, 2003 Mazda B4000, and 2003 Mazda B3000. However, it is still accessible from the selected car via links, so may be relevant.

Bearing whine is a high-pitched sound similar to a whistle.
It is usually caused by worn/damaged pinion bearings, which are operating at propeller shaft speed.
Bearing noise occurs at all driving speeds.
This distinguishes it from gear whine which usually comes and goes as speed changes.
As noted, pinion bearings make a high-pitched, whistling noise, usually at all speeds.
If however there is only one pinion bearing that is worn/damaged, the noise may vary in different driving phases.
Pinion bearings must not be replaced unless they are scored or damaged or there is a specific pinion bearing noise.
A worn/damaged bearing will normally be obvious at disassembly.
Examine the large end of the rollers for wear. If the pinion bearings original blend radius has worn to a sharp edge, the pinion bearing must be replaced.
NOTE: A low-pitched rumble normally associated with a worn/damaged wheel bearing can be caused by the exterior luggage rack or tires. A wheel bearing noise can be mistaken for a pinion bearing noise.
On 4x2 vehicles, check the wheel bearing for a spalled cup, and spalled/damaged rollers. Replace the wheel bearing if any of these concerns are detected. See WHEEL BEARING INSPECTION .
If the wheel bearing is damaged, the roller surface on the axle shaft may also be damaged. Replace the axle shaft if any damage is detected. On 4x4 vehicles, check the wheel bearing for rotating smoothness and end play. Replace as required. See WHEEL HUB (4X4) REMOVAL / INSTALLATION .