TroubleshootingStep 1 - Check the Tire Wear Pattern. A tire with a scalloped pattern on the tire will cause a whirring sound at speeds over about 45 MPH. This tire condition is caused by a combination of worn struts or shocks and or tire imbalance. If a tire is not being controlled evenly the tire will vibrate causing the tread to contact the ground inconsistently. This inconsistent contact with the road causes the tires tread to wear unevenly. (Cupping, tire example on the right). To check for this condition, take your hand and pass it over the tire tread, it should be smooth. If high and low points exist the tire is cupped and needs to be rotated or replaced depending on the severity of the cupping condition, and the suspension repair accordingly.
Tire Wear Patterns Step 2 - Inspect Axle Bearings As a front or rear axle bearing fails it will create a grumble or whirring sound. To check for this condition the axle bearing must be removed and disassembled to inspect for metal shavings inside the bearing. This is a sign the bearing has failed and needs replacement. A quick way of checking for a failed axle bearing is to safely suspend the vehicle so there is no weight on the tire. Grab a hold of the tire with both hands and shake it back and forth (top to bottom). If the wheel seems loose further inspection is required. This method does not always work because sometimes axle bearings can remain tight even though they have failed, but this method will detect most failures. In the event of an axle bearing failure it is highly advised to replace the bearing immediately to avoid catastrophic failure. Depending on the type of bearing you are servicing a special puller tool maybe required.Step 3 - Inspect Rear Axle Pinion Bearing. The gear that drives the ring gear is called a pinion gear. The pinion gear is supported by a primary and secondary bearing. When the pinion bearing fails it will cause a rumble and whirring sound in the main rear carrier. To check for this condition the pinion bearing must be removed and disassembled to inspect for metal shavings inside the bearing. This is a sign the bearing has failed and needs replacement. A quick way of checking for a failed bearing or pinion bearing that could be failing is to grab a hold of the drive shaft near the rear driver with both hands and shake it back and forth. If the shaft seems loose further inspection is required. Disassemble to inspect bearings and replace rear differential or bearings as needed. (Note: a press is needed to replace the pinion bearing)