If your vehicle is showing whining or humming noise that gets louder with speed, here are the most likely causes and the parts you'll need to fix each one.
A worn wheel bearing produces a humming or roaring noise that increases with vehicle speed and often changes pitch when changing lanes. This can sometimes be caused by over-torquing the spindle nut during a recent brake or axle service.
Uneven tire wear, particularly 'cupping', creates a rhythmic humming that sounds almost identical to a bad wheel bearing. Worn shock absorbers or poor alignment are frequent root causes of this wear pattern.
Low gear oil or worn carrier bearings in the differential will cause a whine that scales with speed, often changing depending on whether you are accelerating or coasting. If recently serviced, incorrect fluid levels can trigger this.
On rear-wheel or all-wheel drive vehicles, a worn driveshaft center support bearing will emit a high-pitched hum or whine right under the cabin that gets louder as you drive faster.
Low transmission fluid or a failing internal pump can cause a whine that increases with speed and RPM. This frequently occurs if the transmission was underfilled during a recent fluid and filter change.