My truck has been making some noises when I'm driving at 40-50 mph range. The noise is noticeable in all gears but it changes from medium to high-pitched whining depending on the speed. At speeds higher than 50 mph, the noise disappears. It would also go away if I let go off the gas pedal. I had the differential fluid checked and it looks okay. I thought it might be caused by the differential. What do you think?
You are correct to suspect the differential. Other parts of the undercarriage, such as the tires and wheel bearings, usually result in a noise that persists during both acceleration and deceleration. Whining and howling noises are usually related to the differential gears and happen when the vehicle accelerates or decelerates. A pinion bearing is also a likely cause. The only way to thoroughly diagnose such a noise is to hear it in person. I suggest you have a trained professional, such as one from Your Mechanic, do this for you.
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