Drivetrain Related:
* Wheel Bearings: This is a very common cause of humming. The noise often increases with speed and can change pitch depending on how hard you're turning. A bad bearing will usually feel rough to the touch when you try to rotate the wheel (with the vehicle jacked up and secured, of course).
* Transfer Case: Problems in the transfer case can cause a humming or whining sound, especially in 4WD. This is more likely if the noise is more pronounced when engaged in 4WD.
* Differentials (Front and Rear): Similar to the transfer case, worn gears or low fluid in either differential can create a humming noise. This is often speed-dependent.
* Axle Shafts (Drive Shafts): CV joints (constant velocity joints) in the axle shafts can produce a humming sound, especially when turning. A clicking sound along with the hum is a strong indicator of a failing CV joint.
* U-Joints: Worn U-joints in the driveshafts can create a rhythmic clicking or humming noise, particularly at higher speeds.
Other Potential Sources:
* Tires: Worn or improperly balanced tires can cause a humming noise, especially at higher speeds. Rotate your tires and check for uneven wear.
* Brakes: While less likely to be a hum, dragging brakes can make a low-pitched grinding or groaning noise. Check your brake pads and rotors for wear.
* Exhaust System: A loose or damaged exhaust system can sometimes create a humming or resonating noise, especially at certain speeds.
* Alternator/Belt: A failing alternator or a slipping serpentine belt can sometimes create a high-pitched whine or hum.
Troubleshooting Steps:
1. Check the speed and conditions: Does the hum change with speed? Does it happen only when turning? Is it worse in 2WD or 4WD? This helps isolate the potential source.
2. Listen carefully: Try to pinpoint the location of the noise. Is it coming from the front, rear, or both sides? This will help narrow down the components.
3. Inspect visually: Look for anything obviously damaged or loose in the drivetrain, exhaust, or undercarriage.
4. Jack up the vehicle (safely): With the vehicle securely supported, check for play in the wheels and listen for noise while rotating them.
5. Check fluid levels: Check the differential and transfer case fluid levels. Low fluid can cause significant noise.
Important Note: If you are unsure about diagnosing the problem yourself, take your Suburban to a qualified mechanic. Ignoring a persistent humming noise can lead to more serious and costly damage.
