* Wheel Bearings: This is a very common cause. A worn wheel bearing will create a humming or groaning sound that increases with speed (and thus acceleration). It often sounds like it's coming from the wheel area, but the sound can travel through the car's structure. Check for play in the wheels – if you can grab the top and bottom of the tire and wiggle it significantly, that's a strong indicator.
* Transmission Problems: A humming noise that gets louder with acceleration could indicate problems within the transmission itself. This could be worn gears, low transmission fluid, or a failing transmission component. Often, transmission problems will also be accompanied by other symptoms like slipping gears, harsh shifting, or difficulty getting into gear.
* Driveshaft Issues: A worn or damaged driveshaft U-joint can also produce a humming sound, particularly under acceleration. This is less likely to be solely a humming sound; you might also feel vibrations.
* Power Steering Pump: Although less likely to be a *humming* sound specifically, a failing power steering pump can create a whine or groan that increases with steering input, which often occurs during acceleration as you're turning to maintain your lane.
* Belt Tensioner or Idler Pulley: While these typically create squealing or chirping, a severely worn or failing one *could* produce a low-pitched hum, especially under load (acceleration).
Troubleshooting Steps:
1. Check the Wheel Bearings: This is the most likely culprit. Have someone help you wiggle each wheel while you check for excessive play. Jacking up the car is essential for proper assessment.
2. Listen Carefully: Try to pinpoint the location of the sound as precisely as possible. Is it definitely coming from the front? Is it more from one side than the other?
3. Check Fluid Levels: Check your transmission fluid level. Low fluid can cause increased wear and humming. Also, check power steering fluid.
4. Professional Inspection: If you're not comfortable inspecting the wheel bearings yourself or you can't pinpoint the source, take your Impala to a mechanic. They have the tools and expertise to diagnose the issue properly.
Ignoring the issue could lead to more significant and expensive repairs down the line. Get it checked as soon as possible.
