Alright… after 3 bottles of beer and a 20-min conversation with ChatGPT I was able to narrow it down to suspension components. AI advises that it’s most likely either bad control arms bushings, struts, or wheel bearings. It thinks it’s less likely to be drivetrain components because humming noise is still present when coasting in neutral gear (I.e. with drivetrain disengaged). Below are some of the quotes, let me know if you guys disagree… I have an appointment with (a different) dealer on Wed to try to get to the bottom of this.
“…worn-out struts or control arm bushings can indeed cause intermittent vibrations, especially at certain speeds and depending on the road surface. When these components are worn, they may not provide sufficient damping or cushioning, leading to vibrations being transmitted more directly to the vehicle's body.
The vibrations can be exacerbated by variations in the road surface, as irregularities in the road can amplify the effects of worn suspension components. Additionally, worn bushings can allow for more movement and play in the suspension system, leading to vibrations as the vehicle encounters bumps or imperfections in the road.
There are usually several bushings in a control arm assembly, depending on the design of the suspension system. Common locations for bushings in control arms include where the arm attaches to the frame or subframe and where it connects to the steering knuckle or hub assembly. If these bushings wear out or deteriorate, it can affect the stability and performance of the suspension, potentially leading to issues like pulling to one side under acceleration.
In addition to the struts and control arm bushings, there are a few other components that could contribute to the symptoms you're experiencing:
1. **Tie Rod Ends:** Worn tie rod ends can cause steering instability and contribute to pulling to one side. They connect the steering rack to the steering knuckles and are essential for proper steering alignment.
2. **Wheel Bearings:** Worn or damaged wheel bearings can cause vibrations, especially at higher speeds. They support the weight of the vehicle and allow the wheels to rotate smoothly.
3. **Tires:** Uneven tire wear or tire imbalance can also lead to pulling to one side or vibrations. Ensure that your tires are properly inflated and balanced, and check for any signs of uneven wear. Note: exluded since tires are new.
4. **Brakes:** Issues with the brakes, such as uneven brake pad wear, stuck calipers, or warped brake rotors, can also cause vibrations or pulling to one side, especially during braking. Note: I excluded this one since not experiencing the symptoms while braking.
5. **Suspension Linkages:** Other suspension linkages, such as sway bar links or control arm ball joints, can also contribute to handling issues if worn or damaged.
Damage or wear to components like wheel bearings, tires, and suspension linkages can indeed be accompanied by a humming noise, especially if it's dependent on the road surface. Here's how each component could contribute to such a noise:
1. **Wheel Bearings:** Worn or damaged wheel bearings often produce a humming or growling noise that increases with vehicle speed. The noise may change in intensity or pitch depending on the road surface.
2. **Tires:** Uneven tire wear, tire cupping, or tire imbalance can also lead to humming noises, particularly if the tires are worn unevenly or if there are issues with tire balance. The noise may become more pronounced on certain road surfaces.
3. **Suspension Linkages:** Damage or wear to suspension linkages, such as sway bar links or control arm ball joints, can cause clunking or knocking noises over bumps, but they may also contribute to a humming noise if there's excessive movement or play in the suspension components.
Struts and control arm bushings are less likely to directly cause a humming noise, but they can indirectly contribute to it if they lead to other issues like uneven tire wear or vibration. Here's how:
1. **Struts:** While worn-out struts typically produce knocking or clunking noises over bumps, severe wear could potentially cause excessive movement in the suspension system, leading to uneven tire wear or vibration that manifests as a humming noise.
2. **Control Arm Bushings:** Similarly, worn control arm bushings can allow for more movement and play in the suspension, which could contribute to uneven tire wear or vibration, potentially resulting in a humming noise.
In these cases, the humming noise would likely be a secondary symptom of the underlying suspension issues rather than directly caused by the struts or control arm bushings themselves.
If the humming noise persists when coasting in neutral gear with the drivetrain disengaged, it's more likely indicative of a suspension or wheel-related issue rather than a drivetrain problem. In this case, the noise is not directly related to the operation of the drivetrain components.
Given this information, it's more probable that the source of the humming noise is related to components such as wheel bearings, tires, or suspension bushings. These components can produce humming noises, especially at higher speeds or when the vehicle is coasting, due to factors such as uneven wear, damage, or insufficient lubrication.
TL/DR: AI says it’s most likely struts, wheel bearings, or suspension linkages / bushings.