While my car doesn't exhibit any problems during driving around the city, it has issues on the highway. At speeds 50-55 mph, I've noticed this deep, bass-like noise. There is no check engine light illuminated on the dashboard. At higher speeds, the noise disappears, but the driving sound of the car is different. If I slow down to around 55 again, the noise can be heard again. The car has gone around 65,000 miles. What do you think is causing this? Thank you.
Without being able to hear the sound and also with no TSB’s (technical service bulletins) out from KIA for known issues that match your issue, it will be hard to make an accurate recommendation.
Deep rumble sounds are often caused by an imbalance of a driveline component when it hits a certain frequency under load. Possibly the use of chassis ears can help narrow down the area where the noise is occurring. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will have the tools and experience to identify the type of noise, and then carry out the diagnosis of the noise to locate its source and correct it.