When I am on the highway or road and I am going over say 40-50 mph and I come to a red light and have to stop relatively abruptly...once I stop I hear a humming sound coming from underneath my car and it sounds almost as if the transmission or something is still spinning. It takes about 5-10 seconds to slows down (humming softly while it does) until it eventually stops and the sound goes away. It sounds as if something continues to spin at the same rate as it was spinning when going 40-50 mph even though the car has stopped moving forward. Any idea what this could be?

 

Auto or manual transmission?

 

I have an automatic.

 

I'm guessing it's not the transmission you're hearing, but something else. Possibly the radiator fans? Possibly the engine idle speed taking a bit of time to adjust? Possibly the air conditioner compressor cycling? It's hard to say exactly what it might be, but if the car is generally behaving as it should, I wouldn't worry.

 

What would be spinning if it were the engine idling taking time to adjust because between your three possibilities, it sounds the most likely based on the sound im hearing.