Q: Grinding noise with all gears except 1st, car always rumbles on 3rd gear.

5-speed Automatic transmission 2001 Ford Mustang, V6 Engine. Base Model. When I'm driving in first gear, the car drives fine. There's a whirring sound coming from the engine but I've heard other Mustangs of the same generation do the same thing. When it switches to 2nd gear, noticeably grinding noise comes up. I know the transmission is messed up because it jolts forward every time gears change. The noise sounds as if two discs were being rubbed together against sand. Almost as if there was dirt and sand being thrown around in my transmission while I drive. I have revved the car in Neutral an Park and the noise is not there. The noise always happens on every gear except first. As for the 3rd gear problem; the car shakes violently on 3rd gear. Especially when I downshifts on it's own when going down a steep hill. 3rd gear will always vibrate but vibrates even more when I give it gas.

My car has 197000 miles.
My car has an automatic transmission.