I noticed today as I was putting the car in reverse there was some resistance and this clunking grinding noise coming from underneath the car. It's more noticeable from a cold start. The car has 50k miles. Any ideas?

 

I'll bet you didn't have the parking brake set and your car was on an incline. It sounds like the weight of the car was resting against the "park" pin in the transmission.

 

actually the car was parked level in the garage with the parking brake. I'll be taking it to my mechanic today and see what he has to say about it. I'll keep you guys posted.