Transmission Problems

I have a 2001 impala LS 3800. When first starting the car car this is a grinding type noise that comes from the transmission area. It only last about 30 seconds and then goes away. Wondering if this could be a bad torque converter. Car also bucks under 50 percent acceleration around 30-50 MPh like the rev limiter is engaging. any ideas?

This bucking can be caused by an ignition problem or a trans issue, only a full scan and a road test by a pro will reveal the source, it may or may not be connected to the whine. How many miles and what is the service history?