Could be a few things. Could be a miss in the motor. I had a burnt plug wire on my car that caused a similar shutter at lower rpm's. Could also be a clutch I suppose but I would think that it would happen in all gears if that was the case. If its specific to the gear then the only thing that is the different in 2nd gear really is the transmission gear itself. I would check the plug wires first, never know.
Not sure whether it's chugging or bucking. Can't say I know the difference. And I have no idea what a warped clutch feels like. It's an AODE if that helps. I will go check the wires though. Also I think I could use a new distributor and/or cap.