Transmission not smooth.

[chinlai]

Just had my transmission rebuilt a few months back, and recently I've been noticing that the car does not shift gears too well when the engine is cold. I've also noticed that when I let the car roll down a hill, it tends to jerk a little when shifting. I've been told my the mech that its probably due to the torque converter, but from what I can gather about the functions of a torque converter, I don't understand why it could be that part. :dunno: Does anyone have any suggestions as to what could be the problem?