ATPLwannabeboy,. .. .I fly the 737 at present, and I assure you that the autopilot does not trim for mach tuck. This is achieved by the Mach Trim system which then commands re-datuming of the Elevator Feel and Centering Unit to move the elevators. As it happens the system is armed above 0.615M, but the aircraft can be flown to (3-4-5) 0.74M (NG) 280kts/0.82M with the system inoperative, without trouble.. .. .I can assure you that the 737 autopilot system does not use AoA information.