Can I simply drain off excess auto transmission fluid?

Yes, you can drain excess automatic Transmission Fluid, but it's important to do so carefully. Overfilling can cause issues like foaming and erratic shifting, so it's advisable to check the fluid level while the engine is running and the transmission is warm. Use a proper method, like a fluid suction pump or a turkey baster, to avoid spilling, and ensure you follow the manufacturer's recommendations for fluid levels. If unsure, consulting a professional or referring to the vehicle's service manual is best.