James,

That would be quite a jolt when the automatic transmission (AT) went into gear with the engine running overspeed. And unlike a manual transmission where you would select the highest gear and slip the clutch, the AT would go into the lowest gear and put an extremly high torque on the drive train.

The AT would not stop the engine but it would slow it down if everything survived the initial jolt. The transmission fluid in the torque converter (TC) would get very hot quickly because all the energy from the engine would be converter to heat in the TC. It would be the same as applying the brake and the accelerator at the same with the AT in gear. The engine would run faster than idle under load but it won't stall.

The stall rating of a TC is between the input and output of the TC not when it will stall the engine. A TC will not stall an engine because it is designed that when the engine is at idle speed, the TC puts practically no load on the engine.

P E H