Folks, you're making this way too hard. With the engine off in a vehicle with an automatic transmission you can turn the engine in any gear you'd like to. Any gear. Even Park. On a 2wd, 4wd, or Awd vehicle.

When the engine is not running, the trans pump is not pumping, making it just about impossible for any clutches to apply. Essentially, everything is neutral. Even if you had somehow managed to keep a gear applied, through some really odd aftermarket set-up (like a trans-brake), you would still be able to turn the converter, as the whole idea of a torque converter is to allow enough slip that the engine can happily churn away with a gear selected... you know, like when you stop at a stop sign.

Now as for using the vehicle's starter motor to do this, it's not too much of a problem either, as it will only engage in either neutral or park, and either of those will work just fine.

Perhaps the better question is "Does my torque converter even have a drain plug?" or "Why am I messing with my transmission to begin with?". I'd probably start with those and make sure I had them well answered before going any further.

MV