I could write an essay on this topic. First off, the proper response and most correct response to this question of neutralling an automatic is simply don't do it.
This year alone I have had at least 6 cases where this has cost the drivers their transmissions and almost their cars.I will give only 1 example later in this opinion. During a pass in a high powered car the converter oil is very close to its boiling point, when you neutral the car at the top it has a similar effect to removing the rad cap on a motor that would not boil over if you had left the cap on as the pressure and flow is stopped right at the time you reach peak temperature, now the converter oil boils and aerates and blows apart the babbit pump bushing which is a controlling factor in converter efficiency and front seal oil control. Now every other pass generates even more heat, then the front seal is outta there, where and when it happens, who knows but I hope its not at 200mph. You wouldn't shut off your water pump or oil pump for your precious motor going through the eyes so don't do it to the trans.
The glide planetary system can and will subject the clutch drum to 2X the driveshaft speed providing the input shaft remains stationary (not likely) but the glide drums are small and they are less prove to explosions . I have seen them explode but kinda rare.
All other 3 speeds using a simpson planetary system using production ratios can exceed 2X driveshaft rpm providing the input shaft stops but the drums are larger and the designs are more complex and full of stress risers which lower their burst speeds greatly over a glide, they also use sprags and sprags do not think much of high overrunning speeds without lube.
Killing the engine or letting it run during shutdown, I really see no difference other than your now dead in the water if you need throttle to manueuver for whatever reason.
Here's another example , a guy who chose to neutral for some time eventually damaged his planetary from lube problems , he left the line and felt the car shudder and thought it was tire shake, plugged it into high gear and made the pass. Got to the top, clicked the motor off, neutralled the car then shortly after the rear wheels locked up almost crashing but got lucky.
Here's the diagnosis, car left and shit the planetary somewhat (shake) , plugged it into high (everything turns in the planet so its driving on some broken teeth that are hanging on) makes the pass, throws neutral (a glide has NO actual neutral, just a planetary, thats why glide cars rock so bad when you rev them in nuetral) motor quits the trans momentarily goes free then , it piles up and try's to restart the motor, it can't so the rear wheels lock up. Just one of many more examples I can give. I think I may be getting old and over cautious but regardless do what you want when you want, its your car, its your parts.
