Scotty, Back in the early 70's, my high school auto mechanics teacher told us to never idle an automatic transmission for long periods of time in drive or in park. He said it was best to idle the transmission in neutral as the transmission is under no load and free spinning, allowing the bearings to be lubricated and the oil to move freely in the transmission. His argument is that park stops the gears from turning and the bearings are having to spin without much lubrication from the transmission. What are your thoughts? Is neutral better than than park when idling for a lengthy period of time?
I've never heard of that. I happen to have the factory service manual for 1962 Rambler American handy and did a quick check of the section for the Flash-O-Matic transmission. The manual has detailed color diagrams of the hydraulic circuits and servos engaged for each operating mode with engine running. Park and neutral do not have separate diagrams which implies there is no difference in idling either way.
It might have been true in the 70's but it's obsolete advice now.
I don't think it was true even then in most cases. On the other hand GM had a bewildering number of different automatic transmissions in their cars from 1950s through 1970s, it's possible that might be the case for some of them.