I have a knock in the transmission.  It mainly  happens when the car
is cold started in PARK. When I shift to R or D the knock stops. When
the engine is warm and is restarted the knock is usually not there.

The knock is not a steady knock like a valve tapping but rather like
an occasional knock like hitting the side of the transmission with a
small hammer.

I have had transmission shops look at it but they just wanted to
rebuild the thing.

Thanks for any help.