727 noise from Reverse to Neutral and 3rd to Neutral when cold.

I would say you have a restricted trans filter. I have experienced this several times in the past. Once it was After I had just installed new filter and fluid. In every case it was when I would use the felt type original style filter. Many years ago I switched to the fine mesh screen type filters and have never had this problem again. It sounds like a whizzing type sound and is more noticeable when the trans is shifted to reverse.