Trans noise

[Shatar4]

I have a 71 Challenger with a 505 stroker. The trans is a 727 with a fwd manual valve body. Recently the trans is making a "rubbing" sound only when I put it Neutral and drive gears. I had pulled the inspection plate off and checked for flex plate bolts that were loose but none were. I changed the fluid and filter.  Any other ideas i should be checking/