Strange sounds coming from 4l60e
 

Just had this issue start the other day. When the car is in gear and idle sitting still there is a sound (sounds like a squeal from a belt or pulley would make) coming from underneath around the trans. As soon as the car starts moving the noise goes away. Car shifts fine and the fluid looks and smells ok. It has me stumped what it could be. Cars sitting at 103k miles and dont think the trans was ever worked on besides a 2800 stall put on.

It might be the pressure regulator valve buzzing from being a little worn... it should be ok.

if thats it, is that something i can replace on my own easily?

In most cases the pr valve bore is worn in the pump and will require a reamer to install an over sized valve. However IMO this should only be done with the pump removed from the trans. Also a worn boost valve sleeve can cause issues as well. To be honest I would have to hear the noise to give you an honest opinion if the pump is the issue or not. If you would like to meet up some time I would be more than willing to listen to it for you. I have heard converters and also pump/converter bushings spin and make some crazy noises. Does it make this noise all the time or just when its cold and sitting still?