E making a hissing sound on acceleration and when shifting

Hi all, I have a 2005 E 4spd auto with 138k on it. I’ve noticed this for a while now but didn’t really look into it until now. Upon acceleration, and it gets more noticeable the harder the acceleration, it makes a hissing noise, and when it shifts it almost sounds like its releasing air like an air brake system. Absolutely no clue where to check first, but any recommendations would be appreciated!