air coming from this valve on trans help

my truck just started to have a air leak under it the other day so I went under to find this valve leaking.. the side of it is plastic and is cracked...I don't have a problem with it as far as shifting goes but it leaks all my air out the tanks in a few hrs...what is it called and bout how much does it cost???? is this something I can do at home????






thanks for any help guys

 

thanks now do I have to change the whole thing or can I just buy the plastic (yellow looking) bottom that's where the air is coming from it has a split on the side of it...or is there a way to take the plastic pcs off and check the filter?????

 

thanks I found out today that it is giving me problems when going from low to high side it pops right in ...I don't use the low side much so I will get it took care of this week end thanks for the info guys