th350 trouble

i have a 76 corvette with a turbo 350. it has a slow leak and havent figured out where its leaking so i have started it a few times when it was low on fluid, now the transmission will hardly grip for a few seconds when i first start i then it goes out. if i shut if off and start it up again it will grip for a few more seconds. im woundering if its the transmission itself or maybe the torque converter? any ideas

 

i'm woundring if you should put more fluid in it