Can a torque converter be knocking kinda loud from lack of transmission fluid?

i just got the transmission back in my truck it's an auto and i don't have enough transmission fluid in it yet. it takes like 7 quarts and it only has 4 in it rite now(im not driving it until i get more) but it has been knockin since i got it back together. while it was apart, the water froze in the hoses but i checked and everything looked ok when i got it defrosted and drained. could that cause something to break and knock? my stepdad thinks its either a broken rod(cuz thats wat it sounds like) or no fluid in the torque converter( i really hope thats wat it is cuz that was a pain in the *** to take apart and put back together)I checked everything for leakin water while it was running and there was none. there was no water in the oil either. thanks