P0736 and po732 Mitsubishi - galant 2003

Question

i first had a problem when arriving home with no issues or warnings went to park and no reverse, then no drive, i thought i'd at least change the fluid and filter but i have no easy filter and no drain plug? so i open the pan and see 5 solenoid on a block, deciding to atleast check operation of them, one while in reverse which i thought was a grinding noise before dissaembly was chattering, so i know they dont chatter so i replaced it and it drove fine for a few miles, a day or two later went to drive car made it around a corner and suddenly lost everything, as if i was in neutral with no change in engine, some how it grabbed reverse and i got it home, only at this time is my engine light on, what are some possibilites for this failure