if the 205 k miles are accurate on the transmittin, it is worn out twice.
The filter may be clogging up, to cause full loss of pressure.
have you dropped the pan? A filter change is not expensive, may be worth the effort as a test.
when removing the pan from trans in that truck, be careful with shift solenoids. You can break them trying to get pan off trans around exhaust pipe IF the pipe crowds the pan as most GM trucks
Yesterday is history.