2001 Chrysler Van Knocking sound from the motor area

I have a Crystler Voyager 3.3 V6 and its starting to make a Knocking sound. I have dropped the pan from the motor and there is no indication of a spun barring. There is no metal shavings in the pan as well. Before dropping the Pan off I ran the motor and changed the oil to see if that made a difference in the sound. No change. The knocking sound only occurs once the van I revved up to or around 1,000rpm and higher. Putting it in gear the sound did quiet up a little bit quieter. Running the car till the motor warms up did not change the sound as well. My Guess is a possible broken Flex plate. But with taking off the small cover on the bottom you still cannot inspect around the crank to see if this is broken. Am I on the right track and if so whats the easy way to inspect this w/o pulling the motor?