I noticed what sounded like a rod knock coming from the truck yesterday. It seemed to be coming from the back part of the motor, close to the tranny. I know our flex plates arent exactly the strongest things so I took the inspection cover off the trans to see if I could get a glimpse of something. The knocking got a lot louder as soon as I took the plate off, but of course I couldnt really see anything. Seems obvious that the flexplate is broken, but without pulling the trans to know for sure I would'nt mind hearing some other opinions. I guess all the plowing this winter was a little more abuse than the old stock plate could handle. Oh yeah, as a bonus I found that my fuel pin diaphragm had a small tear in it too.

 

Your description fits what I experienced.

 

Could also simply be loose Torque Converter bolts.

Try tightening them first, then I would say Broken Flexplate.

 

A broken flex plate sucks, but it is a good excuse to upgrade the torque converter. I guess I should be calling Goerend soon.