hope i might find an answer to my knock/thunk here... my truck makes the the noise while idleing and while driving but with no consistancy some time it does it other times nothing and the sound does not have a pattern it may very from time as in time between thunks 30sec. to 2 min. apart. it sound like its coming from the drivers rear end of the motor. i opened the hood when i herd it and it sounded like it came from the passanger front of the motor. my desciption of this might be confusing but that is how confused i am.