I've head that a flexplate or torque converter problems can sound very much like engine mechanical problems. My 4.6 '97 does have a louck knock right at start up and at 1500 rpms and above w/o loosing oil pressure. Using a scope I able to determine the knock is loud near the back of the oil pan and on the tranny housing. Any suggestions on how to differentiate between these two issues?

 

there is a rubber plug in the bottom of the bell housing on the transmission u can pull that plug and see the flexplate and converter. u can wiggle them and see if its loose. but cold start up rattle is probably piston slap. the romeo 4.6's were kinda prone to it.