engine noise 04 crown

i HAVE A 2004 CROWN WITH 43K ON IT ..IN THE LAST WEEK OR SO I STARTED HEARING A RATTLE SOUNDS LIKE COMING FROM REAR OF ENGINE I HAVENT LOOKED UNDERNEATH YET....I USUALLY HEAR THE RATTLE AFTER ABOUT 5MINUTES AFTER START UP AND AND ACCELERATION BUT VERY LITTLE AT HIGH SPEEDS...I WAS TOLD TO CK THE TORQUE CONVERTER FOR TIGHTNESS ANY OTHER SUGGESTIONS OR KNOWN PROBLEMS