i believe its coming from the trans but im not sure i have a 1999 f150 lariat 4x4 5.4l that makes a rattling noise during acceleration its made the noise since ive had the truck but getting louder and more frequent, if i let off completely then mash back on the gas sometimes that stops it for the time being so i guess i just want to know if anyone else has had the same problem or knows whats causing it, thank for the help

 

To rule out spark knock, put a tank of high octane gas in it.