muzzy1tmr

I have recently noticed a rattle coming from the engine compartment not exactly sure where the noise is coming from i had a mechanic look at it and he replaced the idler pully proclaiming that was the noise but it still happened then my neighbor a 5.0 enthusiast looked at it and listened 2 it with a stethascope to define exactly where this noise was coming from but at the time it didnt happen ****note this only happens on occassion and under a load******* i have heard there is a valve in the tranny that may cause this but i dont know this is the first pony and not to keen on just ripping things apart just yet does anyone have ideas my first thought wasw a possible wristpin but it would happen alot more than it does or would it????? if anyone can help please do... thanxx