Here's a question for you hemi experts. For a while now my truck makes this rattle noise when under load for example going up a really steep hill under moderate throttle. Sounds kind of like a small pebble being shaken in a soda can lightly. Seems to happen around 2500 rpms and will go away if I get on it more or let off of it. No driveability issues at all. I tend to forget about it because you can't hear it with the windows up at all. Checked for loose heat shields and all seems tight. Could it be spark knock? I figured the timing would cut back if it was that. Only 11k miles so I cant imagine it being a manifold leak yet
Update: removed the heat shields over the weekend and filled it up with Sunoco ultra 94. Still making the noise. Narrowing it down as much as I can, it only does it when the truck is completely hot(driving for 30+ minutes) and it's under load (large uphill run). Happens as soon as it downshifts and lasts until it upshifts one gear or I put it to the floor. I'm almost leaning towards either a idler pulley or tensioner causing it do to the sudden increase of engine speed. Neither pulley has a any roughness and only marginal bearing play.
Update: removed the heat shields over the weekend and filled it up with Sunoco ultra 94. Still making the noise. Narrowing it down as much as I can, it only does it when the truck is completely hot(driving for 30+ minutes) and it's under load (large uphill run). Happens as soon as it downshifts and lasts until it upshifts one gear or I put it to the floor. I'm almost leaning towards either a idler pulley or tensioner causing it do to the sudden increase of engine speed. Neither pulley has a any roughness and only marginal bearing play.