So truck is a 5.0 and sometimes in idle only in park it makes a knocking noise and its getting to me and it never makes the noise at any other time. and one of my manifolds does have a small crack down the middle and i don't know if that's causing it but i have two new manifolds on the way and i was replacing them anyways.

 

I wouldn't even try to identify a possible knock until I got the cracked manifold sorted.

 

X2........

 

I agree with the above. I'll add that next oil change, you should cut the old filter open and look for metal in between the pleats.

 

is it your flex plate hitting your the guard shield? mine does 5.0 to an A.O.D if it was the manifold it would be always be there at idle and go speed up with your revs

 

ok. Really late response I finally finished putting my manifolds in. So after I put them in I seen a small I mean small crack in the y pipe near the start of the y. After I did that and got the manifolds in the knocking disappeared. If air was coming out of them. Wouldn't it be constant? I'm so confused..

 

Who knows. If the noise went away with the new manifolds, that had to be the issue.