Ok I've got a 2007 F150 5.4l with about 125,000 miles. When I get around 40 mph it knocks and shudders like hell. Been doing it for a while but i let it go as I only drive it about once a week. Yesterday gettin on 95 though, it knocked and shuddered again but this time no go. Wouldnt go above 45ish. I saw some people on here suggesting plugs, coils and such but when I put it in neutral and rev, it sounds goddamn beautiful. Sooo any help for my poor *** or am I screwed?

 

Your torque convert broke.

 

I doubt it's the torque converter. It is most likely plugs and/or coils. Revving it in neutral is meaningless. You won't notice a miss there.

 

Also clogged cats can cause this.