Whenever I accelerate really really quickly (not quite pedal to the metal, but close), when I hit the upper RPM range (as tends to happen on my automatic transmission) I hear a terrible grinding noise, at which point I let off the gas a bit cause I dont want to blow up my engine. The sound SEEMS to be coming from the engine, however it could well also be the transmission, I'm really not sure. Do you guys have any thoughts?

Thanks

 

Floating valves?

 

Check your tranny mount.