my friend has a 99 cherokee and just recently we noticed when he accelerates hard there's a loud grinding noise it sounds like metal to metal almost like his fan blades are hitting something but we checked and couldn't find anything at all!! it has been driving us nuts because we can't find any sign of anything rubbing or anything it doesn't happen when he accelerates slowing only when he punches it and it goes away right away anyone know what the hell it could be please?!?

 

Only when he is slowing, as in braking? Need a little more info (and maybe less run-on sentences, please). Where does it sound like it's coming from? Front, rear, left, right, etc.

At the beginning of the post you said it happens only when accelerating, and then contradicted yourself. Which one is it? Accelerating or braking?

 

sorry, it only happens when he accelerates fast and jumps it off the line hard, if he accelerates slowly it doesn't happen. it sounds like it is definitely coming from the front

 

It has worn or broken engine mounts.

 

That was my first thought. Mine does this if I step on it too hard without thinking because of the bad motor mounts.