1996 Ford Explorer Making A Noise

I have a 96 EB Ford Explorer w/4.0. Recently it started making this grinding noise when in drive. Sometimes it sounds like its low on power steering fluid(which I have checked and its not)and then it makes its way to a constant squel. I have noticed that it is consistant with the rpm's not speed. The sound increases in volume as the rpms increase and then it will just go away. It only does it every once in a while. It always seem to do it on acceleration from a red light. Almost like it would be a bearing in one of the pulley's. But I have already replaced the idler pulley and belt tensioner pulley. Any advice or suggestions would be greatly appreciated.

I have a 96 EB Ford Explorer w/4.0. Recently it started making this grinding noise when in drive. Sometimes it sounds like its low on power steering fluid(which I have checked and its not)and then it makes its way to a constant squel. I have noticed that it is consistant with the rpm's not speed. The sound increases in volume as the rpms increase and then it will just go away. It only does it every once in a while. It always seem to do it on acceleration from a red light. Almost like it would be a bearing in one of the pulley's. But I have already replaced the idler pulley and belt tensioner pulley. Any advice or suggestions would be greatly appreciated.

does it do this just setting there idleing?

when it is in gear you can hear it sometimes at idle. But in park I can not get it to do it.

I have a 96 EB Ford Explorer w/4.0. Recently it started making this grinding noise when in drive. Sometimes it sounds like its low on power steering fluid(which I have checked and its not)and then it makes its way to a constant squel. I have noticed that it is consistant with the rpm's not speed. The sound increases in volume as the rpms increase and then it will just go away. It only does it every once in a while. It always seem to do it on acceleration from a red light. Almost like it would be a bearing in one of the pulley's. But I have already replaced the idler pulley and belt tensioner pulley. Any advice or suggestions would be greatly appreciated.

can you try to take belt off for a few and start it and see if you still hear it? that would tell you if it's one of the pulley's or in tranny? but don't let it run until it get's hot.

I will try that when I get a chance. This is my daily driver so it may be a while before I get a chance. But as soon as I do I will repost the results of what I find. I dont know why I didnt think of doing that. Thanks for the suggestion.

I finally got a chance Friday to take the belt off and see if it was in the front of the engine. After I took the belt off there was no noise at all. So I knew it had to be one of the pulleys on the front. So I turned all of the pulleys trying to figure out which one it was. None of them made a noise. So I put the belt back on and started the car. This time it sounded as if I was about to blow a rod. So I quickly shut the car off and took the belt off again. This time I noticed metal shavings around the alternator. Gave it a spin and it made an awful noise. Replaced it and now my noise has went away. Thanks for all the help. I guess sometimes you just have to wait till it gets bad enough.