It's making a sound like bearings rubbing. Is this normal or should I be concerned It is a 2001 with JL chip, JL 3lb lower pulley and PSP cold air. The truck runs like a raped ape so is was just wondering.

 

Mine makes a noise similar to that. I think it is pretty common.

 

This condition is commonly referred to as cavitation in the blower snout. It is somewhat common, affecting approximately 20% of 2001 Ls, usually when a lower pulley is added. I believe the tolerances of the blowers were tightened up for 2001;some left the factory a little tighter than others, hence the noise.

My 2K1 Lightning had the same condition, even before installing the lower pulley. When the lower pulley was done, the noise worsened to the point where the blower literally sounded like a diesel engine. It occured only in Drive @ idle.

To temporarily help the problem, I had my Idle RPM raised to about 700 or so. This reduced the clattery noise by 90%. Subsequently, with assistance from Jim D'Amore@JDM, I was able to permanently eliminate the cavitation 100%, and at normal idle.

 

Canyonrunner, thanks for the great explanation of what the noise is. I've been hearing something similar on my 01. As you say, only in drive @ an idle. Give it any little bit of gas and it magically disappears.

Bob