i used some spray on my belt. The belt did make some noise on startup, but after i used the spray its quiet. I dont know the name on the spray.
http://www.ehow.com/how_5723375_fix-noisy-fan-belt.html

 

Crank Jump? as in excessive play in the crankshaft bearings?

 

Maybe your "crank jump" is a worn out harmonic balancer

 

I am not sure of the cause, I am new at this and my Jeep is what I am learning on. I can see the crank pulley "jump" forward when I rev the engine and when I do that I can hear the the noise. I am hoping it is not the crank making the noise and I am being told by my brother in law who is a mechanic that it is the belt because it is twisting when the crank jumps

 

A bar of soap works lol. Mine squeals when I turn the AC on when its warming up, but after a minute or two it stops. I just turn the stereo up.

 

Perhaps N20Jeep got it right when he mentioned the Harmonic Balancer. Maybe its loose? Maybe the pully bolted to the front of the Harmonic Balance is loose.?. What do you see move, just the pulley that the belt is on or both the pulley and the larger round thing (Harmonic Balancer) the pulley is attached to?

 

What I mean is the rubber insulation inside the balancer could be worn out

 

Yes, but how would that affect the pulley? The pulley is bolted to the center of the Balancer which is in turn affixed to the crankshaft. If the rubber insulation failed, the outer ring, while highly improbable, could possibly slide forward and rub on the belt. I have never seen it happen but that does not mean it can't happen.

Thats why I asked the OP what was moving.

 

His harmonic balancer is one piece. Its not a 2 piece setup

 

This.