I just had my belt and water pump replace. I still have a squeak. After it warms up the squeak almost goes away. On warmer days here in the fall it is almost nonexistent. I think it is my alternator. I am not losing any charge and my gauge is perfect still. The mechanic thinks it's the cap and rotor. Any guesses?

 

Try tightening the belt a little more. The belt on the 4.0 has to be really tight. What ever you do, DO NOT spray the belt with belt dressing to try to stop the noise.

 

It may be a bad pulley or a slit in the belt. I had the same problem and saw it was ac pulley and happened most at first start and left when going about 45 MPH