i just bout a 2000 xj with 138xxx miles on it and a 4.0l.
when I get up to about 65 mph and I let off the gas a high pitch noise starts and it doesn't stop until I press back on the gas and I believe it is coming from the front of the engine like at the belts. any help would be appreciated.

 

Is it like a chirping sound? If so i would actually look at the front U-joints.

 

it's not a chirping sound. it a high pitch squel type noise. but it only happens at about 65 mph when I let off the gas

 

Hmm, could be the fan belt. Is it nice n' tight?

 

Mechanic can quickly tell you if you need new u-joints, hubs, etc. Let him diagnose for free.