I have a 2004 jeep grand cherokee 4.0L that is overheating while im drivimg or idle. The fan turns on and off as it pleases. Just replaced the thermostat and high and low relays with no luck.

Good chance your radiator is partially obstructed internally or externally (check front of condenser for bugs leaves etc and between condenser and radiator for same). 4.0's tend to internally rust and send rust particles into the radiator core. The radiator itself is actually smaller than it should be and therefore very sensitive to obstructions, Sometimes flushing with a good chem cleaner will help other times, you need to have a radiator shop do that. After doing the normal flush, disconnect the radiator from the engine entirely and run water through it in both directions. I generally remove them so it can be turned on it's end so debris can fall out while doing that.
Assuming that you see no white smoke from the tailpipe, have installed the thermostat in the right direction (spring towards engine) and have no leaks, that should help.
Your fan is controlled by the computer and comes on when the computer sees higher temps. Only time fan should run full time is with a/c on.