fuel gauge not working

the gauge is on e but every once in a while it will go almost to 1/4 tank then back down to e

Kind of odd that it isn't one way or the other. The higher the resistance from the sending unit, the higher the fuel level reading. Therefore, if it sits on "E" there is little resistance...there is nearly continuity. You could have an issue with the gauge amplifier. The instrument cluster gauge amplifier electrically averages fuel sender readings so the fuel gauge displays actual fuel level and not fluctuations due to sloshing in fuel tank . The instrument cluster gauge amplifier is a small printed circuit board which latches into a pocket on the back of the instrument cluster. I do not know if it is still available...

i have two of the exact same truck and i tried swaping out the whole instrament panel and the same thing happens, and when i put the other panel in my other truck it worked fine

So then it must be a wiring concern. If you have eliminated the cluster and the sending unit, then there is absolutely nothing else. You should do some continuity checks from wiring connector to wiring connector.