Fuel gauge/sender ? 65 Dart

Fuel gauge issues seem to be pretty common on this site....so here goes another one.

I replaced my sending unit figuring that was the reason the gauge wasn't working. Took the unit out and sure enough, old one was trashed. Took the instrument cluster off and cleaned the connections. Hooked it all back up, put a few gallons of gas back in the tank and the needle moved! But....it shot up to a full tank with only 2 gallons in :mad:....went to the gas station, filled it up and gauge still read full until i was halfway home and then the gauge just "died" and fell back to E. Haven't been able to get it to move again.

Just wanted to know if anyone has seen this before...I can't figure it out and it's jamacin me crazy....Car is a 65 Dart