Gas Gaue Does Not Read Correctly

Hey group i have a 87 gmc suburban and every since i bought my truck which i would say has been about a yr ago my gauge has never read properly i have dropped my tank several times and my gauge still does not read correctly for example i will be like 30 bucks in and my gauge will stay on e or move a lil past e and when my truck is off the gas gauge hand itself is way past e if anyone knows how to correct this problem please post im desperate

when you say you droped your tank, did you do anything besides drop it, like change the guage, or just drop it.try going to a yard and getting a new guage for the dash, first tho check the sending unit voltage with an ohm meter with the unit removed. drop the float to the bottom with the ohm meter attached then move the float up, the meter should change smooothly. if it doesnt its the sending unit replace it. if it does reconect the meter to the gauge wires and do the same test. if the meter moves smoothly its the guage. if it doesnt its the wires