Fuel gauge issues
 

My GF just bought a completely stock 08 Chevy Dmax 2500 4x4 LTZ. Truck runs great but when the truck gets down to half a tank it shows empty on the gauge. With the fuel light on couldn't put more than 18 gallons in. Before I drop the money on a new sending unit and drop the tank has anyone had this issue, what causes it and was their an easy fix?

My 08 gmc did the same pretty much. I'd fill it and it would read like 3/4 a tank and then I'd use maybe a quarter and it was saying it was empty etc etc it did weird shit. The dealership replaced the sending and works just fine now. I want to say that the mechanic there said there is some rails the float slides up and down on and one of them was actually broken. may be worth it to dropped it and pull the unit out.