fluctuating gas guage

I have a 97 s-10. The problem I am having is that the fuel guage is fluctuating radically. When I fill up the guage shows full, no problem. As I get about 50 miles out of the tank the guage begins to drop rapidly and by the time I have about a half tank left the guage is showing empty. Some days the guage works fine but most of the time it fluctuates badly. I've been trying to watch to see if dampness plays a factor but to this point it hasn't. I have not been able to pinpoint any set pattern. The rest of the guages have been working just fine with no fluctuations.

Your sending unit in your fuel tank is going bad.

SC

doubt this is the same problem
but my gauge is always going up and down in my '83 S-10

I guess the needle is weak or something, because when sitting or just idling the needle shows exact amount of gas, but when driving to turning, the needle slowly bounses around and goes up and down, but when stopped, it shows the right amount

your 83's gas tank is a little different, yours moves because the gas sloshes around... the 97's sending unit and pump (all one unit, available seperate from cheep after market companies... but not worth dropping the tank twice imho) are going bad as sc said