GMC Repair: defective gas tanks on 99 jimmys, gas gauge, gm dealer

Question
I have just purchased my 2nd '99 jimmy to discover the gas gauge gives very sporadic readings when the tank is between 1/2 and 3/4 full,just like my last one did.  Is there any kind of hidden warranty from the manufacturer since this seems like a common problem in jimmys?

Answer
no hidden warranty that i know of, I own one and work at a GM dealer, we have had good success with the release of an updated level sensor, most that we install the updated part on do not return.  Mine does the same thing, I just have learned to live with it, no sense taking it apart until it needs another fuel pump