I just recently started driving the ol 940T and the gas gauge stays on full till it starts working again at 1/4 tank. BUT now it only stays on full. I ran out of gas in the driveway. I have driven it in such a way as to slosh the gas around in case something was stuck still no change. What can I check?? Thanks in advance for your advice.

 

The only real way to see what is wrong it to remove the sending unit and ohm it out.
That will tell you if it is the sending unit or the guage.