On my 85 sierra, it has two tanks and when either one of them are full( all 16 gallons each) the gas gauge only reads 1/2 way. the switch seems to work fine so it isnt getting stuck in between. I was going to check the senders, a bit expensive, but since they both seem to have the same problem, i am thinking it is the gauge. Ive had many old trucks, and they all seem to have problems with the gauges, especailly when we lift them. simular problems anybody? whats it like to change out the old gauge or put a different one in?