[vertbird]

76 Trans Am. Fuel guage has suddenly become hyperactive. Rocking the car, going round a corner, braking etc all cause the guage to jump around. If sitting still, it's accurate. Is there some type of capacitor that should "dampen" how quickly the guage reacts or is it something with the sending unit in the tank?

[Peter Serio]

The only dampening effect in the fuel gauge system is a small amount of glycerin paste put inside of the nylon former around the magnet before the wire is wound around the center core of the dash gauge. It is intended to last for a long time but on a car from a hot climate or (perhaps a trans am with T-tops) it is possible to boil the fluid out which would case exactly the symptoms you describe.

Another possibility is the tank sender is bad, that or the sender's black ground wire has come loose or the trunk pan steel; where the wire attaches to is very rusty or corroded.