2002 express 5.7 fuel guage jumps between over full reading around the 3 o'clock position to the correct level every few seconds...back and fourth...back and fourth. Changed bad fuel sender as it was stuck at the over full reading for several months prior. Contacts on fuel sending unit were deteriorated and making poor to no contact. Now this is a new problem.

 

GM had a problem with the stepper motors for the gauges around that time. My 03 Trailblazer had a speedometer failure. I replaced all 6 stepper motors as they are not expensive so as not to have to do the work again. If you can solder you can do it yourself.

 

It could be grounding somewhere. Or possibly a bad connection at the back of the cluster.
On our voyager, we had to re solder the circuit oard where the main plug harness is. Vibration caused it to get loose on those contacts...