2002 Chev sub with 8100, 4l80e trans. Gauge goes to full when tank is filled. Will drop about normal to 3/4 while driving, then it stops. It won't move again until you have approx 6 gal of gas left . Then goes to 1/2 tank. Dealer has replaced sending units in the tank, has verified that gauge works with OBDII, and relaced PCM. End result: No change. Any ideas? It is still under warrenty, but what do you replace next?
Thanks for any ideas and comments.
Regards,
JimO