Tahoe2012LTZ

I tried that as well. It helped a bit, but still could only fill at half throttle.

2012 Tahoe can only take about 10 seconds at the pump before you can actually hear it backing up in the filler neck, and it clicks off. If I pump very slowly its Ok. No engine light, or codes present. I've read that this could be the Vent Valve solenoid in some of the earlier trucks (2007), but haven't seem any write ups for newer (2012) trucks. Anyone else with same issue on 2012 era trucks, and what ended up fixing the issue?

Sounds like it could possibly be cab body mounts. If you Google "Dealing with a Caddy clunk" there is a nice write up on this. I had it on my 2012 Tahoe.