FUEL gauge won't go all the way to full on a new instrument cluster 2005 LC (1 Viewer)

[tdale1316]

Hey guys, I just swapped out my cluster thru the toyota program that allows you to buy thru the dealer. I swapped it out myself but have not driven much . Could be coincidence but last time I filled the truck the gauge showed just under a full tank. I had driven only 212 miles and the truck was LOW so I pulled in to fill her up. She only held 17 gallons and I filled it slowly. I am wondering could it be the gauge or is it the float or sending unit? The info meter on the NAV screen said 22 miles to go? So this makes me think it could be the sending unit. I am letting one of my sons use the truck so I kinda want to get to the bottom of it. Any ideas how to test gauge vs sending unit? Does the fact the trip meter in the NAV screen showed low fuel point towards sending unit? Thanks in advance