Fuel Gauge Help!

I put in a new sender.....correct ohms

Installed a new Auto-meter gauge under the dash...correct ohms
Installed new ground strap.

I fill her up and the gauge goes to full

Drive 50 miles or so and the needle is at 1/2 or a little below.

Drive another 25 or 30 miles and she is less than a quarter.

Stays there for a long time. Fill it up when it hits 1/8 of a tank
and it only takes 9 or 10 gallons.

The only thing I didn't replace was the wire from front to rear.