Tran code 46 keeps coming up

What is your question?

After started, check engine light comes on and idles very low. Hum is heard. Diagnostic code 46 comes up under transmission codes. Shifts hard in reverse at times. Feels like its stuck in higher gear but it cycles through all gears normally. Replaced park/neutral switch and transmission valve body but problem still occurs. Big decline in gas mileage. Any suggestions/ideas?