Anyone know why legendaries keep dropping level 40 but nothing else?

They wont go higher until you hit lvl 60 zones. Then 60 legs at 70 zones. At least I'm pretty sure how it works.

the item level changes on items. the required level to equip has different thresholds. uniques are like 5 15 35 40. legendary has different ones. this value doesnt determine stat ranges, the item level does. goto your options to enable "show item level" so you can know.