Detroit, MI to Milwaukee School of Engineering buses and trains from $57

Here are some trips other travelers have found on Routefriend.
$57
9h 6m
1 stop
Amtrak
$58
8h 16m
2 stops
Amtrak Greyhound
$78
12h 49m
4 stops
Amtrak Greyhound
$104
9h 10m
1 stop
Greyhound