It's my dream school.
Basic Information: 4.00 UW GPA and a 31 on the ACT.
You have a really, REALLY good chance. Commit early with early action and you're golden.
You should get admitted - no problem. However, if you are looking for a good academic scholarship you need to boost your ACT to 32. If you can get your ACT to 33 or better, you will have a good chance at getting into the U of Michigan honors program (if interested).
I was amazed to find out the difference a point or two on ACT can make in merit scholorship award $$$ at public universities. Generally a composite score of 33 or higher is where to be for top awards. I thought a 32 was good enough (decided not to retake the test) but, a 33 could have made a difference in the award amount.
Re-take the ACT, a slightly higher score may open a few doors.
I live across the street from U of M and most the kids in my district apply to go to U of M. Usually the kids with your qualifications get in no problem, however, you will need to make sure you tell them they are your first choice. Apply Early. A kid in my school had a 3.8 and a 35 ACT but was rejected because they assumed he wouldn't attend if admitted. They thought he would go to an ivy. So it is important to show your passion!!! but seriously if you apply early there is a 99% chance you will get in, seriously.
Looks good but make sure you REALLLLLLY want to go there and show it in all the essays and get a lot of extra cirriculars in...those matter a lot too! I'm going in the fall and can honestly say UM is one of the best schools out there! GO BLUE! :D