Hi,
Grumpy is correct, there is no such thing as a light traffic route around the city. We live in the Northwest burbs and our daughter lives in MI so we travel that way at least once a month. Take 80 or 94 west to 80/94 over the Illinois line to 294. when you get close to O'Hare airport turn onto 90 and follow that up through Rockford and over the border into Wisconsin. You'll find a lot of other RV's on the road so you'll be fine. Illinois has a lower speed limit for trucks and vehicles with trailers so watch the signs, they are usually about 100 feet after the car sign. Also check into getting an I-Pass for your TV. The tolls are half for electronic tolling and you can use the open road tolling and not have to stop for a cash booth. Only a $10 deposit for the unit and it's good all over the east and also in Indiana if you happen onto the Indiana toll road. Have a safe trip.