The last time I was in the Chicago area (September), I monitored Chicago F.M. stations as I was driving SE to Indianapolis.
Most faded out, typically, around Lafayette / West Lafayette, although I got a little extra bounce from WXRT as I recall.
However, I was able to monitor 87.7 to just about the Indianapolis beltway; on a lark, I checked out 87.7 while driving east of Indianapolis, and 87.7 FM Chicago was still there, in and out. Finally lost it for good about 30 miles before the Indiana/Ohio state line.
Perhaps it's the result of comparatively few stations on 87.7 and a slightly lower frequency. But I thought the station had amazing coverage, even as I was driving TO the Chicago area from LaSalle-Peru.
While in the Chicago area, the audio sounded fine. Of course, something could've happened since!