If those are separate tickets (not sure from your description..AA to TK? Sounds odd.) I'd be reluctant to reduce the time in between to 2.5 hours. If separate bookings its NOT a connection and you have no protection if the flight to ORD is delayed badly.... Having said THAT..... if you have to check in for the TK flight at ORD you might find you cannot do that until 3 or 4 hours before....NOT on arrival. TK check in may well not be open! Rock and a hard place.
