Car hesuitates like it's out of gear on acceleration and then takes off rapidly. Seems to be worse after it warms up. Freeway driving is fine, only happens in first gear. Engine appears to be running fine, it's a transmission issue. Not slipping, more like freewheeling in neutral and then slamming it into gear. Anyone had this problem before? Any advice on what to do or where to start on troubleshooting. Car has about 60k miles.