2k ES. car seems to shift fine and goes into reverse fine on level ground. i noticed when the car is pointed downhill that it will snap into reverse with a bang. checked fluid. level is right on. i live on a fairly steep hill. i overshot my driveway by 10ft or so and stopped car and put it into reverse and "bang" it went into gear with a thud. almost like the torque convertor was freewheeling. on level ground it goes into reverse with no fuss. any ideas?

 

could be a CV joint and you just notice it downhill right now. might just be starting to go and not quite gone right now.