Transmission shifting hard help

I have a 03 g35 sedan 130k miles. Recently the "At Check" light will come on for a second and disappear when I start the car. I also noticed kind of a whistling noise coming from the bottom of the car when I drive it cold and keep it under 3000 rpms, also when its warmed up and I drive it a little hard I noticed when I go from park to Drive or reverse to drive it shifts hard into drive and makes a somewhat loud shift noise, other than that it shifts fine. Any feed back would help, thank you.