2013 Nissan Sentra fuel system problems

I purchased the vehicle in april. Two months later I realized that when in drive when I set my foot on the brake I would hear a grinding noise in the back of the car. When I would put it in reverse the noise would not occur. It was always when I would hit the breaks until the car came to a complete stop. It would not make the noise when I hit the breaks suddenly. When I called nissan and brought it in for them I was told that it was a fluid problem.

I bought my 2013 nissan sentra sr from towne auto brokers 03/2013 I test drove it and it had no shifting problems at that time. 2 weeks later while I'm driving it the sentra started jerking and idling erratically, the RPM tachometer red lined 3 times without the gas pedal being depressed!! While redlining the sentra's transmission shudder with the erratic jerking all the while decelerating before catching 3rd gear at 4,000 RPM. I was in rush hour traffic 3 miles from home so I decided to try and making it home.