Transmission rattle in 3rd gear?

[Kamillio]

Yesterday I drove about 150 miles to visit a friend and do some spirited driving in my 2014 NISMO.

While in the back roads, I kept the car above 3000rpm but below 6500rpm most of the time and shifting a bunch around some tights turn. After about 10 mins or so of driving like that I went into 3rd gear accelerating and as soon as I passed the 5000 rpm mark something in the area where passengers left foot would be located started making this loud chatter noise and the stick shift started vibrating as well. I assume it was coming from the transmission.

As soon as that happened I backed of the throttle and as soon as it went below 5k rpm it stopped, and I tried replicating it and it would do it again exactly above 5k rpm. It would never do it in 1st, 2nd or 4th, only in 3rd above 5k rpm. At the time the oil temp was about 240F and it was 90F outside. I got scared so I finished the fun for the day. I know it never did that before because on highway ramps I go in 3rd above 5k rpm many times.

Later I drove home 150 miles again, having fun while driving, accelerating and decelerating a lot throughout the whole time and the car was acting normal (don't think I went in 3rd gear above 5k rpm, but did try almost every other gear above 5k, except the 6th one ).

Has anyone had this happen before? Any tips? I would I appreciate any input from your knowledge and experiences!