I tired to drive my SRT all the way up to its rated top speed limit on Saturday, but for some reason it wouldn’t exceed 115 mph. I had it for awhile in 4th gear speeding at 100 mph and watched the tachometer rev up to and remain at 6000 rpm. A few seconds later, I decided to shift the gear into ‘D’ drive, but there was no noticeable change in speed, even after maintaining the speed of car at 6000 rpm. What is wrong with my car? What am I doing wrong?