Something to keep in mind, is that the rev limiter chips will usually come in about 200rpms sooner than the advertised, so that your 6200 would have been about 6000.
When I do the math for the MPH, gear, and tire size it shows that 117 mph would need about 5600rpms without slippage. With the limit most likely hitting at 6000rpm's that shows that you have only about 400 rpm's of slippage on the top end, so it doesn't appear that you have a problem with either your transmission or your torque converter slipping. When you go up about 200 rpm's more, it shows that you would only reach about 122mph (the same as if you kept the rpm's the same and changed the gear to 3.73). If you changed your rear tires to a 29" tall, then you would be about 128mph with the rev limit up to the 6400.
Right now your effective gear ratio is like a 4.56 with 32" tall rear slicks.
Bill