If you ever hit that kind of RPMs in first then there is an issue with your second gear not engaging properly. Stock transmission tomos usually shift into second at about 15 to 20mph which is right around 5k. You can get them to stall longer with a stronger 2nd gear spring but still not up to 10k. That would do unhappy things to the transmission.
If you opened up the transmission and didn't see chunks of metal, broken bits of a part or any damaged gears then it is probably fine overall.