Automatic 4th gear wouldn't engage

[napkinthief]

I was crusing along and just testing my brakes which are now grinding metal and decided to take it up a bit and see how long it takes me to stop. In my 3rd gear i topped off at 70-72 and rpms where 7.5+ I started freaking out and the car was jumping like when you rev in neutral and hold it. I pulled over and restarted the car and the problem went away, is this anything serious? I have a drivetrain warranty that should cover it, but wont cover checkups or inspections.

 

[Defiant]

I was crusing along and just testing my brakes which are now grinding metal and decided to take it up a bit and see how long it takes me to stop.

WTF