Down shift going down the highway
 

As i was going down the highway my xg300 jerked hard on me rpm's went way up. Put it on my slap **** and saw it was in 3rd gear and would not shift up. After stopping and turning the car off i had no more poblems. This has happened a few times now. Also have had problems at starting car at times where it runs high rpms and when i push on break to put into gear the car dies. Would these be tps poblems or speed sensor issues?