2002 Dodge Ram 1500 transmission shifts into 1st, 2nd and then nothing!!

I actually love the truck!! Its beautiful, Atlantic blue pearl coat, 4x4, Quad cab, leather interior, 4.7 liter engine, and it ran sweet until today when it felt like I hit a bump and then when I started to go it wouldn't shift pass 2nd gear, when it shifts into 3rd it won't go, its like its in neutral almost. If you gun it a little it will take off a little bit, but not very much. I just bought this Truck 3 days ago on Friday for $10,400 and I am just praying that the dealer pays for the fix.

Online it says that it is a Transmission speed sensor and its only $30 tp fix it. I sure hope so!! If anyone else has had this same problem, please email me and tell me what it cost you and what was wrong with it, Thanks,

Bought the truck with 100,000 km's. Great gas mileage ~21 mpg. Noticed that as I drive it the RPMs quickly surge up than back down. At the same time the transmission down shifts and than quickly shifts back up. No codes have ever come up. Have taken it into a reputable transmission shop, nothing wrong, doing what the computer is telling it to do. Took it to dodge dealership twice, acknowledged that something occurs, but unable to correct problem. So far spent ~$2500 on fuel pump, injector cleaning, new wiring harness, tune ups, throttle body cleaning...., still no solution.