Cruise Control Issue Help!

Took my 06 double cab limited on the highway yesterday and threw her on cruise. After about a minute of normal driving set at 75 mph, my rpms spiked violently and my tranny upshifted rapidly. Disengaged the cruise control and truck was fine. Put her back on Cruise at 70 mph and same thing, drove fine for maybe a minute then felt like the truck was violently trying to accelerate. The vehicle speed did remain locked at what I set the cruise to though. Anyone else ever had this issue? I am driving from Wisconsin to SC next month and cruise control would be nice to have. I looked on Identifix through my work and found a similar occurrence listed with the codes P0500 and P0503 which reference vehicle speed sensor malfunction though my truck has no stored codes so I'm not sure if that is it. Where is the vehicle speed sensor? I am assuming it is on the tranny somewhere or are they referring to the abs sensors? Any help wold be much appreciated!

 

I had a 2007 4.6 double cab that would do that at locked in speed when traveling up-hill. It didn't take much of an incline to downshift even without towing.
I had the vehicle for eleven years without any issues so I'd say it' normal and nothing to worry about.

 

I was on a pretty even stretch of highway when this happened. I thought that might be the case too but this really felt violent and not like it was supposed to do this. I cant imagine Toyota would design their cruise control to rev that high with regular highway driving set at 70 mph. Maybe whatever senses the vehicles incline is messed up on my truck so it thinks I'm going up hill? Thank you for your input.