mcb3211

I have a 1990 Integra 1.8L w/ automatic trans.
When it is about to shift from 2nd to 3rd the engine revs up an additional 1-2k then it goes into 3rd gear. The rev only last for about 1 second...it shifts very smoothly into third gear..4th gear is fine its just going into 3rd that it does this reving. also the spedo kinda "bobs" around a bit the whole time I am driving...any suggestions...could it be the speed sensor??
any one know where the speed sensor is located.