95 lumina trans/speedo question?

ive got a 1995 chevy lumina car, with a 3.1L and a overdrive trans, the cars got 220,000 on it the motor has been changed once the trans twice , the newest trans is out of a flipped car that only had 80,000 on it, and the trans has a GM Goodwrench factory rebuild sticker on it, so i was sure it wasnt whipped, anyway, ive had to replace the vehicle speed sensor before, cause it was making the speedo act up, it would bounce around on the highway, and not work at all at low speeds, the car drives but will not shift right, and from a stop is like driving almost with your foot on a clutch, no low speed power, turn it offf and restart it its fine, till it goes fast, i need to know what in side the trans runs the speed sensor, i think its the culprit, or any other ideas why the speedo quit, its my beater im not going to rebuild it or pull the trans or anything, hopefully its something stupid,, please help