2002 Pontiac Bonneville Transmission out? or is it electrical?

I still have 1st and 2nd gear and also reverse. But 3rd and Drive do not work at all . I just hooked back up the dash board that was unhooked for some reason. So I left the driveway and put it in drive after backing up and it felt like it went into drive and it did I gave it gas and it started to go then all of the sudden it made a loud clunk, Jar sound and no MORE drive or 3rd gear. But when I drove it around the block in second gear it was almost like something was holding it back from going any faster .... Could it be an electrical problem of some kind ? And maybe not mechanical ??