Did i damage my 727

Okay guys well got everything back together cable transmission pan and shifter and minor things. Well I went to take it for a test drive today and it seems fine until it shift into 3rd and I hear and feel almost like a clunk and then it just vibrates alot and gets worse with speed, does this mean that possibly my 3rd gear is messed up or what could cause that? Driveshaft new rear end has been gone through and it seems to be coming from the transmission I feel, it so bad it shakes the steering wheel is messed up from this or idk where to go from here