I have a 93 grand prix se and the transmission started not shifting, took it to shop they put in one from a junk yard. It wont shift. Got another one it wont shift. Took it to the junk yard shop the put in one and it wont shift, its like starting in maybe 2nd gear not ****ing up to OD and wont down shift, they tried a scann nothing. They have checked fuses and wires nothing. This problem started when it wouldnt down shift if it did it was rough and then it wouldnt take off,, sometimes cut off. There was a knocking noise in front part of transmission when you start the car and let it sit so we got another trans, its been in this shop 2 weeks now and they still dont no anything. Anyone have a clue??