trans swap

hello, new here....bought a 85' Buick Regal 3.8 4 barrel. Get the car up and running only to find out it has a bad trans. If you put the car in drive the trans starts to chatter and bang when it shifts. If you put in 1st and change the gears manually it'll act fine. Not sure what's going on with...

I have a 1987 Monte LS. It was a 305 4bbl car with a 200r4 trans. About 10 years (and only 5000 miles) ago I swapped the 305 out for a 355 and went off the computer and emissions stuff (Edelbrock intake, cam 1406 carb) and went with a TH350 trans. I recently got a 3:73 posi unit out of a MCSS...