Transmission "bangs" in my 1988 chevy 1500 pickup?

I have a 1988 Chevy 1500 scottsdale pick up truck. When shifting from park to drive, park to reverse, drive to reverse, and reverse to drive, it makes a loud bang noise, and you can feel it. Once in a while it will hesitate to shift from 1st to 2nd gear. (automatic transmission) However, it has never once slipped. Is it a bad transmission? Does it need replaced, or does it just need a new gearbox or something to that effect?