NOISE COMING FROM UNDER MY 96 ECLIPSE GSX I THINK IS THE ONLY WHEN IM IN GEAR?

THERE IS A NOISE COMING FROM UNDER MY CAR I THINK IS THE BUT NOT SURE IT GOES ...CLACK CLACK CLACK EVERY TIME IM IN GEAR ..I PUT IT IN NEUTRAL AND IT GOES AWAY I JUST GOT THE CAR A WEEK AGO NOT SURE WHAT IT IS PLEASE HELP !!!!!!!!!!!!!!!!!! CAR HAS 100K IT ALSO SLIPS FROM FIRST TO NEUTRAL I HAVE TO HOLD IT IN FIRST IN ORDER TO GO SO IT DOES NT SLIP