krow

My trasmission just started to make this noise that sounds like my rods or lifters are knocking. I don't have 1,2,3,5, or reverse, but I still have 4th gear. I was just driving and when I shifted into 2nd gear and it made a loud crack noise, and then I didn't have 1,2,3,5, and it sounded like I blew the motor, but when I push in the clutch it stops. What could that be? PLEASE HELP!