1987 Chevy S-10 weird noise

I have just replaced the transmission on my s-10 from the automatic that was in it to a 4 speed everything fits right the clutch is bled and the vacume lines are connected once everything was together I tried to start the truck at which time a loud noise came from the truck it dosent happen when the motor is trying to start only when the motor starts and is running and it dose not go away all the fluids are up in both the transfer case and the transmission the sound still occurs with clutch disengaged or engaged so I know its not the throw out bering or the input shaft