wierd groaning noise when trying to downshift

[87gninpa]

When cruising at about 45-50(converter locked) and i give it a littel gas to try and get going(not a full on stomp of the throttle) the car just groans until i let off the gas. i think its a transmission noise as its coming from right under me, could it be the converter going bad? im not too experienced with transmissions, so any opinions will be greatly appreciated TIA