Cougar loud Knock when first starting HARD in Forward/Reverse

2000 cougar ok when u go forward or reverse slowly and build up slowly its fine but when u go forward or reverse hard u hear a loud knock just once then if u stay in that direction you're fine even if you come to complete stop then go hard in that same direction. but again if you go in opposite direction BANG. so im thinking is the mounts but...... i saw some shiny newly exsposed metal on the left tranny mount and if you check it out in the opposite direction then when u first looked at its covered alittle so it is moving i think..... but i tightened it and it still didnt help u still get the banging sound! any ideas???? could it be vertical movment, the bolts holding the mounts to the engine??? and not bolts holding mounts to chassis?????? PLEASE HELP
ps dont think its the gears cuz after the sound you can drive/shift fine in same direction without it happening again