91 Nissan Pickup truck4x4 king

It is a 4 cylinder and my question is on the transmission cross members there are two weights on it that just bolt up What are they there for? And my second question is that when I let off the clutch in first it gerks for a little while and it continues to gerk until you get speed built up in 3rd or 4th gear could it be the pressure plate or is it possible that it could be the motor mount because it feels like a dry foam instead of a hard rubber(dont know if this is normal)?