99usdm gsr...

Recently i noticed some clanking noise while accelerating and engaging the clutch between shifts, thought my rear mount was shot but on further inspection i dont think so... when i put the car on stands and put the car in gear while moving the wheels back and forth with my hands, i can hear it clank kinda loud when i turn the wheel forward and backward coming from the tranny. I tested it on my h22 and it does it but not nearly as loud.

For example when taking off it sounds exactly like if your back mount was missing rubber and the motor kept torquing back and hitting metal while you were slipping the clutch to take off. It only makes these sounds while in gear. what could it be?