dull thump thump or clunk noise heard

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i hear a dull thump thump or almost a clunk or low tone pop noise while shifting through the gears.it kinda reminds me of the sound of a bad engine mount.like the engine is slightly lifting as the torque is applied through acceleration,then when clutch pedals depressed the torques gone and lets motor drop back down.it kinda feels like it may be inside trans though.could something in clutch assembly make this noise.