MYTURBOT/A

Help me out here guys Just recently I started getting a clucking noise in my drivetrain like when you have a bad u-joint it`s repeated and speeds up as you accelerate like a u-joint. But it only does this under extreme torque like when the tires are on the edge of spining and grabing. I`ve checked the rear suspension everything feels tight both u-joints are new and tight torque arm is in one piece and the mounts look good.but the sound is definitly coming from the rear area of the car. has anyone had this problem or any suggestions on what to check? thanks.