...when the rear suspension is loaded. It happens pretty often when the whole car goes over bumps or dips, usually as the rear comes down through a dip in the road. It will happen when turning as well. Could this be the torque arm or some other mount? It feels like it's right under me sometimes, or a little behind me.

 

yeah i would definitely look at the torque arm mount then.

that would be alittle further back then the tranny mount, and since u have a poly tranny mount, unless its lose for some reason its most likely the torque arm mount.