Vibration/thumping noise

Good morning everyone, I recently changed out my rear differential mounts on my MS6 with the upgraded ones from cork sport and sure juggernaut front diff mount. After that I heard an audible and vibration at the rear section of my car almost like a thumping noise, almost like the rear diff is engaging and disengaging. It’s felt at cruising speeds of 50 mph and more; I’m assuming it’s the rear axles causing this issue. What is your experience with this? Also where can I find replacements for the rear axles, I only see the DSS upgrade ones, or am I screwed with that selection.

 

It's widely known they will have more noise from them. But vibrations not sure. Alignment and wheel balance are the 1st items on my list of starting simple.