Alot of rear vibration at high speeds

[ReodDai]

I recently installed a prothane tranny mount and hotchkis panhard bar and LCAs. After the LCAs and panhard bar there was a little bit more vibration in the back but only over rough surfaces. After replacing my shattered tranny mount with a poly one I have massive vibration at high speeds and low speeds is enough to make the passenger seat shake no matter what. Any ideas? I'm thinking I need new shocks

[Arctc Wolf]

it's because the bushings don't soak up as much vibration as the old one's used to. new adjustable shocks would help, but they're not the reason for the vibration.

[ReodDai]

I figured the vibration would be bad but high speeds make the chassis go nuts lol. Feels like the tires are still firm on the ground just the chassis is vibrating alot.

[speedy-v6-camaro]

Could be the tires are out of balance.

[ReodDai]

Hmm thanks for that little insight there . Forgot when one of my tires blew out they put a "like" tire on the back. Its basically the same size as mine.. Its just bigger and different tread. Time for me to go talk to discount tire =).