I was getting a slight vibration just off idle even standing still and I took it to a shop that works on LS motors. Rock Mountain Competitive Research said my 2008 Alpha was suffering from hardened 16 year old motor and trans mounts. They replaced all of them with the mounts from the 2008 sierra/silverado and everything fit perfectly. The driver's side metal plate unbolts from the motor mount and fits the Silverado mount fine.

I'm posting to keep people from paying $300 for mounts. The hummer mounts are solid rubber and the sierra/silverado mounts have the gel type. My truck drives fine and no more vibration.

 

Which mounts cost $300? Which mounts do not cost $300.

 

The H3 alpha mount are ~$300.

Used to be the Silverado guys swapped out their mounts for the H3 mounts because they were solid rubber and more durable/not prone to leaking like the OEM Silverado ones.

 

So the Silverado mounts are cheaper?

 

The Gel/fluid filled mounts also do not take abuse like the solid Alpha Mounts (like generated from off road obstacle flex), that is why H3s do not have pick up truck motor mounts.

You get what you pay for.