On cold days and first start up of the day my 06 Trail blazer has a bad vibration it goes away when i put the truck into neutral only any other gear it gets worse or stays the same. I think its somthing thing in the tranny but looked and the mount and nothing seems wrong. please help. It the I-6 engine

Sounds like a classic motor mount / tranny mount issue. Most of the time it will be the motor mount though. The mounts may look ok but they compress over time and they need to keep the motor up higher than it is. Go with OEM mounts (as aftermarkets tend to be too soft and you'll end up having the same problem quickly) , their around $100 each, but a PIA to change.