I have a vent from my shower that sticks up about 8 inches, can I put this between my walls and still get sufficient are flow?

It sticks up 8 inches.. above what? Sure it can run inside walls, as long as it vents out the roof the right amount for the pitch of the roof. But maybe I'm reading this wrong.

Your issue is unclear to us. Maybe a picture would help but a vent is inside the wall already if it's a vent stack. Tell us more

Are you possibly talking about an aav. If so, yes you should get enough air flow if you put it in the wall, but make sure to install an access panel to the aav, as they do tend to fail and will eventually need to be replaced.

If it is ann AAV iy can not be inside of the wall. http://www.youtube.com/watch?v=2EIjJwG-Rwo&feature=player_embedded

I think it can if it is accessible

Hi guys...

As MGD77 said, AAVS are allowed in walls as long as they are "READILY ACCESSIBLE" through a proper access panel.

In this case, I would bring the vent up to about 4 feet off the ground and then install an access panel for future AAV swap out, if needed.

Mark