Hello all. I have an issue that is developing with my Tahoe.

Stats:

2004 Tahoe, 5.3 litre Vortex engine, 123,000 miles.

I have been hearing a valve tick lately coming from the drivers side rear of the engine. I need to know if anyone has had any experience with this and what it could be? I will be giving it to my mechanic next week to diagnose but want some opinions on what it could be so I won't go in to see him blind.

Thanks in advance.