Hey Scotty. 2004 GMC Yukon. Changed rear rotors and break pads and bled system to replace brake fluid. Now on initial breaking i have squeeling until I break a bit harder and it goes away. I did not change out the clips or grease the pads where they go in. Could that be the issue. I was in a hurry and now I regret it....

yes, that could be the problem, but also clean the rotors with spray brake cleaner too as any grease or anti rust coating on the rotors can do that too