I think you are probably right with what you say. Thank you for filling in the blanks and giving us more information to work with.
Here’s my feeling (I used to have the same problem):
Your lower traps are not as strong as the need to be to hold your scapula in place during a pull-up OR you are not setting them complete at the start of the movement so your shoulder is able to float up during the movement OR the lower trap fibers are not firing correctly to pull the scapula back and down.
Prone incline Y raises or t3 raises will help to develop the strength of the lower traps, as will hanging scapular rotations (hanging from a chin bar and pulling your shoulders back and down) and T raises to a lesser degree.
It’s an easy fix regardless of the cause. Just do more work for the lower traps. Consider even starting off your back workout with something that will activate the lower traps. Once they get stronger and are able to hold the scapula in place the issue will be resolved.
One other thing that may be is to make the pull-up to distinct movements, the first is the scapula setting and the second in the pull-up portion.[/quote]
Thanks for the advise, really appreciate it.
Any chance you, or someone else with the knowledge, could explain what “Prone incline Y raises or t3 raises” are? I’m still enough of a newb not to know. I wish T-Nation would work on an exercise database, it would really help the beginners out a bit. I end up using the bodybuilding.com one, but the ones you listed don’t show up, at least not under those names.