Did you ever figure it out? I know its been a few years now but I have the same issue and it is driving me insane. I have new struts thought that was the issue. New tires and had it realigned and it still does it. I jacked each tire up on the front and moved the tire to see if something was lose like a ball joint or upper control arm problem and nothing bad.
I keep reading stuff about transmission fluid but I can't believe that is the issue.