727 reving

I got a quick question for a buddy of mine. He has a 360 727 combo and tells me he car drive the car fine around town, but when he accelerates quickly the goes but won't kick down. I assume the kick down linkage, but could it be the bands in the tranny itself? I heard you can remove the linkage at the tranny and see if it shifts that way, but won't that hurt the trans with no line pressure?
Thanks