1997 Z34. 4t65e PCS?

I have a 1997 monte carlo z34 with the 4t65e transmission. 39,000 miles. Lately it has been shuttering bad at the top of 1st gear under hard acceleration. It also takes longer than normal to engage when I shift from part to drive or reverse to drive. Could this be my Pressure control solenoid? I hear alot about harsh shifts and wining when they go bad. I have the wining, its very audible, but the car shifts just fine while driving.

A full scan with a trans function scanner can look at pending trans codes and solenoid functions.