2nd 3rd shift could very well be a symptom, but not the only symptom. If this is the only issue the transmission has, it is probily an isolated issue...ie. band, servo, intermediate clutches worn, etc...but the valve body is a "brain" for the system. The automatic transmission is nothing but a hydraulic drum which depends on hydraulic pressures as well as centrifugal forces. If there is a valve body issue, there would be several symptoms. If I can help more, please feel free to put the issue out there and I will surely do my best.