The 700R4 is controlled by the TV cable that hooks to the throttle arm on the TBI unit. Other than that, there's no solenoids or modules that control shift points.
Think of the 700R4 as a TH350 with overdrive
The TV cable controls shift points and line pressure in the transmission, it probably came loose or might have broke the little clip off that holds it to the throttle arm.
It might need adjusting also, it's easy and only takes minutes.
Here's a link with instructions on how to adjust the TV cable.
TV cable adjustment instructions < click that link.