I`d suggest changing the fluid and filter on the transmission.You can have it done or easily do it yourself.However,you must also replace the gaskets when you reapply the fluid pan.It is a messy and rather time consuming job,but it can be done in a couple hours if you have all the right tools and drain pan ect. at hand.By running it low of fluid,it likely collecting a lot of sludge in the filter.This will greatly affect it`s proper funtion.There isstill a chance you burned the tranny up,so this is just a quick fix suggestion.