Trans shifting softer after 3500 install!
You're going to be working with the valve body quite a bit ... Your aftermarket converter is physcially smaller than the stocker and doesn't move the fluid volume of the bigger one. The shift kit enlarges the feed holes in the separator plate to increase fluid circulation and makes other alterations that firm up the shifts and prolong tranny life. 


Just firm up them shifts with tuning or a shift kit(preferrable). 

