Gradient Transperency Problem, Shader Replacement from Bumped Specular to Transperency Shader

I have a 3D object which default has "Bumped Specular " Shader and also a texture with alpha included, attached to it, but i want to apply a gradient effect on that object, so i replaced that older shader with "Transperent/Diffuse"shader but it is not interpolating from opaque to transperency correctly. As soon i replace a transperency shader the opaqueness is lost. Can anyone please tell me how can i achieve this gradient effect by replacing shader or any other method. Any shader algorithms?