Need help with shader

[AlvarezLynx]

Hello all. I just wanted to ask that like dif.spec.a draws light and shadow accordingly in game, why doesn't dif.spec.over do the same?
I mean I used dif.spec.over shader but it doesn't have any effect of light and shadows, just it keeps bright even when I drive my truck under shadow.
Why is that? Is it a game limitation or am I doing something wrong?
My shader settings for dif.spec.over are below:
Diffuse : 1.0,1.0,1.0 (R,G,B)
Specular : 0,0,0 (R,G,B)
Shininess : 4
Add Ambient : 0
Reflection : 0
If anybody can explain, It will be helpful
Thanks in advance

[all_zer]

As i understaind,
dif - is basic texture
dif.pcec - adding special lighting on alpha-chanel on textures

checkbox over is overlaying 2-nd image over 1-st. like in photoshop with layers. (blending mode -> overlay dark or light. depends from alpha chanel)

In my way, i always use the basic - dif without spec and all others... works great.
specular - is shining color. in which color you want to have shining
shiniess - is radius of shining point.
0 - all texture will be shining all time
10 - big poing of sun reflection
take 100 and more, if you wont to have smal point of sun reflection (like in real world at glass)