Blender(part of Model) weirdly stretch out when imported to unity

I have made a simple tank model in blender and I was trying to rig the tracks by placing armature and bones then assign vertex groups /weight paint to them, and import the model to unity, the idea is to control the bones and the wheels to adjust to terrain formations through script .

in Blender I made tracks with the help of a curve modifier and the track is a one solid object, the bones are all under one armature in the hierarchy, I assigned the tracks to the Bones.
Problem when I import the model to blender the tracks stretch out in some weird way I have spent a week searching and fiddling with it to fix it but I failed .
here is a link to the model
https://www.dropbox.com/s/06z341mif64i0cu/TModel.blend?dl=0
I can upload the c# script as well if needed
I will appreciate any help

 

It looks like a new secret weapon

Are there some scaling issues? What happens if you move the parts manually in editor instead of letting the animation do it?

 

Yeah it does indeed lol

No animation involved its simply the bones attached to the tracks with weights allocated

 

Definitely Apply all the scales in Blender so everything is 1.0 scale in all directions. Applying rotation would not hurt in most cases too.