Combining meshes makes shading horrible

Development Rendering
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Left one is meshed combined in Maya Right one is parts separated
both export and import settings are identical in both cases.
Maya export settings.
Ue4 import settings
How to fix this?

https://puu.sh/qPsQY/650acd8832.jpg

http://puu.sh/qPtQW/e07a3b433e.png

http://puu.sh/qPu2m/3f1d2b977e.png