my brand new 2014 3500 diesel is broke down after 300 mi they say its a mother board and its gonna take 10 days to get has anyone ever heard of such a thing?

Well the good of this is that it,s under warranty,next thing i would say,it being that new,is what other future problem,s will come after this?

And know it should not take this long to get or repair,i think there still scraching there head at this problem.

I agree with tennis shoes since it is new. I've had 5 new Dodge w/Cummins since 95'. Never had a problem. But, protect yourself, I would check all new vehicle laws (lemon) in your state. Consult w/Better Business Bureau, business's don't like complaints filed, but it can help negotiations in case of settlement needed. Keep copies of all work done on the truck. Document what was said and when.