stripped spline and damaged power output shaft front differential

While driving on highway, stopped at a light, I went to accelerate and truck lurched forward, made a loud bang and would not engage. The engine whines when accelerator is pressed, but no movement. Also, vehicle would roll back without the emergency brake on. There were ZERO warnings prior to complete failure of truck. Contacted GM and Chevy, and was offered NO help, until out of pocket diagnostics are completed at a GM/Chevy dealer (and at this point since vehicle is out of warranty, owner was told that help from GM is not guaranteed). Truck is at a private shop, preliminary findings are that the front differential is damaged. The power output shaft and spline is stripped, the cause is vehicle (drivetrain) design does not allow engine oil to get to these components. The parts become dry and brittle, which is why the gears are stripped and failure occurred. This is not an owner maintenance issue, but a complete design flaw. These components should be encased and be getting lubricated from the engine oil. Owner will be in contact with GM after all findings are complete and damage is fully assessed.