Purpose of center diff mounting plate?

[MetalMan]

Like Sylvester said, these pieces add rigidity to the center diff area. If you have an integrated motor/center diff mount (the center diff and motor mount to the same piece), then the upper plate is necessary to help hold in holding the weight of the motor.

I also like to use this piece to mount my ESC to, since it's out of the way and the ESC gets a lot of cooling when it's there.