there's a setting to turn down the crew chief (who I've heard is ben collins) and I assume that means you can turn him all the way down, though I haven't yet.
Kept somewhat low in the volume, I find it just adds to the emmersion.
He says, "okay you can do this, go ahead and go for that pass" or something... and I find myself thinking, "You know what, he's right, I can do this!" lol
but just like any game with scripted voice lines, sometimes the situation doesn't fit what he says, exactly. But not bad.