About the driveline basics...

[joevenzon]

No, the speeds aren't equal. I repeat: the crankshaft speed is based on the engine RPM and transmission, the driveshaft speed is based on the wheels' RPM and diff.

The clutch takes those two speeds and generates equal and opposite forces on both the engine and driveshaft. Force = mass * acceleration, which means acceleration = force/mass, so the rotational acceleration of the engine and driveshaft will change. That means that with the clutch (even partially) engaged, the speed of the engine and driveshaft will tend toward each other over time, depending any other forces acting on the wheels or engine.