Clutch not locked but not slipping??

[NewLife]

hello,
i was trying to understand vdrift clutch implementation and im facing something that i cant understand.
Basically in vdrift the clutch is considered locked when:

Code:

if (friction_torque > max_torque)                    // slipping clutch
{
    friction_torque = max_torque;
    locked = false;
}

Since:

Code:

btScalar torque_capacity = sliding_friction * max_pressure * area * radius; // constant
btScalar max_torque = clutch_position * torque_capacity;
btScalar friction_torque = max_torque * new_speed_diff;    // highly viscous coupling (locked clutch)

we can write:

Code:

if (clutch_position * torque_capacity * new_speed_diff > clutch_position * torque_capacity)     // slipping clutch
{
    friction_torque = max_torque;
    locked = false;
}

simplifying:

Code:

if (new_speed_diff > 1)     // slipping clutch
{
    friction_torque = max_torque;
    locked = false;
}

So when the engine angular velo and the clutch angular velo differs more than unit, the clutch is considered slipping.
But, if you run vdrift in debug mode, you can see clearly that in almost any situations in which the clutch behaves like locked (normal driving, especially in lower gears) the angular velo delta is more than one unit.
How is this handled?