Connected Rigidbody2D with HingeJoint2D not working properly

In Unity4 I had a RigidBody2D connected to my player Rigidbody2D using a HingeJoint2D.

When my player is hit I remove the Joint and the second Rigidbody just fly away with the momentum of the Player's movement.

Now after updating to Unity5 the second Rigidbody has no momentum at all. Once the HingeJoint is removed stays exactly in the same position. And while connected to the player it feels weird, like it's draggin something far more heavy than it really is.

I haven't changed any code at all so I wanted to know if this is caused to some new feature or if it could be some kind of bug.