Ok, so finally my left rear suspension has been fixed. The part ( A2103501753 ) cost me $30 used and labor $55 plus alignment $79. Pretty good deal for fixing a totally "loose" rear end. Now it feels good and straight.

Unfortunately there is another problem with the suspension indicating that the previous owner must have hit a pot hole pretty bad. The front caster is way off.. But this is a discussion for another thread.

Thanks everyone for all your answers.