I heard a clunking noise from the back of my 05 MCS that only happened when turning left, after much searching I've narrowed it down to 2 possible causes. The right side bottom control arm has a fair bit of play where it attaches to the swing arm, and, same side there is a bit of movement at the top of the shock where it attaches to the frame. My question is this: to replace the control arm do I have to do both upper and lower arms, is it as easy as taking the bolts off and replacing?

 

You dont have to replace both the upper and lower arms, if you need you can just replace the lowers. It is as easy as taking out the bolts and replacing the arm. Maybe you could retorque things and your problem may go away. My end links are constantly needing to be retorque'd even with loctite on the threads.

 

Do I have to replace them in pairs, the left side is still pretty solid, or can I just replace the worn one? I don't think that torquing the arm would take the play out, that being said, what should they be torqued at?

 

I highly suggest getting the new bushings for the rear trailing arms, and do them in a pair. An alignment afterwards is also necessary. Check the gap between the front side and rear side of the rear tires to the fender trim. If they are not fairly even or pushed back then the bushings are shot.