The MP chassis book refers to a "boom" sound if overtorqued...But at the other end of the equasion I've found that just torquing the U bolts one time led to a "boom" of it's own..The rear housing and the leafspring separating under the launch...Now I retorque them a few times after some miles on the vehicle... Just like a wheel...

The squeak is a tough one could be dry bushings as stated or the leaf interliners wearing in..Spray them if it gets too annoying..