Well I had a nasty creak/groan from the left rear suspension when I bought my Bonneville. I have not done anything but my wife finally put her foot down since the car makes a terrible groan from the left rear when she gets out. She said it makes her feel like she weighs 500lbs (she is only 150lbs).

So I put the car up in the air a week ago and lubed everything in the rear suspension that moves. I filled all the joints that had grease fittings and then sprayed white lithium as best I could on all the rest of the joints. Where the springs touch the upper and lower spring perches I also sprayed white lithium grease.

I don't know which thing took care of the noise since I did them all at once. Regardless of which one was the problem I am very happy the noise is gone and my wife is happy.