I'd like to keep the Suregrip, and I think I'll try the oil change. TheChris -- I'm not there, so I can't listen to the car to be sure, but you may want to confirm that the noise is indeed coming from the rear end and not from the axle bearings. On THREE of my Imperials, each time I've started go get a noise from the rear of the car, the problem has been axle bearings.
Chrysler manual emphasizes this, so I think it's worth a try.
I think the BIGGEST challenge for all of us is finding someone we can TRUST to steer us in the right direction.