Ok, thanks for responding. It's a '09 with a V8. The truck has a 90 day warranty and the used car's repair shop says it's a pinion bearing. The probability of them getting the repair right, prompted to try and find another entire rear. Could anyone explain where to find the serial # for the present rear. Have a feeling that the factory may have stuck a 8.0 rg as it was the end of the production run, build on 12/08.