At the time i bought my yukon I found some thing according to my experience it is a defect, if u set in the driver seat, with engine runing at idle speed, move the gear shifting leaver from R to D and D to R, u will hear clinging soung in the transmission, this sound due to a back lash in the gears of the transmission or the difrential, I tested other yuokon and tahoe and found same sound, the dealer said its normal but I dont think so.