You mean a wet, oily stain behind the rear-most driveshaft yoke at the front of the rear diff housing is a problem? Not according to my "5-Star" dealer's service dept. I have had the stain similar to the pic above since the truck had a few thousand on it (it has 9k+ now). I've asked the dealer to look at the "leaking pinion seal" at the last two oil changes (i. e. , one @5k mi. and one yesterday @ 9k mi. ). The dealer swears it's the draft tube blowing oil all over everything under the truck. I will admit you can see the splattering under the truck, including on the diff (my driveway has black oil spots on it for the draft tube dripping oil). It is, however, impossible IMHO that the draft tube is splattering behind the yoke and the shield at the pinion seal. Yesterday, the dealer swore they had three techs look at it, but they swear it's dry at the pinion seal, so it "must be' the draft tube spraying everything. At this point, if they're not gonna change the pinion seal, at least I have it documented so I have recourse under the lemon law in case I get screwed later with a shot diff.