I can't say why the gear oil would have that odor but I agreee that your rear sliding window is why you were smelling it. I don't have the opening ...

I can't say why the gear oil would have that odor but I agreee that your rear sliding window is why you were smelling it. I don't have the opening rear window on this truck, but have had it on most all of the ones in the past. I noticed that when I did have them open, it seemed to create a condition where it pulled dust, odors, and stuff into the cab. That is probably why your were smelling it so strongly. Now that you have re-routed the breather tube, hopefully it won't be a problem for you. You have a long miles/time powertrain warranty. If anything were to happen, you will be covered. But, I understand, it would bug me too. Hope you get it figured out.

OK I pulled the trailer again this weekend. I now have over 4000 miles on the truck. It pulled pretty much the same and you could faintly smell the axle vent with the window open. Moving the position to behiend the tail light definetely helped with the stink. I measured the dif temp after about a 80 mile (Hour and 1/2) tow. The ambient air temp was in upper 70's. The dif cover measured 216 degrees and the dif housing was 226. This seems pretty hot to me but I don't know what the normal operating range is. I have a call into the dealer again.
JJ

can you smell it when you get out of your truck? 226 isn't hot enough to burn the oil. I do think that you will be using your 5year 100,000 warranty on that axle. or bug the service manger until they replace it.