I smell gear oil`

Transfer case most likely or transmission. Both are "vented" up through the shift lever and if the wind and driving speed is just right, I always get a whiff of the stuff. That is one reason I run Redline synthetic gear oil in my tranny and transfer case, its a whole lot more tolerable to breathe than regular gear oil:

A vent lets the hot air and oil fumes escape from the gear box when it gets hot under load. Then, as it cools, outside air is allowed to re-enter the gear box to equalize the pressure.

Its normal venting most likely, oil is getting hot, fumes come out the shift lever and if the wind is blowing just right, it'll come up into the cab. Check that shifter boots are tight and intact. You may even consider adding a real vent and route the fumes via a hose out to the engine compartment, that is my plan.

Pull the fill plug (on the side of the tranny by the revers light switch/wire, on the back of the transfer case) and check the level. Oil runs out = over full, oil just at the level of the hole = proper fill, oil below the fill hole = low oil.

I too had the same problem. I could smell gear oil but nothing on the rear-end...it was dry. Turned out to be the pinion seal was leaking...the rotation of the driveshaft was sending the oil onto the muffler...yet no drops on the ground. It was puzzling at first trying to find the leak and the smell.

Dan