no oil or grease to replace....unless you loosen pinion nut....but, if you do not loosen front pinion nut it is easy and doesn't take long...only rear front drive shaft bolts are a real biyatch to get off...be real careful not to damage the flange..but a flat screwdriver and hammer/mallet does the job...just be persistant..

have to shift in and out of 4 low and neutral to move and lock drive shaft where needed to loosen bolts...