It has been said that the fron diff isn't really turning much when not in 4x4, so how can it be broken in like the rear? I would think it would need some miles to break in like the rear, but it's not good to run in 4x4 on dry or even wet pavement, and it's kinda hard to do a lot of miles on the beach...

Just click it in once and a while while going straight down road at city speeds. You'll be fine.

The front axle is always turning regardless of whether you are in 4wd or not. Since the axle is always turning while you are in 2wd, all your bearings and the "coast" side of the ring and pinion teeth are being broken in whenever you are in motionhttp://www.dieselplace.com/forum/smileys/Geek.gif.

the ring and pinion should not be turning or if it is, it is not doing so with any type of a load. The left axle just goes through the spider gears and gets unloaded there, the right side is mechanically disconnected from the spider gears

I see your point. The spiders won't be turning while both left and right wheels are rotating at the same speed. In a turn situation the spiders will be turning. The diff side bearings will be turning all the time when the truck's in motion.


I always change front and rear diffs together when mileage indicates a lube change.