And when someone says to "run it in four wheel drive" or "lock the hubs" occasionally to keep things lubed, they're not telling you to fully lock it in. Or, if they are, they probably specify doing it in a loose traction situation or, if on the pavement, just don't do it for long.
You EITHER put it in 4wd and leave the hubs unlocked, OR lock the hubs and leave it in 2wd. That way you're turning all that stuff but not locking things together and causing a binding issue.
Same thing happens either way. Almost. Either way, you're turning some of the axle gears to spin up some lube in the diff and you're spinning the front driveshaft to keep things all nice and loosey goosey.
In adverse conditions many people just leave their hubs locked all season, or while they're in said conditions, and simply put it in and out of 4 wheel drive when needed. Saves you from having to get out to lock the hubs in the snow or driving sleet!
I do both occasionally (but at separate times of course) just for fun and to see if the hubs have gummed up or if the transfer case has somehow magically become hard to shift like so many others are.
If you needed to put it in 4wd to lube the transfer case though, we'd all have toasted cases because the rear main output bearing and shaft, which require a fair amount of lube to keep happy, would only get it in 4 wheel drive. And that wouldn't be very often for most of us.
By the same token, the front output and gears are almost always in a constant bath of lube, so they're not in any distress no matter what you do.
The intermediate gear and associated parts might benefit occasionally, perhaps, but it's probably getting a decent quantity of that stuff that's lubing the output shaft and draining back down as you drive.
Anybody with one of TOFIC's cleargearz covers verify this? Be interesting to watch video of a Dana 20's internals while driving!
Paul