[Christ]

It's not fine with all transmissions, it can still be damaging, depending on which shaft is immersed in oil.

As long as the output shaft of the transmission is the one that's slinging lube all over, or if it's a pressurized oiling system, with either an electronic pump, or a output-side pump, you're fine.

If you're unlucky enough to have a tranny w/ the input shaft slinging oil, you're probably still good for awhile, since it's just gear friction you're worrying about... The viscosity of the oil will make it hang out for a good while before it actually needs to be exchanged for fresh oil to cool and lube the bearings/gear faces, but there are claims out there that it can damage your transmission if you have an input-fed oil system, in a manual transmission.

If you have a shift on the fly 4wd system, put the xfer case in neutral, not the transmission. Just about all vehicles with SOTF 4WD can be flat towed as long as you shift the xfer case into neutral. While the xfer case is in neutral, the transmission can be put in any gear there is, since no part of it is moving anymore.

This won't work on older stick-shift xfer cases, though, as they're not even close to synchronized, and won't go back out of neutral until you come to a complete stop. (Unless you're really good at gear/speed matching.)