Various ZF documents on the ZF pocket bearing failures. Here is one that mentions incorrect lubricant as a possible cause of bearing failure, though there are more specific ones (http://www.zf.com/na/content/media/u...g_ZF_S5-47.pdf
). Also here is a picture of a ZF input shaft failure, note the gear oil in the picture, not ATF. May have been contributing factor.
I also build engines and transmissions. Common knowledge, with tight tolerances if you run too thick of an oil (i.e. gear oil in a ZF5 made for ATF), oil will not get everywhere it needs to since tolerances are tighter. The resulting lack of lubrication rapidly accelerated wear and parts break.
Conversely in a rear axle if you run too light of an oil it'll get slung off the gears and bearings and not be carried to where it needs to be. ATF is not thick enough to walk on the gears and be carried where it needs to be, resulting in insufficient lubrication especially in hard to get to areas such as the pinion bearing. Result is a dry pinion bearing that wears rapidly and fails from insufficient lubrication.
ATF and 30w are not far off, and there are guys that run 20w or 30w in their automatic transmissions. It's a different type of application than a vdrive. a vdrive is more similar to a rear axle and typicaly runs either gear oil or motor oil, not ATF. Maybe the new vdrives are different, like some of the newer transmissions, I don't know. I'm just advising what I know about transmissions, axles, and lubrication in general. Stick with what's recommended by the manufacturer unless you built the unit and know the clearances and lubrication path.