Fortunately, everything was moving at the same speed. It was only last night after it cooled off and the slush turned into ice I switched on the 4wd and got rwd only.

This morning I manually engaged and disengaged the the hubs then cycled the switch on the dash and can clearly hear the audible click as it's trying to engage the esof.

There was no ice today so I left it in2wd. If I get out again tonight I'll try the esof switch and see if it engages now that I've manually cycled the hubs and hopefully loosened up something that was binding it.

I replaced the vacuum hub lines with stainless steel braided lines about 2 years ago to avoid the problems with vacuum leaks from old brittle hoses.

If I do need a new PVH I've got the link to Tousley/AutoNation saved...