F250 4 wheel drive inop
 

Wow, it has been a while since I was last on this forum. I received my "Happy Birthday" greeting yesterday and thought I would drop in ask a question and start following the forum again. I hope everyone is well and the new year has begun well for everyone.

So, I am having trouble with my 1999 F250, 7.3, 4 wheel drive not engaging. When the switch is turned neither Hi nor Lo indicator lights come on and the hubs do not lock (nor can the hubs be locked (can't be turned at all) manually). The vacuum system is operative and the vacuum hose have been changed (routine maintenance item). The relays appear to be working well and fuses check out. Any thoughts or ideas?

Thanks,
Scott

ps: thank you for the the birthday greeting, it brought this forum back to my attention.