Automatic 4×4 hub issues

[g-man]

I am having what is going to be major issues w my 4WD! About 3 years ago the automatic hubs were replaced and for some stupid reason I opted out of the more reliable manual hub set up and went with super expencive factory auto hubs. Worked great for a few winters and light off road 4wd use. Then one day out of blue, out of 4wd, it made this high pitch whining sound followed by a HUGE thud!!! And going about 45 mph it felt like the whole front end fell out! It does this on occasion now however when i turn sharp you hear a ticking sound...heavy bad gear mesh ticking followed by a heavy loud thump when you straighten out. Wtf? Im going to dive in it today and get a look see. Dont have the $ for a major shop bill...like alot of us hard working americans! Q: do these auto hubs run on a vacuum assist? Had a s-10 long ago that did. Any help would be appreciated! Thanks!

Sent from my DROID BIONIC using FRF App