99 GV 4wd transmission issues

[dafyd69]

Hi, I have a 99 Grand Vitara (standard) that has been in storage for the last number of months (I have been overseas). When I tried engaging the 4wd I get nothing. If I try to engage it while driving I can hear a high whiring sound. Before making the trip to the dealership and getting a second mortgage I was wondering if anyone has any suggestions.
Is it likely that this is the air pump? Or is there an electronic component that may not be allowing engagement? Or perhaps something else.

These are auto hubs.

Any help would be greatly appreciated as the weather is really not as inviting for non 4wd lately.

Thanks