Hello Everyone,

I have a really odd thing happening to me intermittently. Its been pretty cold up here in Canada (-25 to -30 degrees C) lately and this problem only seems to occur when the truck is cold on the first drive of the morning. It has happened about five times now and I have taken it to the dealer but of course the problem couldn't be reproduced. When in 2wd after a very short drive (a few 100 feet or so) I'm getting a loud bang out of the front axle area. It almost seems like one of the hubs is trying to engage but no switching into 4wd is occurring. Is this possible? Can the electronic vacuum valve possibly be failing and switching automatically without selecting 4wd? Or could it be another issue. 4wd seems to work just fine when selected and the dealer said the vacuum operated hubs are working correctly. Any other ideas would be greatly appreciated!

Thank You