is it slipping out of 4HI into 2HI?
that link doesnt have the pics anymore, its a good fix if you want to save $$$ i just installed posilok and im not looking back. Either way works.you need to bypass the vacuum system on the frt diff.
i have run mine this way for a very long time.
here is the link for the bypass.
it is free and will take you about 30 mins of your time.
give me a call if you need to know more about it.
no the vac shouldnt hold it in place, theres something going on mechanically with your transfer case not allowing the shifter to stay in place. Im not an expert by any means with tcases but it sounds like a wear part inside the tcase has failed and needs to be replaced.How is this done? Is that what the problem is do you think. There isn't enough vacuum there to lock it into place? Sorry im really not good with transmissions and transfer cases