2000 Ranger 4x4 Loud Clunk

Hi!

New here and this seems this topic has been addressed here before yet the solution seems a bit vague. It seems this is a common issue with 4x4 Rangers.

If you watch this video link that I found it's exactly the issue that I am having. No need to watch the entire thing other than the first 10 seconds the loud thump is what I am experiencing.

https://www.youtube.com/watch?v=P7EFAGTCkko#t=71

It sounds and feels like you hit a big pot hole...BIG pot hole! 4 wheel drive stays engaged but sound happens very often but random. 2 Wheel drive drives fine.

I understand from what I've discovered is that this is a hub issue and I believe from a poor vacuum line? Is that correct?

This is where the other posts lack clarity...what is the best fix?
Of course I would prefer to keep the hubs locking via the button with in the cab but is the best solution to replace the hubs with manual locking hubs? Or is fixing the vacuum line a possibility?

Thanks in advance for any insight you might offer.

Any takers on this post?

Bad hub, broken spider gear in the diff, or maybe something in the transfer case is slipping (I've heard of occasional chain stretch issues in the past affecting the '98+ cases).

I would start with easy stuff (the hubs). If that doesn't pan out, jack the frontend up and spin one front tire watching/feeling if the other spins smoothly in the opposite direction (do this with 4WD engaged of course). Still failing to find the issue, I'd turn attention toward the t-case.