4x4 knock: transfer case? cvs? diff?

Hey,
I have 94 navara with a TD27t in it. When i put it in 4x4 on the beach I am getting this knocking sound coming from the front end. It only happens in 4x4 so im assuming its either transfer case, diff, cv's or hubs. The 4x4 is working fine except for this sound. Would someone be able to help narrrow this down. Here are some things i've noticed
-Doesn't do it unless underload (i.e. didnt do it when i put it in 4x4 and drove down the bitumen road. but always does it in the sand)
-Sounds like something is correcting itself
-The volume of the noise is load related. If I go over a steep dune it knocks the loudest.
-i have jacked it up and tryed to find an obvious problem, got nothing, all seems good.
-I checked the oil in the transfer case and it was fine, also there wasn't any metal fillings on the bolt.
-cv's have a bit of play in them. I have never heard a stuffed cv but to me the sound im getting doesn't sound like what i think a worn cv would make.
-i have taken the hubs off but there is no wear.
-im leaning towards the diff, but really have no idea

Appreciate any advice.

Also, what diff does a 94 navara diesel have in the front. I'm just interested in prices.

For starters, don't drive on a bitumen road in 4x4. The system relies on a bit of slip in either the front or rear wheels or you can put great strain on the drivetrain. (Note, this is different to a full time 4WD system that has a centre diff rather than a transfer case.)

Another question, have you tried putting the ute in 4x4 but with the hubs unlocked? In reverse? Might help narrow it down a bit. I also suspect that if it were the CVs, you would have the same issue in 2WD and 4WD.

Can't remember what diff it has, either a 180 or 200mm diameter, I think. Look through the D21 forum, the info will be there.

Hi mate sorry to hear about ur issue. I stretched a transfer chain and sounded like ur symptoms. Only under load. Go on YouTube and search navara transfer case noise it will come up and than you should be able to work out if its transfer or not. Although I thought d21 had a stronger chain. Good luck and hopefully it's not to major

that sounds to me as problem with auto-lock wheel hubs - I almost 100% certain is one of them

Thanks for the quick replys. Unfortunately for me that transfer case noice sounded pretty familiar. Although i'm still not fully convinced. Any pointers to 100% pin point the transfer case? How do you stretch the chain? If it is the transfer case there should be no worries just using it till it shits itself, right?
btw. I have manual hubs

if you have manual hubs so it rather won't be them

mostly you would hear cv when wheels are at some angle, it's unlikely for them to be noisy when you goes straight

if its transfer chain you'd better fix it before it brakes and destroy everything around

One way to stretch the transfer case chain is by driving in 4x4 on bitumen roads.