found out the hard way tonight
would appear my transfercase may have shat its self, it has not been in 4wd for quite a while and have noticed a slight rattling clunking noise for a while, last time it was used the car got a massive work out, pulling 2 lots of dead weight up a steep slippery incline and these was some clunking and thumping going on.
so tonight went down the beach, bogged down in 2wd, popped it into 4H, sounded like a loud ratchet, went to 4L same thing, you can hear and feel it select and lock in, even got under the car, popped the selector off and manually selected, just in case, but no luck
dropped down to 10psi and managed to crawl out in 2wd onto the hard stuff and gunned it back off.
hope its a simple fix if not ill have to unbolt the spare one and put it on