OK back to the Drawing board...
caught up with a fellow Zooker in Darwin and he suggests its nothing simple, note these simptoms...:
1. 4th gear pops out (mainly when accellerating)
2. gears not sloppy (or not sloppier then usual for Jimny)
3. gear actually feels tighter in 4th before popping out
4. doesn't crunch into gears
5. occured by staying in 4 gear for 12 hours on shakey arnhamland road
6. OIL LEAK FROM REAR SEAL (can't believe I missed this)
fellow zooker (thanks Joel) after looking at it suggests sinchro or (apparently more likely cos no crunching) something like the bush and spring that holds the gear in place, so...
is there ANYONE in darwin area that can help me fix this without me having to morgage the house I don't have... or
is there ANYONE in the country that has a vvt gearbox, refurbished or used

thanks for listening!
Miki