Pajero gear box

If you mean putting it in low range...not really.

2WD to 4WDH (4WD high Ratio)
Just move the lever. This can be done at speeds up to 100km/hr.

4WDH to 4WDHlc (4WD locked center diff)
Again just move the lever. Not sure of the speeds..It's on the label on the Drivers door.

4WDHlc to 4WDLlc:
Stop!.. Move the lever to the neutral position. Then move it to 4WDLlc. Drive off.

Sometimes you need to reverse several meters to unlock the diffs, but you shouldn't need to do this to lock them...I certainly never have and I've had an NH and an NM.

Peter

Mine did that on the sand too. Solution run low range in the dunes.

Mickey

What tyre pressures were you running?

If you didn't drop them to an appropriate level (~20psi perhaps) then that could be the cause. Did your engine temp rise at all?

In auto's you are better off running in low range to keep the engine revs up and keep the torque converter slip to a minimum. It is the torque converter slip that heats the fluid and leads to overheating.
A lot of auto 4wd's have very marginal cooling capacity in sand because the heat from the transmission fluid heats the radiator coolant up to the point where the engine overheats and then kaboom!
Earlier diesel surf's, jeeps (the engine management system shuts the engine down when they get too hot), pajero's and a few of the soft roaders and mid range 4wd's are especially susceptable to this problem. Most of the larger vehicles, cruisers and Patrols seem to be able to cope but any with partially blocked cooling systems will have trouble.
Check your ATF fluid for burning and if it smells burnt or has a brownish colour change it completely, usually easier and cheaper to have a trans shop do it too.
If you want to do a lot of sand driving you may be advised to put synthetic ATF in as it handles heat better.

Thanks to all that responded. This is the first time I have used a forum and think it's just great. I have had experience driving in sand, that's why this was a mystery as I thought I was doing everything right, although I had never driven on the beach with an auto. My tyres were deflated to about 15. I was in high range, which seems to be the issue with autos.
Thanks again for all the feedback.

Chops

Strange one that. Never had the problem and have driven many times on Frazer Is, as far as waddy point and North of Noosa to Double Island Point.

I never drop my tyres below 20 PSI. 16PSI is considered as low as you should go. I like to have some tyre pressures to play with if I get in trouble.

Sand driving relies on momentum. Hence High Range is ideal. Enjoy the experience and the Paj.

Sapper