"HL"

Without getting techy the difference is that you can drive on high grip surfaces in H and for the real slippery stuff you can use HL.

H allows slip between front and rear while HL locks front and rear together like in a normal part-time 4x4.

Yeah, utemad's right. H means you can drive on the road or any hard surface, HL means it's like any normal 4wd where you back and front wheel become locked together giving you much more traction when off road, if you drive on the road in HL you will end up snapping somthing bad in your drive train as there is no give between the fron wheels and the back wheels when corning etc.

HL means that the centre diff (inside the transfer case) is locked so equal power goes front/rear. There is no "proportioning" between front and rear apart from this.

So, you need to use HL whenever you're in a situation where wheel slippage is possible. So you need it locked in all 4wding situations, such as loose gravel, hill climbs, sand etc. And of course, you must have it in H (unlocked) when on high grip surfaces such as bitumen.

What practical difference does HL make? Take a situation, where you lift or lose traction to one front wheel. If in H, all power will go to that front wheel and it will spin, and you won't go forward. However, if in HL, the power will still go to the rear wheels, so you'll make forward progress.

There are a couple of ways you can damage your driveline. One is to be in HL when on bitumen - get transmission wind-up because front wheels travel further than rear wheels, and all those forces will break something. Second way is to only be in H when 4wding, lose grip on a lifted wheel, then it will spin and come down with a crunch as all the power goes to it.

Cheers
Phil

thanks all, that gives me alot to work on.

cheers and beers

darb