silly question perhaps, but..

Rich,

Not a silly question but a hard one to put into words.

This is what happens when the vehicle is in 4WD mode, hi or low range it does not matter, and in the case of costant 4WD, with the centre diff locked.

Transmisson wind up(TWU) will not accure if the vehicle is driven on a hard flat surface in a straight line.
TWU will accure if the vehicle is turning on a hard flat surface.
TWU is created by the front wheels travelling at a different distance to the rear wheels, eg, doing a "U" turn.
TWU will not happen if the front or rear wheels can slip.
Slip can occur when the wheels are on a lose surface like mud,dirt, or sand.
Slip can also occur when one or more wheels leave the ground.

So to answer your question,
your vehicle can be safley driven over a rocky track in low range 4WD locked centre diff with out any damage to the transmission.

When I do the 7 day Vic High Country I am in 4wd mode for the 7 days either hi or low range and only take it out when I hit the black top, and on that trip there is a great variety of track condictions

Having some form of locking front or rear diff would mean that the wind up would accure in the axels as well as the transmission. Air lockers should only be used when the going gets tough and turned off as soon as possible.

Wayne

Yep wondered the same thing the other day when I climbed a steep granite rock that needed L1 but there wouls have been no slip I guess too much of it would be detrimental but if there is a bit of loose gravel on part of the track that would help but otherwise could be a bit of a tricky one

Just an aside.......
Most of the older type vehicles get gearbox windup when driven in Low Range for a period of time. When you stop and try and disengage the gearstick, it wont let go. With my GQ I reverse about 5 metres and then the lever slips back easily. THis has happened with most of the 4bies I have owned.

Hi Rich.
Wayne answered your question well.
is not something that can be explained well, but the application of the various units of your truck, where and whe nto engage what only comeswith time and experience.
Perhaps I could suggest that if the track is just rocky but not too rough try leaving the centre diff unlocked, as long as you do not lift a wheel it will drive as well, plus you will learn to use the inertia to pass over small points that will get you cross axled.
The further you learn to drive with out all the extras will help you in the future, when you have them you will have a bettewr idea of when to use what.
I use all 3 diff locks most of the time as I find it is kinder to the truck, but there are cetain track conditions that diff locks a particularly the front is a hinderance to the truck and driving.
i do differ from a lot of people in that I lock all diffs on steep down hills, as this aids truck control and prevents one wheel from loosing traction
This is a big field to cover and a lot differs onteraine and vehicle type
Ray

Thanks for all the interesting replies! Re the response to leave centre diff unlocked, no can do in a Prado once in Lo range. I'm referring to a steep, very windy, very rocky, long uphill climb that didn't have much loose dirt/rock. The further up I went, the more I was expecting a big noise from the centre diff. Hard to stop halfway up and go into hi range to unlock the centre diff momentarily, reversing not an exciting option either, but I guess if this was a major issue, no one would be getting into the rough rocky stuff, diff-locks would be failing left, right, and centre (sorry, front, back and centre).

Thanks again - any further comments welcome!
Rich

Gotcha Browny, I can see how that would sort out the windup occurring as a result of inside/outside wheels travelling further, but woudn't there still be an issue at the centre diff? The rear wheels won't travel as far as the front, on a windy climb.
Hope that the unweighting of certain wheels is enough to allow the slippage.

Cheers for the reply
Rich

Richie,

Good question you asked and I hope you got the info you needed.

If you are concerned about TWU a trick I was taught when doing my Off Road Cse with the Army was once you get back onto bitumen put the drivers side wheels on the bitumen and keep the passengers side wheels on dirt and drive in reverse for about 10 - 20m. This should help - it is similar to what Willem said.

Enjoy your driving.

Karl