Use of standard diff lock explanation for ignorant newbie?

I have a standard 1987 Land Rover 90. I am about to put in a standard refurb Ashcroft transfer box. I don't quite understand what happens to the drive when 'Diff Lock' is engaged. I will only need it to get through the snow on the five-mile potholed single-track road from my pit to the nearest village. There are a few moderate inclines on this road where in normal drive one loses traction to the point where one can proceed no further. Please could any of the Landyzone experts explain to me in simplish terms what happens to the traction if I engage the diff lock? Does it lock the two rear half-shafts together if one wheel has a grip but the other is spinning or stationary? Does it do anything to the front axles when engaged? I'm being a bit thick about this and would appreciate an explanation of when to use it and what happens to all four wheels in snow, doing an incline...
Thank you!

The diff lock is only in the transfer box, The axles (as standard) are open diffs not lockable.

If the diff is locked it means that the connection between the 2 output shafts (bits that you bolt the props too) are now a solid connection and will turn at the same speed. Putting the same turning front and back.

If you are not in diff lock then you could come to a standstill with just 1 wheel spinning.
If you are in diff lock you would need to have 1 wheel on each axle spinning before you are stuck.

Dont use it on dry/slightly wet surfaces should only be used on slippery/loose surface otherwise you could end up with transmission wind up.

Basic enough for you?.

J

Thank you - nicely and clearly explained. I would only use it in the snow and where there might be some moderate underlying ice from the previous day's snow thawing and then freezing overnight. As I understand it, nothing works on 100% sheet ice anyway - you are simply sitting in a two-ton skateboard with no control whatsoever (I assume?). I'd never use it on a dry/slightly wet surface which presumably the normal drive would cope with anyway, There might be the odd occasion to get through some very loose gravel with a light trailer but I never tow anything more than 1 ton as the old boy is retired and excused heavy towing duties. And thank you for reminding me about the 'wind-up' problem. There's a method to unwind it, isn't there, should one find oneself having wound it up a bit in the first place?

Hector the Bad said:

There's a method to unwind it, isn't there, should one find oneself having wound it up a bit in the first place?

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Some say reverse a bit. Some say find a grassy verge and put 2 wheels on give it a bit to spin a wheel should release the wind up.

Personally only ever had it once (not in a LR) so its pretty rare to not beable to shift it out of diff lock IME anyway when used in the right place/time.

J

Simples! Thank you...

It is good to exercise the lock now and then as well as the high/low just to keep the mechanism free. Fine to do this on any loose gravel or grass area.

tottot said:

It is good to exercise the lock now and then as well as the high/low just to keep the mechanism free. Fine to do this on any loose gravel or grass area.

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Should also be fine on any surface in reverse with the steering centered? Only needs to be a few feet

kermit_rr said:

Should also be fine on any surface in reverse with the steering centered? Only needs to be a few feet

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Why reverse? Few feet forwards or backwards makes no diff oopsun)

Using all positions on the lever I can do and hardly move the 90 just to move the linkage.

J

That supposed to say ( opps pun) not oopsun)

J.

marjon said:

Why reverse? Few feet forwards or backwards makes no diff oopsun)

Using all positions on the lever I can do and hardly move the 90 just to move the linkage.

J

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Just testing that's a series thing to keep the wheels straight with no cv joints in the hubs

Thank you every one for explaining the basics - I'm not off-roading so this info will be good for making the difference between being snowed in and making it to the village shop for a pint of milk and ten B&H etc.

I have one more niggling question for anyone interested enough to explain the answer: where would a limited-slip differential come into this, presumably only on the rear axle? How would the individual wheels behave on poor adhesion surfaces such as loose gravel or snow/ice? Would a limited slip diff in, say, low drive, be a powerful weapon to keep the Landy moving (no load or trailer or pulling tourist's car out of ditch....

the biggest weapon, in my opinion, is winter tyres, followed by smooth driving, no sudden speed/direction changes
a limited slip diff helps prevent one wheel on the axle spinning without the other, I would say tyres are more important for the average road user

Interesting. Luckily, my tyres are fairly new General Grabber which are good on the rough bits for keeping going but have to be used with some caution under heavy braking on a normal or wet road. Great for grabbing but a bit of a roller skate for sudden stopping - but my previous TD5 with General Grabbers was much the same. So a limited slip is obviously a significant upgrade in keeping traction, given smooth driving and no aggressive speed/direction changes...

a limited slip diff (LSD) is used on sports cars to help maintain grip and help stop the back end stepping out under harsh acceleration, but allows the car to go round corners without issues caused back a locked/solid diff
a locking diff would be better than a LSD off road where speeds are much slower. some 4x4 have a LSD centre diff and you need to maintain power to encourage initial slip, so the diff locks, but as soon as you come off the power, the diff opens again. at least, thats how i understand it

marjon said:

Some say reverse a bit. Some say find a grassy verge and put 2 wheels on give it a bit to spin a wheel should release the wind up. J

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Jack a wheel clear of the ground

It's surprising how many people fall for the 4WD 'go anywhere' slogans.
The only way you will get genuine 4wd is with a pair of cross-axle locks, which are tricky blighters when you want to turn, even if the unit is only fitted to the rear axle.
I'm assuming today's electronic wizardry gets around such traction issues, but I only know about 'real' 4x4's.

norseman said:

Jack a wheel clear of the ground

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Was gonna put that on the list, but it involves effort.

J

ok - a limited slip diff would be a bridge too far for my limited use. But if I engage the standard diff lock, jack up say a rear wheel and then try to turn the wheel by hand, I assume the wheel wouldn't rotate with the diff lock engaged but would rotate if it wasn't engaged, provided the handbrake isn't applied and the gearbox is in neutral (with nicely wedged wheels on a flat surface (or is that too dangerous?). Or am I barking up the wrong tree, as usual?

Hector the Bad said:

ok - a limited slip diff would be a bridge too far for my limited use. But if I engage the standard diff lock, jack up say a rear wheel and then try to turn the wheel by hand, I assume the wheel wouldn't rotate with the diff lock engaged but would rotate if it wasn't engaged, provided the handbrake isn't applied and the gearbox is in neutral (with nicely wedged wheels on a flat surface (or is that too dangerous?). Or am I barking up the wrong tree, as usual?

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Refer to the 2 examples in my first post.

J

If a car with centre diff lock experiences wind up, even if you manage to disengage the lever, which is not obvious, the pressure of the wind up will keep the stuff in the transfer box locked, hence reversing, a few inches even, is enough to unwind it and free it off.
Ashcrofts and others recommend always engaging difflock in any off road or slippery surface use, cos a spinning wheel can rapidly destroy elements of the transmission.

I've got an LSD on the back, this has worked a few times, in snow and hauling up boats up slipways onto a gravel carpark.
Because of this I've only needed the diff lock a couple of times, driving across a field in over a foot of snow and up a slope in snow.
Even chunky tyres can get clogged with snow.