I better ask this before I break something...

[gords]

OK, I've just got hold of a Drivers Manual (thanks Matt_H) and read the gearbox and transmission section.

More specifically, the Differential Lock bit.

Firstly, I claim immunity from smart-arse replies because this is my first 4x4 and I've only had it a short while :lol:

OK, the questions - is my Discovery permanent 4 wheel drive? If so, what is the diff lock doing and why does the manual say "ALWAYS unlock the differential for normal road driving"?

OK, start shooting

[datalas]

The discovery is a Perminant 4 wheel drive.  That is power is applied to both the front and rear wheels.

During normal driving conditions there are occasions where the front wheels (as a pair) need to turn faster than the back ones (as a pair) and vice versa.  In the same way that the left wheel may need to turn faster than the right one.

To cope with this a differential is used, which allows power to be distributed more evenly, or at least allows one side to spin at different rates to the other.  

A discovery has three diffs, one in each axle, front and rear.. and one in the middle.

There are of course occasions off road when you do not want to distribute power in this way, for example if you lift both front wheels off the floor, since they are easier to turn they will get 100% of the power delivered by the engine.   This will leave you floundering like a beached whale.

The Differential lock "locks" the diff, that is to say, it essentially turns it off, so 50% of the power goes backwards, 50% goes forwards.  This will allow you to get out of some nasty situations, but would result in unpleasent handling if used on road (which has good grip etc)

Ergo (as it used to say on the little red plate) "the differential lock should be engaged only when traction is likely to be lost"

Hope that answers the question

[Colin 009]

Ok I be gentle  :lol:

Yes your Discovery is permanent 4 wheel drive,

As I understand it the diff -lock, locks the front and rear diffs together.

Well done Datalas beat me to it.

[gords]

OK, got it 8)

I was under the misconception that it was normally 2 wheel drive and the "little gearstick" put it into 4 wheel drive, high or low ratio.

So, what's all this about my transmission getting "wound up" and what calms it down again

[Andy.]

Excellent summary there Daz  :D

So you did go to school, or have spent all your years around Land Rovers  :lol:

[muddyweb]

The 2wd / 4wd is true of vehicles like the Series Land Rover... they (for the most part) don't have full time 4wd


Wind-up is what happens when your diff lock is engaged and the wheels are trying to turn at different speeds (going round corners for example)

You get a build-up of energy in the drivetrain which will be released when a wheel loses traction sufficiently to slip.

It often manifests itself when you try to disengage the diff lock, but the light won't go out.  It stays 'stuck' in a locked condition.

Reversing for a few meters whilst turning from side to side will usually cure this.

[gords]

You get a build-up of energy in the drivetrain which will be released when a wheel loses traction sufficiently to slip.

Is that the only "release" or does it have the potential to actually break something?

[muddyweb]

In *very* extreme cases, damage can be caused.  This is only likley to happen if you keep the 4wd locked whilst driving around on tarmac though..   On the slippery stuff (even on grass) there is normally sufficient opportunity for the wind up to release periodically.

The LR drivetrain is reasonably tough if you look after it.

[gords]

Thanks for the very helpful replies. It does mean that I've got no excuse now though

[gords]

OK, so I've done a couple of laning trips which were muddy and slippery so I mainly used low/diff lock.

I went to Whaddon where it was very muddy and very slippery so again I was in low/diff lock.

Bramcote was a similar story.

Now then, I'm doing the Wales laning trip this weekend and I understand the terrain is varied. Therefore, my question is - what situations/terrains fully require diff lock and which do not (i.e. do not!)?

I'm sure this is a "situation specific" thing, but any guidance and/or general rules would be welcome :)

[muddyweb]

The very general rule is that if you think the vehicle may lose traction... have the diff lock in before it does :-)

It's a case of reading the terrain really.  There is no problem engaging and disengaging the diff lock when you are moving.

On a lane, I tend to leave it out unless something looks slippy ahead, then knock the lock in until I think it all looks OK again, then take it out.

[gords]

It's a case of reading the terrain really.  There is no problem engaging and disengaging the diff lock when you are moving.

Umm, I read in the Discovery manual that you could engage/disengage while moving, but it sounded quite complicated - less than x speed, wheels straight, blah blah :?  I did think that I should read it more thoroughly and practice some time - not got round to it though :(

On a lane, I tend to leave it out unless something looks slippy ahead, then knock the lock in until I think it all looks OK again, then take it out.

I think my head still thinks that you need to "do something" to prepare the car before you go off the tarmac :)  It's probably down to lack of experience :)

[Wanderer]

Next time you're out I'm sure someone will take you through the changing in and out of d/l and hi/low box. It's just practice.

Ed

[muddyweb]

Don't get the diff lock confused with the high / low selection.

Diff lock (i.e. shoving the lever over to the left) can be engaged at a fair speed.   The main things to be careful of are that you are pointing straight ahead and that you don't have any wheels spinning at the time.  If either of the above aren't the case, then you need to stop and put the lock.

High / Low selection can also be carried out on the move, but it's a bit more of a black art, and to be honest with you, the benefits of doing it when moving are pretty much non-existant in the vast majority of cases.  99% of the time, I stop to change from high to low or vice-versa.

[Wanderer]

Changing low to high is the easy bit.  :lol:

Ed

[gords]

Don't get the diff lock confused with the high / low selection.

I can see that it would not be good to get these the wrong way round :lol:

Diff lock (i.e. shoving the lever over to the left) can be engaged at a fair speed.   The main things to be careful of are that you are pointing straight ahead and that you don't have any wheels spinning at the time.  If either of the above aren't the case, then you need to stop and put the lock.

Do you need to use the clutch, just take your foot off the gas, or just ram it across  :)

[LOFTY]

Another good note, if diff lock is engaged, and you get a puncture, dont start undoing the wheel nuts, while your mate jacks it up, i have seen a freind smacked in the face, when the wheel was lifted, and the wheel rotated from the tension in the drive line. :oops:

[muddyweb]

Do you need to use the clutch, just take your foot off the gas, or just ram it across  :)

 :lol:    um... yes, you can just ease it across :-)

[Bob696]

just to spread the targets out a bit  :lol:  here is my question

when do you use low and when do you use high? :oops:

[muddyweb]

ahh, now.. that is very much more a 'piece of string' question.

Gear selection is dependant on the terrain, traction, engine power, and a few more random factors.

It also depends entirely on the type of driver you are, and how quickly you like to tackle any given obstacle.


Basically... I have no intention of giving you a definitive answer to that ;-)

[Hightower]

Diff lock (i.e. shoving the lever over to the left)

'shoving the lever' indeed.  Those of us with more refined motors just have to press a button  

[Paul]

Diff lock (i.e. shoving the lever over to the left)

'shoving the lever' indeed.  Those of us with more refined motors just have to press a button  

Indeed we do  :D

[Thrasher]

Make sure it is not abused by SWMBO eh? At least in an auto the gearstick is ignored by said fairer sex ;-)

[Topple]

Hi Gordon

You MAY need difflock saturday  :lol:

only on one rock climb, saying that though, its not necessary, just makes it a bit easier.

My series 3 gets up it no problem without any gadgets  :lol:

Anything your not sure of just ask, will be happy to help.

See you Saturday

Paul

[muky-kid.]

:D  Basically its all down to personal preferance and practice, when first started offroad driveing it took me about 3 months weekend driveing on differant terains before i was confident enough to know when were and what gears to be in wether in low box ,high box and when to use the difflock etc. Anyway its more fun sometimes when we get it wrong and have to get a tow out from your mates. And first to admit its happened to me quite a phew times..... :lol:  Just take it easy dont rush or panick and soon youll be doing it with your eyes shut ( gear changes not driveing ).

[Range Rover Blues]

Most of the 4x4 magazines would have us use low-box all the time, I did this when I first started laning (quite recently compared to some) and quickly ran out of gears!  Fortunately we have a Borg Warner transfer box so diff-lock is just not an issue.
I would think that most if not all difflocks can be engaged/dissengaged at any time when the car is stationary or travelling in a straight line BEFORE one of the wheels starts to slip, you are after all engaging a gear that locks the front and rear axles together!
Most of the time that I'm changing low to high or vice-versa is when I'm towing (or sat in traffic) and I use low box to protect my clutch.  Observe how your biting point seems to change when using low/1st to pull away!