Is this guy talking arse?

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tombardier

tombardier

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[ame="http://www.youtube.com/watch?v=R7QAARZBOlU&feature=related"]YouTube - 4x4 Driving Techniques - True 4WD[/ame]

This guy, a couple of minutes in to the video starts going on about how you're not in true 4 wheel drive unless the centre differential is locked, and you should just leave it locked at all times in an off-road situation? Am I right in thinking that this is bollocks? My 90 has a diff-lock, and I believe that this is a centre-diff-lock and I certainly wouldn't use it unless my wheels were going to start slipping on one side and the wheels on the other side would stop getting any power..

Correct me if I'm wrong.
 
erm you wont have true 4 wheel drive unless you have both axles locked too



edit: got halfway through the vid and lost the will to live, so i turned it off and watched this instead
[ame="http://www.youtube.com/watch?v=q2I17OtZp6E"]YouTube - Series Land Rover Driving Instruction Part 1[/ame]


[ame="http://www.youtube.com/watch?v=PwlALeoBOKU&feature=related"]YouTube - Series Land Rover Driving Instruction Part 2[/ame]
 
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Ok, this helps (stolen from elsewhere!)

You have 3 differentials on your vehicle
1 in the front axle
1 in the rear axle
1 in the transfer box which is controlled via the low to high range lever, move to the left to lock for off-road, move to the right to unlock for tarmac
RR, Disco and Defender are all full time permanent 4 wheel drive. However, to enable these vehicles to go round corners on tarmac they need a centre diff to stop the transmission from winding-up. The inside front wheel on a left hand turn will rotate the slowest and the offside rear wheel will rotate the fastest and there will be a difference in rotational speed from front to rear which is why LR fit a centre diff to compensate for this difference. Vehicles such as Suzuki's 410 have a second lever that has 2 wheel drive high, 4 wheel drive high and 4 wheel drive low and there is not a centre differential. With these vehicles you use 2 wheel drive high on the tarmac and only the rear wheels are driving. When you off-road any vehicle the loose surface allows the transmission to compensate for the change in speed front to rear.
So when you were trying to drive on grass (loose surface) the front nearside lost traction first, the centre diff put all the torque to the front axle, the front axle diff put all the torque to the nearside wheel, end of play!
When you engaged the centre diff lock the front and rear axles both received the same amount of torque and the rear wheels and front wheels both gave you grip. In all probability the front nearside was spinning but the rears with lots of load on them had enough grip with the ground to give you forward motion.
Then the competition off-roaders on this forum who get into some tight situations have another weapon up their sleeves, they have diff locks in either their front or rear diffs or both! With the centre diff locked and the front left and rear right wheels off the ground (what is termed cross axled) you will not get any drive since the front and rear axle diffs will put all of the torque to the 2 spinning wheels. With axle diff locks the torque is split to both wheels and then you only need 1 wheel to grip with 3 diff locks engaged to drive the vehicle.
Click to expand...
 
If you did as he says and went into diff in all offroad situations you would end up with damaged halfshafts and flanges and extra stain on the whole drive train, to sum it up in one basic phrase: "when traction is likely to be lost" you could be offroad on rocks that offer good traction - I would certainly not even think about difflock in that sort of situation.

However he is out in Africa, lots of gravel tracks etc, so if he puts it into diff then corners sharply the back wheels which want to do less revs that the fronts (because they cut the corner) can "scrub" on the gravel, try this on tarmac and you get windup and all the strain. So if I lived in africa and I was driving along dirt tracks all day with lots of traction I probably would NOT use diff, but if you want to drive fast on these gravel tracks and I would consider it as it does increase tractions (think of subarus rallying - they do a good job due to their AWD).

Next time you are in a garvel carpark with some spare space, engage diff, and go full lock and drive, open the window and listen for the back tyres they will make a sort of skidding noise on the gravel.
 
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I will investigate this at the weekend, but I think the land rover will behave like the slitty did when it was in "4 wheel drive". Before he engaged those hubs, he has NOTHING to the front. Althought not locked the land rover will always be in 4x4.
 
Use difflock when traction is likley to be lost.

This does not JUST mean when the wheels could spin this also means when you are likley to lift wheels like rock crawling when grip is extremly good.

Always lock difflock the strain will be more and transmission wind up is more likley if you have very good traction like on tarmac with grippy tyres and drive for some time, tens if not hundreds of miles then you may cause serious transmission damage but again I doubt it. It most certainly will increase wear of tyres and all drivetrain components. Usually when venturing off road or off tarmac knock it into difflock and select an appropriate gear to get you, to the start, through, and out the otherside of the particular area you want to cross. You can easily damage your transmission if you do not put it in when you need to due to the weight transfer from front to back will send the center diff billio. Also putting difflock in after you are stuck is too late momentum has been lost and you will most likley still be stuck.

Don't be afraid of using it.

Jai.

I have seen a new defender 90 written off because somone told the man not to engage difflock of fear oif transmission wind up. He drove down a hill decent lifting a wheel ever so slightly with no engine braking he shot down the hill and rolled the mota.
 
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I have driven at speed up was covered in patchy ito 55Mph using difflock for 30 odd miles when it snowed in Feb. The road ce/snowand and difflock worked extremly well indeed. I have also driven a Toyota hylux up to and over a mountain pass plus another 3.5 hours in perm 4wd with no ill effects other than solid feel and a most secure feeling when driving to Kabul From Gardez in winter when going slow and steady was not an option. Jai
 
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Totally agree with Jai.

A diff that has one side spinning and the other stationary is more likely to fail. The centre diff in the gearbox is a lot smaller than the ones in the axle.

If it is not tarmac or a gravel track then I lock the centre diff.
 
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