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[texaninmass]

Phototone is correct however to maybe provide a bit more information, when you activate the differential lock either in high or low, it locks the front and the rear differentials together connected through the transfer case...this means the front axle and the back axle get 50% each from the transfer case.

This does not mean that all four wheels are going to produce equal amount of power.

If you imagine one axle at a time...on the front axle if you get the right tire stuck in the mud the power is transferred from that tire to the left tire. This is done because on the road car tires need to have the ability to turn at different speeds.
The exact same theory applies to the rear axle. If your stuck in the mud on the right tire, the left one is transferred all the power.

If you follow that you can see that what most people think what is "true" 4 wheel drive is not.

Guys that use the trucks for off road use will usually install what is called a "Locker" on both the front differential and one one the rear.
This means that when they lock there transfer case differential lock it not only is distributing 50% equally to the front and rear axle (Differentials) but the "locker" also locks up both the front and rear axle respectively gaining the maximum amount of torque to all the wheels at the same time.

As far as the actual shifter, I had a hard time for quite some time understanding how thing actually works. I think the diagram in front of the shifter is confusing.

When the shifter is in the bottom right position, this is the normal driving for regular use.

If you push it to the left that locks the diff lock front to back in high.

If the shifter is in the bottom right position and you put the car transmission selector in nuetrul...you can the push the lever from the bottom right up one click and that puts the transfer case in neutral.(I am told you use this for towing purposes)

If you are in the bottom right position and you push the lever all the way forward (to-wards the front of the car) you are in the low position. This does not lock the differential however in low, it just puts the transfer case in low gear.

From that position if you push the lever over to the left (Toward the steering wheel it will then be in the "Low" locked gear.

Whenever you are in the locked range, both high diff lock and Low diff locked there should be a light on your dash indicating this. I have heard that some Rover take a bit for that to come on or off.

If you have not used this feature regularly then the lever and all that attached below to the actual Transfer case can become seized. There are many links on this site of how to repair that if that is the case.

I am sure there are others that provide more info as well.

Anthony