Land Rover Repair: all wheel drive not working, high gears, rear axles

Question
I realize what you are saying, but, several months ago I threw a front u-joint, thought I might be able to drive without it, but I could'nt get the rear wheels to move at all, maybe I'm just not working the diff shift lever properly, and to add to the question, on the shifter, I know the right side is for your low and high gears only, but when you go to the left to lock in the diff, do you stay on the left side up for low, and down for high, last night I tried it and it seemed to work, all four wheels seemed to work when it was engaged and in the left up and down positions, and one other thing what does the constant beep or ring mean, does that mean your engaged or in nuetral.Thank you for replying.
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The text above is a follow-up to ...

-----Question-----
My 96 disco 1 is only working in front wheel drive, I tried to engage the diff lock yesterday and noticed it's only using the front wheels, it feels like it's engaging, but no movement out of the rear wheels, no noises comeing from the transfer case or anything that sounds wrong please help.
-----Answer-----
I think you are misunderstanding what is happening in your truck.  You have an all wheel drive system with a center differential that allows the front and rear axles to turn at slightly different speeds when cornering.  The diff lock lever locks that center diff to prevent the truck getting stuck.  Your truck is always driving all four wheels

There is no front wheel drive mode for your Discovery.

Does that answer your question?  If not, please clarify what your problem is and I'll try and help  

Answer
OK, your info makes things clearer . .

The beep means the transfer case is in neutral.

The reason you could not move until you locked the center diff by moving it to the right is that - with no connection to the front wheels - all the drive energy simply spins the disconnected drive shaft flange.

The centger diff is working just like a rear diff on a car, with one wheel on ice.  The wheel on ice spins, and the wheel on hard pavement just sits there.

Only by locking the diff can you drive, in both cases.