Land rover squecking and grinding from underneath when driving

I think you need a new gear-box sorry

A grinding noise suggests a bearing at fault or perhaps worn pads on the brake rotor.

However, the clunking noise you mention could also point to a problem with the drive shaft or differential.

The first thing you should do is to get under the vehicle and try twisting the propshaft back and forth. If there's any movement this points towards a worn universal joint on the propshaft. A worn universal joint can cause a clunking noise - particularly when pulling away. The vibration caused by a worn universal joint can also damage bearings in the differential and also to the splined ends of the axle shaft.

You're also going to have to remove the wheel from where the noise comes from and examine the end of the axle shaft/bearing.

The link below is of images of the rear axle:

land rover discovery rear axle Google Search

Sounds like your Gear Box is coming apart on the Inside or not fully engaging...

bad brakes or bad front axle joint (cv joint)

sounds like a worn timing chain--getit fixed before u buy a new engine!

The discovery is full time 4wd, you can change between high and low ratio, it sounds like a broken transfer case.

This noise is coming from the side back. like a grinding noise when you are driving. It lound to hear when you are seated behind the front passanger chair.

I'm not sure myself but do this test, find a baron stretch of road and drive up to 40 mph, then apply the brakes very firmly to try and lock the front brakes, you will notice 1 of 2 things, if the tires lockup and screech then no ABS, if you get a grinding pulsing action that doesn't sound good, then yes you have ABS, this action allows the wheels to continue to rotate to a certain degree. Good luck

sounds like your hand brake could be over or out of adjustment?
i bet the problem is related to a hand brake components