I was told I need to replace the seal on the rear

A Chevy rear end or differential is filled through a plug. There is no provision for draining it, however, other than removing the rear cover. If it requires differential oil and the rear cover had not been removed for service, there is obviously a leak in a seal. At the same time, the fluid does not get contaminated and should not need to be changed under normal circumstances.
Read more: http://www.ehow.com/how_7578928_fill-chevy-rear-end.html#ixzz2xJG3hoNg

You must have a 4 Wheel-drive. You should have a driveshaft for that end of the vehicle and you should not let the Mechanic keep it. The rear unit must have a bad Pinion bearing or more damaged parts. Some of parts can "freewheel" without having power going through them.

But the metal shavings from broken parts can travel inside the differential and cause more problems. You don't always need the 4-wheel drive function and you do not have it since the Mechanic disconnected it.

Sometimes it can be what is called an "axle" bearing. Each side has this part so you have 2. The noise levels for this part can also change when the 4 wheel drive is engaged.

Make sure the rear differential has lube. Read the Web for articles about your vehicle. Search "2003 Ford Escape rear differential".

There is a Salvage yard site called Car-parts.com which is good for locating used parts like differentials. One would need to match the same gear ratio as the front.

You have to remove the oil pan first - the diff stays up in the body until you remove the pan, then the diff comes out.

THE LEAK is an axle seal leaking the noise is bearings in rear end could be axle bearing of carrier/pinion bearings while driving shift weight of truck side to side see if noise changes if so it is axle bearing if not then most likely differential bearings

does it get louder above 45-60mph? and much quieter at low speeds. It could be wheel bearings, a rear differential or front differential. If its a grinding humming noise its wheel bearings, listenin to see if theyre coming from the front or rear, left or right, or both when your driving to know what wheel bearing are bad. If its a whinning noise, its probably a differential. check and listen to hear if its coming from the front or rear. Also, check for loose plastic around the wheels. Lastly check your tires for uneven or choppy wear. move your hands front to back on the top of the tire. does it feel really choppy and rough, maybe you just need new tires

In my area it can be done for about 800.00 plus the cost of the rear.And in my opinion if the rear is rebuilt with a new ring and pinion gear that's the biggest part of the rear then I consider that along with new axle seals and differential gasket it would be almost new.This would save a large sum of money for one that's rebuilt.

Hi,
Sorry to hear of the problem you have.
If all the fluid did indeed leak out, and the Lincoln has full time all wheel drive, and the vehicle was driven with the front differential dry , the sad news is the bearings will have been scored (ground up).
Depending upon how long the unit was run dry, will depend on the extent of the damage.
One could try and replace the leaking seal, flush the differential, refill with new fluid, and see how it runs. If the unit was not run to long dry, the above idea may work.
A trusted service Tech should be able to help with the decision.
A differential can be rebuilt.
Regards,
Wayne

front or rear wheel drive ,as only ones i havew worked on are rear wheel drive ,so do you mean the half shaft seal

The term 'Rear End' when used with a vehicle, is a slang term for Rear Differential. Your engine turns the transmission, which in turn turns a driveshaft, finally turning the rear differential. The gears inside the differential turn axles, and your rear wheels are connected to these axles.

These two link explain the basics of a differential,
http://www.drivingfast.net/technology/Differentials.htm

http://auto.howstuffworks.com/differential.htm

The rear differential, has Nothing to do with why your transmission won't shift. Manual or Automatic. I suggest you find a competent shop, and leave That One Alone!

Not if you have them install a used on from a salvage yard it shouldn't.