Your 93 classic should have the borg warner viscous diff, if there is no diff lock on the high-low knob then it's as it should be.
This means you can drive the car even if one axle has fallen apart.
If the front prop turns with the back then the box is ok, as things stand.
If turning the prop makes no difference to the front axle ie it doesn't turn then it's a CV joint, diff or halfshaft.
Now, a favourite for these is for the viscous diff to overheat and lock up completely, though I've never seen one. When this happens the CV joints normally fail, because it's when turning that the transmission winds up (the front needs to go faster than the back) and this is when the CVs are also working hard.
Listen for a light clicking in one of the hubs.
If this is the case you can swap the CV by removing the wheel, calliper, hub and then the stub axle (loads of oil) and pull the remains of the CV out or the half shaft as appropriate.
The tricky bit is knowing which side is duff.
Jack the car up, take off the wheels and force the brake pads back into the callipers so there is nothing stopping the wheels spinning. turn the prop by hand and see if one wheel moves and the other doesn't. Big clue. Try it straight ahead and with the wheels turned. If nothing happens you will have to make a best guess and start there.
If both half shafts are fine (CV and all) then it's time to pull the diff (you need the halfshafts out anyway).
Once that's fixed you need to sort out the cause straight away. If you can't make the viscous centre diff spin at all, even with a lever then do not drive the car until it's replaced.
New viscous units are about £300 give or take, look for a S/H one if that hurts tto much.
Yes I have one
P.S. asa guide I can just about spin the front prop when trying to undo the nuts to remove it, this is how stiff it should be.
