X1 ................ use a 100mm x 1/2" wobble extension and ratchet or breaker bar directly in the plug, it works perfectly for me every time.

https://www.google.fr/search?q=100mm...vZhZhIqJsSefM:

 

For the transmission, you can install a pan from an auto D1 with the dipstick and tube, and use that to fill. I'm doing this on mine when I change the fluid again. As for the transfer case, I've noticed that sometimes it's a little different for every Discovery. My 04 D2 was nearly impossible to get a breaker bar on the fill plug. Took me at least an hour of fiddling with different 1/2" tools to get something to work. UJs and wobble sockets did not work in my situation. They just wouldn't stay in as I tried undoing the plug, but I can see that it could work if the plug was not overtightened like mine was. My 99 D1 (same transfer case) was actually very easy to get a breaker bar on. E-brake cable was easy to move out of the way. I had the bar go between the cable and the transfer case. On my new 01 D2, it seems to be like the D1 I had, it wasn't too bad. But this is just my experience.

What ended up working for me is a small Craftsman breaker bar. It has a flat head so it fits behind the parking brake drum. If you can get something on the plug and it won't budge, use a big hammer on the breaker bar. Believe me, I know your pain. You can get something to work.

 

I'll admit it's been 6 years and 47,000 miles since I changed the T-case lube but I don't recall too much trouble using a 1/2 inch torque wrench I bought in January 1984 at a store that was that era's Harbor Freight. It's the only 1/2 inch-drive tool I've ever owned. No wobble extension or anything else. Yeah, the brake cable was in the way but it wasn't too difficult to push it out of the way enough to get the torque wrench into place.

Can you get anything on the drain plug? Is the problem that someone before you just tightened it too much?

I suppose the inspection cover could be removed and a new hole drilled and tapped in it at the same horizontal level as the factory fill plug. That would be a mod that would (should?) make it easier to fill the T-case in the future. But perhaps the cross member would be in the way. I don't know; I don't have my truck here to check.

 

I'm with you, I don't see how a wobble extension can't get this done. I've use that many times with no issues.
The brake cable only has to move down slightly. Spray the drain plug with some PB Blaster first, and then have at it.

Maybe the OP can post a pic of what he is looking at.

 

Thanks for the correction. I meant the cable harness, not wire harness. I was typing too fast

 

This is what I use connected to about a 3" extension, then a rat$hit. The 1/2" wobble kind of wants to bind up against the brake drum if you don't have the tool in the correct orientation.

 

take the extension off, put the actual ratchet up inside there (you will find space that way) with nothing on it, its a magic trick. i had the same thing. the ratchet sits up and to the left and i just ratcheted an inch at a time reaching up, the ratchet was never hanging down. there is wiggle room.

 

Exactly 04Rover! I mentioned the same thing in post #2... I will use one of a previous poster's pics to illustrate it..... just position the ratchet (without using any extensions) through the area as circled in the pic..... and fit the ratchet socket directly into the drain plug.