https://landroverforums.com/m_52625/tm.htm
Just read the first post of this tread, I bet this is what happened to you.
And to answer your question, the double-cardon joint is two u-joints in one unit. It is where your front driveshaft connects to your t-case. When they go bad it slaps your transmission and puts a hole in the side.
Your t-case should be fine, but who knows. I would look at it myself if I were you.
I dont know how many miles are on your trk but I doubt the trans just gave out, ZF makes a very roubust transmission. Theyalso make off-road trans for dump trucks and bulldozers, BMW and Jaguar.

 

I have 130,000 miles on it, but like i said I was just driving and it just stopped working, I took a look under it and it looked normal no gushing puddles or even dripping. i was just driving and it went "neutral" then it caught and didn't sound healthy. I got to a parking lot, shut her down then when I fired her back up is when the S/M and D lights started bkinking at me. But everything LOOKED normal

 

Huh, strange, maybe it sprung a leak and ran out of fluid. Oh well, your getting it fixed for pretty cheap it sounds like.

 

Ya I am, Just trying to find a good cheap tranny and transfer case. Then hope that I don't blow anything else, it would be nice to just have the thing run good for longer than a month. I love my truck just wish I could drive it for awhile

 

I heard somewhere before that if you are going to own a LR you also need a Toyota or Honda so that you have at least one reliable car.

 

Ha Ha!! that seems to be the case, Luckily I just use my girlfriends car and I do have a company vehicle so Iat least I have a way around so I can go visit my land rover during visiting hours at the shop