Xoutpost.com - Dead transmission? Transfer case?

Got stranded today. X5 2002 M54 auto

Was driving as I normally do, pretty easy on my vehicle.
Drove about 70km, then came to a red light and started just coasting, was probably going around 10kmph.
Then suddenly the car started making screeching noise, it was hurting my soul!
I changed to neutral and the noise disappeared. The same in park.
However if I shift in drive or reverse, it starts making that loud screeching rattling noise again.

I'm wondering if there's a way to confirm what died exactly.
Tranny wasn't acting up at all previously, other than taking a while to switch speed when I was accelerating fast (though the engine is dying as well I think, at full throttle the vehicle didn't really know what to do and would barely accelerate).

About a year ago I fully rebuilt my transfer case NV125, and drove at least 10-15k km. I really doubt my transfer case died.

At that point I did weld a new spline to the front driveshaft, so that it would insert more fully into the transfer case.

I'm thinking the only thing other than transmission would be my failed weld.

I've never dealt with a dead transmission before, and am wondering what's the best way to tell.

No engine light codes. When I put the car in drive or reverse, it does not move at all and does not even try.

I've owned the car for about 5 years, and changed transmission fluid and filter a few times, at least 3.

I'll get under the car tomorrow and see if my weld is broken.