2000 ranger t-case noise

[frank b]

My dad noticed a humm from under his 2000 ranger so he did the simple things first like check the fluid in the diffs and t-case. He found that the t-case was a quart low... He topped it off and it still made the humming noise. He then checked the u-joints on the rear shaft, the front joint was tight so he replaced it. With the driveshaft off, and the truck in 4wd of course, there was no noise while driving the truck. It didn't need to be driven far or fast to hear the noise so just going back and forth in the driveway was all he did. The new u-joint didn't change anything once the driveshaft was installed.

What could have been damaged inside the t-case with it being that low on oil? Everything? I think it needs to come off and taken apart but I'd like to hear what you all think.
Anyone know of a good step by step tutorial online of a rebuild on the BW1354?

 

[mitch4x4]

For something like a transfer case where it only holds a fairly small amount of fluid a quart is a lot of fluid to be missing. I would be checking to see where that fluid went. And as for a hum I would think bearings.

 

[frank b]

There are no obvious leaks, it must be a very small one and it took a long time to leak out. We're going to keep looking. It shifts fine, it hasn't gotten louder, so he wants to just run it and see what happens.

I thought of rebuilding it, but the kit is just bearings and seals and a bushing. Bearings aren't the only thing in there that gets lubricated, and if they're worn, what else is??
I've been searching for a replacement, but it has the XL54-AA, and that was only on the 2000 model year, so there aren't as many out there.

Does anyone know of a list that shows what the different id numbers represent? I'd like to know if I could use a different one.

I found this site that shows what transfer cases were availble each year,

http://www.usedtransfercases.com/search/Ford~RANGER/