Swapped the rear end and rebuilt the brakes.

This was the one with the frozen rear end. AWD. Dana 35 replacement from a junkyard.

Well.

It has 2 gears right now, and doesn't like shifting between them. My gut is telling me that it is crudded up passages, and hopefully stuck *****.

What do y'all think?

I only drove it 4 miles, and it went from first gear to second on the way home.

It has been sitting for a while.

the fluid is good, no burnt smell, and only slightly discolored. In a functioning vehicle I would consider it good. It is not new, so (unless the seller changed the fluid with used fluid) I don't see issues there.

Advice?

Pour some diesel fuel in there... Hoppes #9?

Drive it like I stole it and fix what breaks?

 

It turns out that once it got up to operating temperature, the blockage (or whatever) cleared itself.

Sliding right through the gears now.

 

You probably had a sticking spool in the valve body. I'd probably change the fluid and filter.