I needed to lock the differential today, but this is what I found. Any ideas on why I'm looking at what I'm looking at? Is this a 2003 case by some chance?

Original issue was U-joints on front shaft shot, replaced them, but now I have a very high frequency vibration from about 15mph. The drive shaft pieces orientation was marked and kept in reassembly.

Am I looking at having to replace the t-case to get diff lock back so I could drive one rear shaft if I had to?

 

Yep! No diff lock there.

You could replace the whole transfer case, or just the front output housing from a suitable donor truck. Talk to Paul Grant, he sold me one a coupla years ago.

 

That's a bummer. Looks like the t-case was replaced with one from a mid-'01 to an '03.

 

Major bummer. I have to drive a few hundred miles on a driveshaft that is vibrating my spine out of me on NEW U-joints.

 

Did you rebalance the shaft? You don't mention if you've ruled that out.

 

Nope, I've never had to do that before when the relationship of all the parts was kept proper. I will be taking the shaft to a driveshaft shop next week to get the balance checked out.

 

OK so you replaced the U-joints yourself then... On the original shaft? You don't mention if you also replaced the center ball...

Often sudden symptoms are related to recent work.