Lurching problem and I'm out of ideas.

Bad Sport said
If you get a chance do the coast thing again in neutral first and see if it does it.

How long ago was it rebuilt? Have you checked the diff fluid? Something inexpensive you could try, is to put some friction modifier in the diff. I don't know if it will help, but if it doesn't have or have enough modifier in it it might give you that lurchy feeling. Again, it's just a guess but something you can try that doesn't cost an arm and leg.

I know when I rebuilt my center section it felt like a spool when turning for a bit, catch and release catch and release.

Thank you for the help Bad Sport!
I'll do the coast-neutral test again today, the annoying part is I have to drive around for a long while before it starts happening.

About two years ago I purchased it from a yard that 'rebuilt it' and it immediately it was whining. So I took it back and they 'rebuilt it' again but it still whined. And they said it was "really hard to get right", which made me wonder if I was going to the right people... I've changed out the fluid and added Mopar friction modifier since. The first fluid change was very dark but I just crossed my fingers that was a break-in thing.

All that said, I haven't done an oil/lsd fluid change since the issue started occurring so I'll take another look at the oil.

Is this a potential issue for both spool and clutch type suregrips? Or just clutch?