My Duster is under the knife....TKX going in

Hmm. Weird. Any vibrations, howling or wines? Wonder if the blocks are loose? Removing them could narrow things down any way.
If something was loose at the diff I would think there would be noise going down the road?
Hopefully it's a simple. Maybe something in the differential is sticking?
The subframe connectors should be nice as Hotchkis makes a nice product. Unrelated to the issue.
How does the the clutch pedal feel? I have the same set up as you but I am several months away from trying it out? What gear ratio?
Excited to see how this goes. I am on the same road just not as far. LOL
Hopefully it's just the cone in the differential sticking a bit. I'm going to take it out for a longer ride today and see if frees up a bit. I'll try what Rusty (see above post) recommends. No howling or other noise.

As for the transmission and clutch, I could not be happier. The transmission "guides" the shifter right through the gears with precision. Down shifting is a breeze too. The clutch pedal is nice and firm, but once depressed, I can keep it depressed without undue strain on my leg. The release point is about 1/2 way through the travel. I have 3:23 gears and can now go down the interstate at 75mph at 2000rpm. I chose the "close ratio" gears for the Tremec as I wanted smooth shift transission between gears. So shifting from first to second comes fairly quick from a standing start.