I've been chasing this same vibration without success. I replaced every bushing on the diff and mine was in worse condition than the one pictured. It made no difference. Next up I'll be pulling my driveshafts one by one to see if that makes any difference.
Hey ya'll I've been chasing an alignment issue as I've been baselining my 2001 hundy with 235k miles for several months now. She pulls slightly to the right, but VERY consistently. I drive a lot of hwy miles and it drives me crazy always having to correct the steering.
Most recent alignment...
You still have the steering wheel and interior rearview mirror?
Edit: Forgot to ask if you've got the tool kit as well (looking for the spare lock key)