Contacted the dealer last night and they were finishing up installing 2 new rear axles and a new differential. Emailed them this morning to find out how the road test went and was told the rumble/vibration was still present and they would need to keep the car longer.
The car history doesn't really show anything related to this issue.
1-8-08 Removed switch and reinstalled in correct direction. Replaced light socket and fuse
12-15-08 Replaced roof antenna
6-17-09 Broken vac hose and lighter tabs, replaced steering wheel, headliner clips
8-17-09 Replaced clips on sunshade
10-13-10 Check engine light goes on/off remove and replace thermostat, fuel gauge reading incorrectly remove and replace right tank sensor
2-15-11 Car not driving smooth, jerky transmission shifting reprogrammed transmission
7-29-12 Car surges no problem or codes found. Howling noise replaced wheel bearing, valve ticking noise replaced valve lifters and rockers
At this point I am only communicating by email because I want a documented trail of breadcrumbs. My last email pointed out we may need to look at other options and left it open to them to respond.