vibration question

summary---fine buzzing vibration in floor/peddles mostly related to load with no clunk/shudder/noise/ after work done to replace needle bearing.

2011 Tacoma 4x4 DCLB with 90,000 miles. 2.5 spacer lift front, 2 block rear. 285/70R17 Cooper AT3

got the truck used from dealer with 81,000 miles.

put lift on at 82,000 miles

worked out balance and alignment issues at 82,000 mile (Road force balance and good alignment shop)

I was very happy with the feel of the truck all through summer. About 3 weeks ago I started to get a vibration that felt like a fine rumble. I could feel it in the floor/peddles/seat and wheel. It went away in 4HI so it was the needle bearing on front diff. I took it back to the dealer because I had a 12 month limited warranty. They fixed the issue by replacing the needle bearing (not a great solution but it was warranty). I got it back and that vibration was gone.... but...

diff leaked at the seal and I felt a different issue. A very fine buzzing type vibration. I did not think much about the vibration as I had a leak to deal with. took it back to the dealer and a new seal was put on (this time in the proper place). The leak is gone... but...

the vibration is there, annoying and new.

I have yet to pinpoint the vibration. here is what I know.

it is in the floor/peddles mostly. I do not ever feel it in the seat and very rarely in the steering wheel.
it is a very fine buzzing type vibration. there is no shudder, no clunk just a fine vibrating pad type vibration.
seems to not be speed related (anywhere from 10 to 75), more rpm/gear/load related. I am now thinking rpm/gear do not have anything to do with it and it is load.
it shows up under load mostly. it is not fixed with switching into 4HI. Turning left or right does not seem to make a difference.
it goes away when load is light (cruise and going down hill). when it shows up is tougher. there are times when I think I am imagining things and there I times when I am sure my truck is falling apart.

I have read dozens of articles on vibrations and watched a bunch of youtube videos, nothing is exactly my issue. I began to think it was U joints but everyone with bad u joints indicated that had a shudder along with a vibration, I do not. I do not believe it is a wheel bearing based on symptoms (noise and change when turning).

I took it to the dealer yesterday and he felt it but it was not really acting up and he/I attributed it to normal for a truck.

Here is the odd stuff.

it was not there before the needle bearing diff issue.
it did not show up until the work was done on the drivers side front end (taking the shaft out twice).
it does not seem to adhere to any typical vibration issues
it showed up 4 months and 6K miles AFTER my lift.

why did this show up now after work done on needle bearing? could it be a coincidence? is it one or more U joints going bad in the drive shaft and just happened to show up at the exact time the needle bearing crapped out? could it be related to the work done on the needle bearing like something broken or loose?

I have been trying to convince myself it was always there and I am just to fixated on vibrations at the moment but I do not believe that to be the case.

Any info thoughts would be great. I am leaning toward a rotten coincidence that needle bearing and 1/more U joints decided to fail at the same time but not sure.

Carl