Bad vibration in 1st gear...have tried everything to fix it

my truck is a 2006 dcab V6 4x4 with 191,000 miles. I have spent over two grand trying to fix this vibration problem that no one seems to know what it is. The problem occurs when under acceleration in first gear the more load or higher you rev it out, the worse the vibration gets. So far they have rebuilt my rear end, replaced the u joints, carrier bearing, got the tsb leafs. I have done all this within the past month. I do have the bilsteins set at .85 in the front but pretty sure I had those for a while set at that without this problem and I'm sure the rake is now set back to how it was when I had them without the tsb leafs. It definitely vibrates from the rear end and feels like some sort of drive line issue. I have no idea what else to try. It gets pretty bad if you stomp on the gas it feels like something is almost slipping internally. Have any idea what this can be? I have spent a lot of money trying to fix this and the truck drives the exact same now as it did before. Before getting the tsb leafs I was hoping it was axle wrap, but I guess that was not the issue. The vibration is still there

 

Any help would be greatly appreciated because I have to leave to go back to school soon and won't be able to get it fixed for a while

 

I just got an 06 taco access cab, with 130k km on it, and I noticed that just a little. Mine is very minor, and the truck is in very good condition overall.

I had one Toyota customer service guy tell me that it was not uncommon, and is worse on the access cab compared to double. He said it's just a minor imbalance in the drivetrain, nothing to worry about. But now the you're saying you have one that's bad, I'm concerned. Wonder if it's gonna get worse.....

Did your vibration start off barely noticeable and get worse? Or just show up one day?

 

It got worse as time went on but I actually just completely fixed it last night...I flipped the carrier bearing 180 degrees and it seemed to be the issue for mine. Really sucks I had to spend all that money on that other stuff that was probably completely unnecessary. Mine was a very noticeable vibration though right after take off then it would just go away. It would do it about 5-10mph for a moment then it was gone. I don't think anything bad can come out of flipping the carrier bearing.

 

By the way it took about 5 mins to flip it. Very easy to do, you may want to give it a they but yours could be caused by something different because from what I have read there are multiple things that cause it for some people, it's just like you have to experiment with it and figure out what it is.