Harmonic Vibration 20-30mph &60-75mph

I have a 2007 Prerunner SR5. Ran smooth for years. Did a 3 inch lift about 3 years ago and 1 year ago vibration started. happens at 20 -30 mph and then again @60-75mph. Does not happen in neutral at those speeds and less when foot off gas.(First go around) Had shaft balanced with new carrier bearing installed and shimmed for alignment along with all new U joints.That cost $1,000,Did not solve problem....
(Second go around) Had a second mechanic take rear differential apart and inspected but no problems detected and had shaft balanced again to make sure it was balanced correctly. All this work the second time was done by a reputable 4 wheel drive "lift expert" group.(Another $1,000) Still have vibration issues and its very annoying especially when it never use to do this and I'm $2,000 into it with NO answers.... I have a hard time believing its transmission since shifting is perfect. I have to think it is some type of trans mount or something along that line? OR will a new single shaft resolve problem so to get rid of silly carrier bearing all together???? How could it be tires if it does not happen in neutral ???? It has Firestone Destination AT's which have reputation for problems, BUT no vibration at these speeds in neutral so how could it be tire related??? HELP!!!!!!!! Someone has to know whats going on here???

 

check out this thread

http://www.tacomaworld.com/forum/2n...nt-differential-bearing-vibration-thread.html

Basically the driver front needle bearing sucks, and becomes apparent after doing lifts. Put your truck in 4x4 mode and see if the vibration is still there at 30-40mph. If it goes away or is barely noticeable its probably your problem.

Contact ECGS and get the bushing the created to solve this issue. Cool guys over there.

 

Its only 2 whl. drive.... Does that change anything with what your saying?

 

The needle bearing is a problem on 4x4 only.