2007 Tacoma

My new truck has a problem that Toyota acknowledges, but doesn't know how to fix it. So they say it is typical but not normal. (?) So I thought that you might have a suggestion.
The truck has a vibration/shudder when it shifts gears up or down and is most noticable when slowing at 25MPH until about 10MPH and sometimes all the way down to zero and continues at idle. It seems to be getting worse. When I drive thru the neighborhood at 20 - 25 MPH, the virbation continues and feels like I'm driving over small rumble strips. The truck has 7,500 miles and I first noticed it about a week after I bought it - don't know if it was there originally or not.
The Toyota regional guy recorded the symptoms and sent the data to HQ - says they wonder (?) If it is in the torque converter.
The truck is 4.0L Auto 4x4 & problem occurs in 2 or 4 wheel drive. Tires/wheels have been ruled out.
What is your best guess? Thanks so much.
Mike Titus