After a second trip to the dealer, I have nothing constructive to add. The first trip was for my 15K service on Saturday, but they didn't have a tranny expert on site to diagnose the problem. I brought it back today and the tech hooked it up to his computer. All of the line pressures were within spec, and no error codes were displayed. I took a ride with him and then I drove for a while trying to duplicate the thunk. It wouldn't do it! The tech concluded that there was nothing wrong with the transmission and what I was feeling was rear axle wind-up. Doesn't the VX rear suspension design preclude this from happening? He did confess that the Trooper had a problem with binding drive shafts, but the VX has a different design that doesn't bind. He did shoot some grease into the shaft while he had it on the lift, but said the grease that squirted out was still good. I greased it at 7500 miles and asked if I had possibly used the wrong type of grease. He said it was OK. SOOOOO... Until someone can come up with an Isuzu recall or TSB there's nothing he can do. At least I have it documented.