thanks so much for the welcome. I'm a mechanic that owns a transmission shop. It's coming through the steering wheel, don't feel it anywhere else. Yes, when you let off the gas then hit the gas again, it usually starts again. Transmission was rebuilt 2 days ago and the axles were replaced today. About 10 minutes ago, I just took out the rear drive shaft, plugged the transfer case and drove it, no more vibration. However, if it was the drive shaft itself it should vibrate continuously, not only at 30-40mph. I am leaning towards something in the rear differential or the AWD unit. Any ideas?
(this is actually the wife/secretary doing the posting, he hates typing Thanks again for the welcome and for any ideas or insight)