To my surprise reinstalling my original transfer case with new bearings and seals did help to reduce vibration compared to the salvage yard transfer case that received the same treatment. Mine is in much better shape and felt smoother on the bench even. Maybe 40-50% less both under power and coast. Most notably when coasting from say 70mph it would start to vibrate some in the seat and floor, then if I hit the brakes to drop to 40mph for an exit ramp I could really feel it in the brake pedal. The brake pedal vibration is gone or mostly, it might just be in my head if it still exists. Once I get down to 35mph or less there's no wheel speed vibration.
Tasca has for the 2nd order in a row cancelled my order due to being out of stock, though they still show the part in stock, argh. This time for the rear diff torque arm, they show 26 in stock. My wife just went to local dealer and paid an extra $50, total $205 including the governor's share. They always charge MSRP or higher, but it'll be available tomorrow. I'll get that installed this weekend and see how much the new bushing holding the diff firmly helps.
Still have some engine speed vibration I'm tracking down. A new fan clutch has been installed, not sure that helped the engine speed vibration. It is certainly tighter. All I did was run it in the garage though.
Maybe someday I'll get all of the causes of the vibration figured out. I got most of this resolved a while back when I replaced the rear cv axles and hubs. Not all of it though and it clearly snowballed while it was being ignored until it just got to be too much for me tolerate any longer.
When I get done I'll compile a list of the things I replaced, adjusted etc...
