The 205 is spec'd for both AT and gear lube, depending where you look. I would use only gear lube myself since it is a gear set just like a diff.
The 205 and 203 are both cast cases and heavy!
This pic shows the easiest way to identify a 205 (round cover in the middle). The tcase shifter knob is another way of identifing between a 203 and 205, they have different patterns:
http://www.akfabshop.com/alaskaoffroad/ ... /205_a.jpg
http://www.offroaddesign.com/catalog/Tr ... 0Guide.htm
To the OP, i can run my truck up to 80mph in 4x4 with minimal vibration. All joints have to be in great shape though. I had problems with the front driveshaft to tcase mating bolts coming loose for sometime, finally used some blue loctite and they are no longer a problem.