Anyone have any idea on original colors for the D18 and T90?

Hmmm... thanks alot for all the replies, guys. Gives me alot to think about and work with. Appreciate it!

 

MY BAD...NOT TRUE...

As a matter of fact the SM-1046 specifically designates D-225 head and block material as CAST IRON.
I seriously doubt if the transmission and transfer case mateiial was ever noted for service info.

Metal can be identified using several various methods.
Spark testing is usually a very accurate and it is a non destructive method.
I spark tested a transfer case front bearing cap and it is definately grey cast iron.

Thanks for correcting that one Duffer.

 

Yep, black if painted. Car makers hide the drivetrain under the car by painting everything black. They want people to focus on the shiny body, not on the chassis. Bare cast iron will rust, but typically it's coated by a combo of road grime and oil that prevents significant rusting. Surface rust is not considered a problem for cast iron parts, apparently.

What I've seen - the component manufacturers deliver the components either in bare iron or painted. As far as I can recall, chassis, axles and springs are painted black when built and no additional painting was done - ie, the chassis was built with parts in the condition delivered and no additional painting was done. Parts department trans and TC were both bare iron and black. Kinda think the Borg-Warner replacements came through with black gloss paint, and the Dana stuff came through bare. Steel component parts (not cast iron) were generally painted gloss or flat black, I assume for longer shelf life. Cast parts came through bare except for a cosmoline or oil coat, sometimes. Service blocks came through as bare iron, in plastic.