I have noticed that my transmission housing has some very fine surface cracks in the casting. Sort of a spider web appearance in a couple of places on the housing. You can feel these cracks if you run your fingernails over them. Is this just normal casting appearance or something to be concerned about ?

 

Could be... hard to say without seeing... they are artifacts left from the way the molten aluminum flows into the tool during die casting of the housing. If in a spider web, the center of the web may be the sprue where the molten metal is injected, or where the eject pins push the cooled part out of the tool. The surface cools quicker, being in contact with the metal tool, formin these little "cracks". They are normal and are closely watched as part of the manufacturing process to assure the tool and process is performing well.

They could also be machine tooling marks in the mold itself, which is imparted to the housing's finish; but that would look pretty obvious.

BuddyWh