@duerer maybe you went a bit overboard with the shrinkwrapping on the gearbox; nine(!) separate Shrinkwraps?
Doesn’t that defeat the purpose of shrinkwrapping? You want to make it look like it’s one piece and by shrinkwrapping different parts to different Objects you are asking for trouble;)
What you might be able to do, is use this object, with all of its Modifiers and use that as a Shrinkwrap object for a duplicate of it without the Modifiers…Then place a Subsurf before (with as little subdivision levels as possible) and after the Shrinkwrap (of this duplicate gearbox) where needed and apply the Shrinkwrap (and the Subsurf that comes before it, of course).
Personally I’d get rid of all the Shrinkwrap Modifiers, do some topology cleanup and then maybe shrinkwrap part of the gearbox to a Cylinder if necessary. Most, if not all of those ‘sticking-out-parts’ won’t need to be shrinkwrapped, I think.
