Most car manufacturers do not. For instance, how many of them do their own ECUs? And large swaths of the American car industry have long been defined by outsourcing relationships. Remember Delphi?
True. Being around Detroit you can see the entire industry that supports the "Big Three". There are companies that either supply or assist in the build of nearly every component of a car.
I immediately thought of Delphi as well, but there are also numerous other counter-examples to the grandparent post. For example, I had a Plymouth in the 90's with an engine built in collaboration with Mitsubishi.
Of course that kind of thing happens. Honda had a V6 engine with mitsubishi in their accord too, but the typical behavior is to do most things in house, not all things all the time.
Indeed. Ever owned a European car? Heard of Bosch?
Ever owned a Japanese car? Heard of (Nippon-)Denso?
You would be astonished how many bits of a car is subcontracted. What the auto manufacturer typically focuses on is engine design (at the mechanical level), chassis design and suspension topology. Most things that "bolt on" are made by somebody else.
