It's not stupid question
Gearboxes are usualy made by:
1. gearbox specialists (companies that specialize in making transmissions)
2. engine manufacturers
3. some teams have made their own gearboxes (usually in cooperation with some gearbox specialist or with engine manufacturer or both).
Finally there is 4th option when engine manufacturer orders transmission from gearbox specialist and/or makes it together with gearbox specialist.
gearbox specialists: Hewland, Weismann, ZF…
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Too many "gearbox specialists" for one post
