eli5 Why don’t all transmissions have dog gears if you don’t need to use clutch while shifting them?

Question

eli5 Why don’t all transmissions have dog gears if you don’t need to use clutch while shifting them?

In: 1

Answer 1

Just because *you* aren’t actuating a clutch doesn’t mean there’s no clutch…it just means the transmission is controlling the clutch(s). All transmissions except direct drive have some kind of clutch.

Clutching isn’t why you do/don’t use “dog gears” though. I assume you mean straight cut gears, “dogs” usually refers to a particular clutch design. We tend not to use straight gears in a lot of auto transmissions because helicals are a lot smoother and quieter. We don’t use dog clutches in a lot of cases because dog clutches don’t engage with large speed differences, which we sometimes need. Transmissions with dog clutches (most manuals) use synchronizers (usually cone clutches) to match speeds before the dog clutches engage.