Thought this was cool...


https://www.youtube.com/watch?v=IKywZ730JFs#at=191

I finally "got" how this setup works by playing with my "Lego Super Car", which had a four-speed transmission built in. Seeing all of the bits work, and not just the parts that are visible from the outside, helped a lot.

--DD

Okay, I'll bite the bullet and be the first one to admit it. Transmissions are still a mystery to me. I understand the flow of power and the purpose of each component, but until I tear one apart, I can't see how the shift fork moving the synchro and hub assembly forward actually engages the next gear.

But cool video!

The gears have the regular teeth on the "edges". They also have a few teeth on the "front face", basically sticking out 90 degrees from the circle part of the gear. The slider has similar teeth on the end of it; when you push the slider toward the gear, the teeth on the end of the slider mesh with the teeth on the face of the gear.

Make sense?

--DD

Sure. It all makes sense. I still don't fuchin' understand it but it all makes sense.

OK, I'm going to try showing this with pictures, then.

First, one of the gears that transmits the power:
http://rebrickable.com/parts/6542

Ignore the teeth on the one face, when the image rotates around to show you the inside, look for the triangle-shaped teeth on the inside. Also notice how the inner part of the gear is smooth, so it does not grab the shaft it is riding on. It just slides over it, so the shaft can stay still while the gear spins.

Next, the slider:
http://rebrickable.com/parts/6539

Note that it has splines on the inside, so it rotates with the shaft it is on. And the teeth it has on the front and rear ends will catch on the teeth on the inside of the gear above. When they do that, the gear is now locked to this slider, which is locked to the shaft by the splines.

All of the other gears, though, are still freely-spinning on the shaft. They aren't locked to the shaft at all! (Unless you slide one of their sliders too, in which case the shafts stop turning because they are trying to turn at two different speeds at the same time!)


The sliders are in grey in the following picture instead of red, so they're a little harder to see. But the gear shift lever (the part with the blue cone on top) has a flat end that can push the slider forward or back, and have the slider engage the gear to its front or to its rear.





I hope this helps make some sense out of how that thing works!

Oh, speaking of "how stuff works", here is their article explaining it:
http://www.howstuffworks.com/transmission.htm


--DD

Awesome narrator.

Very cool!,, still not ready to open one though.
As long as we are on the subject dose any one have any idea what would this Audi/VW code EZG series 012 transaxel do for you with a 2.0 4cyl in a 914?

Very cool! I never really understood how a tranny works, but this is a great illustration.

This page and the next one after it finally made this make sense to me. I didn't see the small gears on the output shaft before. Now I see when the fork moves over a gear how it's locked into the power coming from the input.

http://auto.howstuffworks.com/transmission4.htm

I can see this. The part that is confusing is EVERYTHING keeps moving? Or do these other gears kinda just freewheel dangle like?