The following information is based on my current research and the game's state. Stormworks is still very much in development and the engine/gearbox/wheel behaviour is currently NOT optimal and very likely to change. I'll try to keep this updated.

A short revision

So, how do gearboxes work again? What do they do?
Well they are needed to make combustion engines effective, they are used to balance the engine's power output between torque (basically force to move it self and important for acceleration) and rps (which influences top speed and fuel consumption)

They have 2 internal options (using the select tool): Ratio 1 and Ratio 2. Upon feeding it with it's "Gear Switch" Input, it will switch to Ratio 2.
The Ratios are by default always A:B, A being the smaller number, B the bigger one (1:3 / A:B)

Now let's understand these ratios here:
What does 1:2 mean? Basically: For everyone 1 rotation entering the gearbox, 2 rotations come out, however in exchange for less torque.
Now, if you invert the direction of the gearbox, the Ratio is being swapped around, basically it's now B:A, so now ratios like 3:1 are possible

Here's a good illustration:
If you want to figure out which way they have to be turned, just look at the arrows: the smaller tip of the arrow is always the smaller ratio part (by default: A), while the bigger part of the arrow is obviously the bigger part of the ratio.

Assuming the engine would be on the left side of the image and the wheels on the right side, then the top gearbox would have a Ratio of A:B, because the arrows point towards the engine.
The other way around goes for gearbox #2 on the bottom.

A 1:3 ratio would give you the highest top speed, but a low torque, meaning the engine really struggles to accelerate
A 3:1 ratio would make your car quite slow, however it should now be able to pull heavy loads.

Enough of that.

They are equally important and not in any particular order!

Only use as few gearboxes as needed. 4-5 is enough in most cases. They have an efficiency of 95%, so the more gearboxes you have, the less efficient they are. Calculate the efficieny using 95%^N. N being the number of gearboxes. Say 10 gearboxes would mean 95%^10, which is around 60% total efficiency.

You should spread your gearbox ratios as far apart as possible:
These are all the gear ratios a single gearbox can have (both way around). Say you want to build a transmission with 4 forward gearboxes (+1 for reverse). Here's how you should distribute them
This is required for better ratio calculations, in order to max out the possibilities.

And example for this using all the possbile gear box ratios on the game for building an easy 5 gear transmission (without combining):

A ratio of 1:3 is good for high speeds, but if you add 4 gearboxes with a 1:3 ratio and activate them all at the time, the engine is just overstressed and isn't effective at all. It will probably not even reach a high speed, since it can't get the rps up at all. Mess around the final ratio (the ratio of your last gear) should be around 1:3 to 1:9 usually, but somtimes higher values make the top speed even worse, as the torque is too low in order to get the speed up.
In the other direction: 9:1 as first gear is so unbearably slow and unless you plan to pull a huge tanke or airplane with your toyota prius, it's not necessary at all. 3:1 or 2:1 for first gear are usually fine.

Using 1 gearbox at a time might be neat and simple but if you combine multiple ones (activate more than 1 at a time) you can archive far more possible gear ratios than before (just read on, I'll explain it later)

Have a well-cooled engine, use tires with the highest possible speed and most importantly: KEEP THE MASS LOW. It's one of the most influencial factors. The more mass, the slower you are.
ALSO: Size/Aerodynamics are important.
From the Stormworks issue board[mcro.org]:

引用自 Charlza：

The low top speed of your car is most likely due to the massive amount of air resistance their is in the game. Its like the air is made of water (and the water is like crude oil). It's a really common things in games like this (...) as it makes everything easier to control.

If you are unsure of what's limiting your top speed: Upgrade the engine. Maybe go for a compact jet engine, since it will probably bring you the most power, if you still reach the same speed, it's likely due to the air resistance.

If you want to build an advanced gearbox, you might want to consider planing it first.
This is the most complicated part of the guide, it requires a bit of initital thinking, but once you get behind it, you're good to go.

You can use a lot of gearboxes in order to archive one possible gear for each, but doing it smartly will allow you to maximize the gearbox efficiency.

You remember the ratios.

Say you have a 1:2 gearbox and a 9:5 connected in a row. Well what would that output be?
Simply said : 9:10. How do you calculate that?
A1*A2 : B1*B2. Easy
1:3 * 3:1 would be a 3:3 ratios, which (as you most likely know) can be shortened to just 1:1.

Ok, simple enough? I always open a new file in notepad and do my calculations first in order to plan what I have to build.

You might want to calculate each ratio as 1:X first. So 5:9 will become 1:1.80 (divide both numbers by 5)

Because that's quite painful, I've already done these calculations, here they are:

I named them #a-#f for B:A ratios and #A-#F for A:B ratios.


These are the values I'll calculate with from now on.
Now you can start multiplying.
Say you have #D and #f on at the same time, the ratio would be 1:2 * 1:0.83 | The A part is 1*1 and will always be 1 using these converted values, so you only have to worry about B, which in this case is 2*0.83 = 1.66, so the final ratio is 1:1.66

Now let's do a clean example. We have 4 gearboxes (+1 for reverse) and want as many gears as possible. Just remember you can't combine them completly random, since they are activated and therefore no longer available or deactivated and available. Example if you have #F and #E activated as 5th gear, you can't just say for 6th gear, you will take gear 5 + gearbox #F, as #F is already in use. (Sorry for the bad explanation)

So, let's go:


I hope I made it clear enough, don't hestiate asking me questions.
(Ping me on Stormworks Discord @Momox#6997 )

So now you know the technical background, but one things is missing: How do you get it all to work?
You'll need a micocontroller for this. There are countless solutions on the workshop, however, I've also designed one for you. It's a semiautomatic ("paddleshift") transmission controller.

It features:
- Setting for lowest and highest gear
- A simple counter that always output whole numbers
- A clutch output to simulate actual shifting
- A Neutral gear
- Fairly easy to understand

(There are a few simple function blocks inside with just "x" as function. These are relays to make the structure easier to understand, you can remove those and fix the missing wiring.

Here's just the microcontoller:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1720305949

And here's the whole example of it, with a pilot seat and everything wired up.
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1720302358


NOTE:
There is definitely space for improvement. I've tried to keep it as simple as possible, but this is the core tech of my transmissions, I've been using the same clutch controller and gear counter system, just a bit more modified.
You are free to, if not encouraged to use it, modify it, upload it the way you want, I really don't care.

It should give you a rough idea of how a controller could work.

This is the end of the guide. I wanted to thank you for reading.
I did this in order to encourage building of new transmissions and to share knowledge. Feel free to ask, critize or improve what I did here.

Contact me on Discord if you have questions (please do so via the Stormworks Discord and not via friend request):
Momox#6997

Also, if you need another read on the matter: Steam User Ra-Ra-Rasputin made an awsome guide that goes more in-depth on how gearboxes actually work. I recommend you reading it, it's a very well-made guide:
LINK TO THE GUIDE