I was busy these days making some transmission mods, and the main problem was making a proper differential ratios for each gearbox... I decided to leave it to players, because this is the main part of custimizing the transmission - and here I'm going to tell you how to choose your differential ratio and apply it to the game. I hope you will find it helpful enough!
First of all, what is a transmission? To put it simple, it is a box of gears (that is why it is also called gearbox) which transfers the rotation from engine to the axle, where it meets the differential, through which the rotation is transferred to the wheels, which makes your car move. But an engine makes too many rounds per minute (RPM), for trucks it can be up to 2500 rpm (and sometimes more). That is why we reduce the RPM twice before transferring it to the wheels. Firstly - at the gearbox, secondly - at the differential. And our goal, as drivers who customize their trucks, is to find our perfect transmission and diferential ratio.
Let's begin with the transmission. It has several gears (there can be 3 gears, 10, 20, 24... any quantity, but for now it does not matter much). Each gear has it's ratio, which shows us how much it reduces the RPM. For example, if the gear ratio is the 10.0, it means that the engine will spin the shaft 10 times, while the final shaft of gearbox is spinned only once. That is why it is 10. Furthemore, if the gear ratio is 1, the both shafts spin at the same time - without reduction. These gears with the ratio of 1 are called "direct gears". They are commonly seen as the last gear of transmission. Also, sometimes there are gears with the ratio lower than 1. For example - 0.7, it means that the transmission shaft spins even faster that the engine (but still reduced at the differential). These gears are called "overdrive gears". And transmission with these gears can be called the same way.
Now we know about gears, let's talk about the "total reduction". This is quite simple but important constant which tells us how many spins make a wheel at a single spin of the engine. For example, if the total reduction is 30, it means the wheel will spin 30 times during a single spin of the engine. This value helps comparing different transmissions with different differentials. It is calculated easily: just multiply your gear ratio by the differential ratio. It is mostly used when comparing first or last gears. For instance, let's try comparing the last gears of the 10 and 13 speeders. The first one has the 1.0 last gear and 2.85 differential ratio, while the second has 0.73 overdrive gear and 3.55 differential ratio. 2.85*1.0 = 2.85 and 3.55*0.73 = 2.59. As we can see, the 13-speeder has lower reduction on the last gear, which means - the truck will reach higher speeds at the same engine RPM.
That's it - the lower the reduction on the last gear, the more speed you will get. But keep in mind - the lower reduction on the first gear means slower launch and acceleration. It can be critical when launching uphill with a heavy load. It tells us that... "a perfect transmission" has a very high reduction of the first gear and very low one on the last.
It leads us to the next thing - overall ratio. It shows us the difference between the first and the last gears of transmission. So, yes, the more it is, the more universal the transmission is. To calculate it, simply divide the first gear ratio by the last gear ratio. The gotten number tells you how many time the first gear is faster. It can be presented as a coefficient or as a percentage (just coefficient*100%). Usually, for modern trucks, 1000% is too little, while 2000% is good enough for any needs.
So, how do we use this information on deciding about the differential ratio? The crucial formula is very simple: the less the ratio - the more speed you get, the higher the ratio - the better launch you get. You only need to find a perfect ratio for your purposes. The heavier your cargoes are - the higher your differential ratio should be. And one more simple formula: the low differential ratios and powerful engines are friends, while the high differential ratios and low power engines are friends too. Also.. a good way to find a perfect ratio is to test different ones. And now you know where you should look for the balance.
Here are some popular differential ratios of modern trucks:
Code: Select all
2.64
2.85
3.08
3.25
3.55
3.70
3.91
4.10
4.30
4.56
Actually, you can use any ratio which comes to your mind, but it would barely be realistic.. but it's always up to you.
Applying the differential ratio into your transmission is quite easy. Open your truck mod archive (if you want to change the SCS files, unpack their archives and re-pack them as a separate mod with applied settings of yours). Go to:
Code: Select all
def/vehicle/truck/(truck name)/transmissionCode: Select all
differential_ratio: 4.10(it can be any other number, this is just an example)
All you need is to change this number to your wanted differential ratio. Make sure you use dot, not comma.
I guess.. that's all I wanted to tell you. If you still have any question - post it here and I will help as soon as possible. (Also.. did I miss something? Let me know if so)
Thank you for your attention!
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