Double Clutching and Heel and Toe – The Constant Mesh Gearbox – How to drive a Classic Fiat 500 – Howtoshtab – how to, lifehacks, tips and tricks

Hi guys and welcome! Today I’m going to teach you all about the gearbox in the 500. There’s going to be some driving and some theory. If you pay attention you’re going to be able to drive the 500 like a pro… Stay tuned. Let’s go drive. You might have noticed that shifting gears, especially downshifting is pretty tricky and the reason is the 500 has a constant mesh gearbox. Before we proceed any further, let me explain to you how a constant mesh gearbox works. This is a simplified representation of a constant mesh gearbox.

It’s called constant mesh because all the gears are meshed together all the time. We have basically two shafts: the lay shaft which is the input shaft, that is connected to the engine when the clutch is engaged and we have the main shaft which is the output shaft transferring the power from the engine to the differential and wheels. On these two shafts we have gears the gears on the lay shaft are fixed to it while the gears on the main shaft are on bearings and can spin freely on the shaft. When the clutch is engaged, all these gears spin together with the engine, but the main shaft is connected to the wheels and when the car still is not moving at all. To engage the gears we have dog clutches. the dog clutches are fixed to the main shaft (that is splined), while the gears are bearings. The dog clutches rotate with the shaft and can slide back and forth to engage the gears. You see, they have teeth on the sides and the gears have teeth on the sides and when the teeth interconnect the gear spins the shaft. So when you slide the dog clutch and you engage your gear, the power gets transferred from the engine through the clutch to the clutch gear to the lay shaft to the gear on the main shaft and to the main shaft into the wheels.

You connect the engine to the wheels basically In neutral with the clutch disengaged, you can just put any gear in no problem. When the car is still and the clutch is disengaged the lay shaft is not moving because it’s disengaged from the engine, and since the wheels are not moving the main shaft is not moving either so you can engage any gear with no problem once you’re moving though you will have the problem of shifting gears, because every time you disengage your gear you will have the main shaft and the lay shaft spinning at different speeds. Thus the gears are going to spin at a certain speed, and the dog clutches at a different speed. So, the only way to connect the dog clutch to the gear is that the teeth are rotating at a compatible speed of course First. Into second into third and into fourth No problem, right? Well, there is a secret to it.

Since you’re going from a larger gear to a smaller gear, the smaller gear is going to be turning faster when you disengage the clutch, the lay shaft slows down a little bit, at that point the dock latch is compatible with the gear so provided you don’t wait too long or too little when shifting gears, you can just shift from one gear to the next with no problem. Let me show you again! Clutch and waaaaait and when it wants to go in, it goes in. third fourth. The secret is you want to finesse the gears in, you don’t yank them. you don’t push them in. Just slowly try to engage the gear until it just pops in. If you try to yank them like you see some people shifting on Youtube, you’re going to break your gearbox. So, don’t do that! now imagine that the car is in neutral, going 60 km/h what happens is: the engine is making the lay shaft spin at idle and the wheels are actually dragging the main shaft at 60 kilometers per hour, so the gears and the dog clutches are all spinning at different speeds. What you need to do now to engage a gear is match the revs of the dog clutches and the gear you want to engage.

What you really want to do when you want to learn how to drive the 500, is get the feeling for the rev matching. To do that you go at the certain speed, put the car in neutral, and based on the speed you’re going you try to put the gear in. Now I’m going 50 in 4th put it into neutral. Now I’m in no gear watsoever. I want to put it in 3rd so, now I’m going 55, I want to put it in 3rd, I accelerate and then put the gear in. When you practice like that you need to know what gear to put the car in. To do that you use the red lines on the speedometer. The red lines on the speedometer not only tell you which gear you need to put in but they also give you a rough idea of how much you need to blip it. Let me explain that on the whiteboard.

The red lines on the speedometer tell you when you need to upshift so they kind of represent the hypothetical red line in the rev counter you don’t have in the car. This way you kind of know the range of each gear. So let’s imagine the red line is at 4k rpm which should be pretty accurate. So for each speed you will know which gears you can engage and at what rpm so let’s say we are going 60 in neutral we will know that that represents 3.5 K rpm in third or roughly 2.5 k rpm in fourth. Let’s say you are going 20 you’ll know it’s 3 K rpm in first 2k rpm in second and so on of course you will still need to do it by ear but that’s good to know. Now I’m going 60, I cannot put second in, I can only put fourth or third… to put 3rd I have to blip it a lot like this or to put 4th I have to blip it much less Of course I was going uphill, so car was slowing down.

Let’s try again I’m going 60, put it in neutral, blip it a little, 4th gear, no problem let’s try on a slower speed. Now we are going thirty-five 35 now see? Let’s try again, neutral, now we are going 40, so healty blip, put into gear in second. Brake a little, going 40 again, blip it. Second! Going 35, blip it a little less, second gear. Going 60, third gear. Now there’s a uphill, I put it in neutral, car is slowing down, slowing down slowing down. I’m going 50, accelerate a little less, and put it into gear. Now I’m going 35, put it into second! Once you get a grip with the rev matching, you’re ready to start with the downshifting. As you are going from a smaller gear to a larger gear, the larger gear is going to be spinning slower and the dog clutche is going to be spinning faster. The technique you use to downshift is called double clutching. And that’s how it works: you disengage the gear, you brake, you accelerate in neutral and then put in another gear so you clutch twice, once to get the gear out and then you engage the clutch again in neutral, and then when you want to put the gear in again.

So you clutch and disengage the gear then you engage the clutch in neutral thus connecting the engine to the lay shaft, at that point you accelerate, you transmit the power to the gears and you make the gear you want to engage spin faster so that it is compatible with the speed of the dog clutch and the teeth can interconnect the way you learn how to do it is: you’re in 3rd, you brake you brake you brake and now you are in the range of second gear, you disengage and you put in second. You need to get ready a little bit in advance, so you know there is a turn, so you brake and when you’re in the correct range, you just put it into gear. You brake, correct range, put it into gear Once you get a grip with all the matching the double clutching etc you can start to think about heel-and-toe. heel-and-toe is a technique in which you do the braking and the double clutching at the same time. As you are on the brake put the car in neutral, then revv it, and then put it into gear again.

So this time your right foot doesn’t need to go on the brake and then on the accelerator and then on the brake again eventually, but it can just do both things at the same time. 3rd gear. Heel-and-toe: brake, neutral, accelerate and go. Brake, neutral, accelerate and put it into gear. when you master the heel-and-toe even the 500 doesn’t feel that slow anymore, because you can keep everything optimal and you’re going to be ready to get out of the turn faster. Oh let’s heel-and-toe twice! 3rd gear, 2nd gear, when you get a grip with it, it’s very easy. If you think about it, this car was the most common car in the 60’s in Italy, and everyone was driving it. You’ll get a hang with it and you’ll be able to heel-and-toe like a pro. Starting of course is like any manual car. While in a normal manual car when you’re going so slow that you’re almost stopped you can put in the first year, in this car you cannot, you need to put in second. It’s no big deal, the gears are very short. 1st gear should only be used when you are still and just to start. A little trick to make the double clutching easier, is that the shape of the teeth on the dog clutches and the gears are so that when you release the accelerator abruptly and you very quickly disengage the gear, it just disengages without clutching.

So at this point you’re in neutral with a clutch engaged. Many people are swapping the gearbox with the synchromesh one like the one in the 126 or the 500 R. But I just think beside the originality aspect, which is important to me, there is also the fun factor that the constant mesh gearbox has. I mean, the 500 is pretty slow, but it’s a lot of fun when you have a non-synchronized gearbox because you have so much more to do to. It will make you feel like you’re a better driver, and it will actually make you a better driver if you master the constant mesh. So in my opinion constant mesh is more fun and it doesn’t have any downside. I used to daily drive this car and I actually have a lot of fun with it, so why would you change? Actually what I’m thinking about is we should get a modern car and that the gearbox rebuilt with no synchronizers and see how much more fun that is! bye guys! you.

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