World's Best DCT. Porsche PDK. How it works........... Part 1.........

My goal at the end of this video is for you to know a lot more about the Porsche 7-speed pdk dual-clutch transmission that was installed in most Porsche sports cars from about 2008 to the present. It is not a video for mechanics but one. For the average car lover who just wants to learn, the video will be divided into numerous sections for each. I'll start with the basics and move on to some pretty technical details, but without going completely crazy, I'll use a lot of diagrams. and then for each section, I'll go to the stream to show you what it looks like in reality.

The full video will be quite long, so I have divided it into two

part

s. This first

part

will cover clutches and gears. The second part of the set will cover the electrical cooling and lubrication systems and the valve body, and by the end I hope you'll know a lot more about the magic that happens in the back of a Porsche sports car. First, a little background on what the PD K is like. A dual-clutch transmission made by ZF in Germany, it was initially installed on the 987 and 997 cars for the 2009 models and, although it had some minor changes, since it is basically the same transmission that is also fitted to the 981, 991 and 718.

Although ZF makes transmissions for many automakers, this dual-clutch transmission is licensed to Porsche only as a result of this, unlike most other transmissions made by ZF, there is very little information or parts available, so it has existed under secrecy for many years. many simple repairs, the porous solution is to buy a new transmission, an unnecessary waste of money and simply not necessary in the vast majority of cases, some will know that I have two 981s, one to drive and one to take apart as a learning tool and making videos to help others as part of this project Ted down, a very generous person from Sydney, Australia, contacted me and offered me a pdk transmission to take apart, as it had been damaged in an accident on the track, and Thus began another project that consisted of disassembling the transmission and making it. videos to provide as much information as possible to people who needed help with repairs.

I've been helping people and

works

hops for a while, but I thought I'd do something a little different, which is make a video for anyone interested to explain. How does this amazing piece of engineering work, so what is a dual clutch transmission? It is regularly described as a cross between a manual and an automatic transmission. The gear set is practically identical to a manual transmission, but the clutch pack and the automation of operation are very close to that of a normal automatic so to start let's look at the clutch pack what is a clutch simply a clutch is a way to connect or disconnect a rotating shaft so that the opposite shaft cannot turn or rotate when the two are joined together in this simple way Representation of a dry clutch that is typical in a manual transmission as the plates come together, the rotation From the engine is transferred to the transmission shaft and therefore starts to rotate, the PDK uses a different type of clutch.

These are a multi-disc wet clutch. means that there are alternating discs that are splined or locked both on the outside, in this case connected to the engine, and on the inside, which is connected to the drive shaft, in this case here the engine can rotate freely without the drive shaft. transmission spin, but if pressure is applied so that the discs slide sideways and hold tightly against each other, then the motor and drive shaft are now locked and the drive shaft rotates. If they are completely locked, then the engine and driveshaft rotate at the same speed but the pressure applied to the clutch discs can be regulated so that slip is created between the discs.

An example of this is when you start moving from a stop and need a gradual grip of the clutch for smooth acceleration. Clutch slip is deliberately used at different times during transmission. operation If you have ever driven a pdk equipped car, when you release the brake and don't put your foot on the accelerator, the car will accelerate smoothly to about 5 kmph and stay that way very similar to how a standard automatic behaves when you release the brake in this In this situation, the clutch slips constantly as the engine RPM in first gear is too high for this speed, so the clutch slips so that the car does not move at too high a speed while using brake fluid. transmission to engage the clutch.

It is used to cool and lubricate a separate stream of lubricant and cooling fluid that starts at the hub and flows through the package to the outside. This provides much better wear resistance when there is slippage between the discs and also cools the entire pack as there are grooves in the disc which allows fluid to flow through the clutch pack even when they are joined together in a dual clutch transmission. two of these clutches which are nested in a single package each of these clutches is connected to one of the two drive shafts the long drive shaft is located inside the short shaft the large clutch called clutch one is connected to the long inner shaft and the small clutch, clutch two is connected to the short outer shaft.

Please note that the arrangement of the clutches in the package is different than what I have depicted. I've done this here for simplicity so you can easily see the two clutches, so now let's take a look at the clutch pack and components and how it all fits together. First, you will notice that the transmission bell has opened. Pdks don't normally look like this, it's the result of the accident on the track and that's how I became the recipient of the donation. This is the clutch pack. Excuse how rusty you are. It had been sitting in the previous owner's shed for a while.

The front part is the cover that is pressed onto the clutch with a bearing so that the cover remains stationary when the clutch rotates. This knob on the front, which is part of the clutch pack, is locked to the flywheel, which is the output of the engine, so whenever the engine is spinning, the cover remains stationary, but this whole outside part of the clutch will rotate with the engine when the clutch pack is removed. You can see both input shafts rotating independently of each other by looking at the clutch pack when it is rotated. You can see the passages where the fluid goes through to activate each clutch when I turn it over and then I remove the front face that they cut off, we can see what is inside this first piece is the internal part of the large clutch that fits inside . input shaft without this you can see the same part but for the smaller clutch that is installed on the outer input shaft without this you can now see the two clutch packs.

The first thing you should notice is how for both clutch packs the steel discs are locked into the outer casing of the clutch pack and the friction discs would be locked into the internal parts of the clutch. I have removed each of the packages. The clutch can be removed. One can simply flip it over and the package falls out and you can see the alternating steel. and the friction discs also note the grooves in the friction disc which are there to allow fluid flow through the discs. Clutch pack two can be removed after removing this spring ring.

This spring ring is what the clutch pack compresses against when activated and is very typical of a standard automatic clutch pack design clutch does not have a retaining ring as it is compressed against the front face of the clutch which It has been cut here when the packs are removed, you can see the actuation pistons that are used to activate each clutch, each piston is not a circle, but an annular shape with a large O-ring on the inner and outer surfaces of the roof, where it slides up and down. Each also has a large spring that pushes the piston down when the pressure is released, just the spring for the clutch. is visible here here I am applying compressed air to each of the fluid ports on the other side to simulate clutch activation clutch one and now clutch two the clutch itself is installed in the transmission on this piece called the intermediate plate which is normally Bolted to the transmission behind the clutch pack it has many machined channels that carry the fluid to where it is needed from the valve body.

I will cover the valve body with fluid flow later. You can see here the channels where the fluid reaches each clutch on the other side once the clutch pack is installed, so if I place the intermediate plate in the housing, for this I have removed the entire clutch disc to be able to rotate each piece freely. Now I can fit the clutch pack housing, which is the part that fits the rear of the engine and will always be spinning if the engine notices that none of the input shafts will spin. Now I can attach the inner part of clutch 2 that locks onto input shaft 2.

When I rotate this piece, it is now turning shaft two. Now I can fit the inner part of the clutch that locks onto axis one. I can also rotate it independently of the outside and the engine, but if I simulate locking the clutch plates, you can now see how the rotation of the engine now rotates the transmission input shaft. Now let's talk about gears and we'll start with the basics. The gears in the pdk are identical to those found in a manual gearbox. You have a gear that is on the input shaft and another that is on the main shaft, which is the output shaft.

Of these gears, the larger of the two will always have a bearing inside so that it can rotate relative to the shaft. This is called loose gear. The opposing gear will be permanently attached to the shaft. This is called fixed gear. In this example, you can see that the input shaft on the left has the fixed gear, so every time the input shaft is rotated, this gear will rotate when the input shaft is rotated, the loose gear on the right. It will also rotate, but the main shaft will not because the gear can rotate. freely due to the bearing to make the main shaft rotate, the loose gear must be locked to the main shaft.

I will explain how this is done in a moment so that each ratio in the transmission is a pair of gears, one loose and one fixed, depending on the ratio the large gear could be on the input shaft so this gear lock to the axle must occur here, but the mechanism for doing this is the same regardless of the axle, while I said that each gear ratio is a pair in reverse is different, it has three. The two gears on the input and main shafts do not mesh and there is a third gear called an idler gear that is installed between them so that the rotation of the main shaft is reversed with respect to all other feed gears, the relationship between the input shaft and the main shaft is determined. entrance and the main one. by the number of teeth in each, for example in first gear, the input side has 11 teeth and the output side 43 teeth, which gives a ratio of 3.99, this means that the input shaft will rotate 3 .99 times to make the main shaft rotate once if it has ever done so.

I looked at the gear ratios and wondered why they have these strange numbers. It's because of a concept called hunting tooth relationships. I won't go into too much detail, but I already said that it is not desirable that the number of teeth in each gear be such that the same tooth regularly. meshes with a corresponding tooth on the other gear, this will cause the gear teeth to wear poorly and unevenly and cause additional vibration and noise, so the numbers of teeth on each are chosen carefully, often using prime numbers to avoid this problem, hence we get these strange proportions.

Numbers, let's talk about how a loose gear locks to the shaft. I will first explain it using graphics and then go to the broadcast. Next to each loose gear is a hub that is tightly locked to the shaft on the outside of it. It is a sliding sleeve that has serrations that allow it to slide sideways but will continue to rotate with the hub in the loose gear. There are extra small teeth around the outside called dog teeth to lock the gear to the shaft. The sleeve moves to the sides and locks. into the dog teeth with the result that the gear is now locked to the shaft.

The problem with this is that the loose gear rarely has the same rotational speed as the shaft, so without ensuring that the gear and shaft have the same speed before coupling. dog teeth will wear or break very quickly. This is where the synchronizer comes in, shown in the orange ring shown here, which sits between the gear and the hub and is used to ensure that the slider and gear have exactly the same speed before engagement. So how does it work? The inner part of the synchronizer is conical in shape and is designed to fit into the conical partcorresponding Loose Gear.

This inner surface has a friction material. The synchronizer also has teeth similar to dog teeth. In the gear there is also this piece called a strut. This is a piece that has a small metal ball and a spring and a small notch in the slider that maintains the position of the ball, so that when the slider moves sideways, the metal ball takes the strut which in turn pushes the synchronizer to the sides when the friction material of the synchronizer comes into contact with the corresponding surface of the gear, this changes the speed of the gear to match due to the slight clearance of the synchronizer ring, its teeth will be misalign the slider until they are both at exactly the same speed at this point the slider can move completely sideways and slide over the synchronizer teeth and engage the gear dog teeth when this happens the strut ball moves down out of the notch allowing this strut to return to its original position, although this may seem a little confusing when I go to the transmission and shift, this should be clearer also in the largest gear selected, being first, second, third and reverse, triple synchronizers are used for These are three synchronizer rings, all nested together instead of one.

It's like the clutches we saw previously, where there are three discs instead of one. The reason is that these gears are much larger and heavier than the others, so the rotational inertia of the spin is loose. The gear is larger when the synchronizer is used to change the gear speed. By selecting the basic principle of how it

works

, the movement of the slider, shift fork and shift is not changed. Rods are also used in the PDK, unlike a manual transmission, each shift rod has a magnet attached which is used to detect the position of the gear lever.

Finally, each slider can engage two possible gears, it will be located between the two and depending on the direction the slider moves, it will engage one or the other. Note that there are eight gears in total on the pdk, seven forward gears and one towards the rear, so there are four shift rods in total. Each of which can select two possible gears. Also note that when you shift gears in a manual transmission, this forward or reverse movement of the shift is exactly what you are doing when you move the shift lever in the pdk; however, this is done automatically using the transmission fluid and the valve body, which I will cover later, so let's look at the transmission here it is without the rear housing.

What to see here are the four shift paddles and the attached magnets used to detect shift positions. These two shift rods one and four are for the gears at the front of the transmission that can't. You can see that shift rod 3 is for first and third gear and shift rod two is for fifth and seventh. There are currently no gears selected and if I turn the input shaft that is connected to all of them, you will see the fixed gears that are locked. to the input shaft the first and third will rotate but the seventh and fifth do not rotate because they are loose gears with bearings observe the selector hub for the fifth and seventh turns because it is locked to the input shaft I will put the transmission on its end so that be easier to see and we'll get a closer look at the fifth gear right at the end.

I can remove the fixed gear on the main shaft by sliding it off. You can see the splines that lock it to the shaft. The gear on the input shaft. Now I can rotate freely on the bottom bearing. If I move the slider to engage the gear, you can now see that the gear is locked on the input shaft and therefore the input shaft rotates. You can also see the other fixed gears turning and the associated loose gears. but the output shaft does not rotate because I removed the associated fixed gear. If I now replace the gear on the main shaft and turn, 5th gear is fully engaged and the main shaft rotates.

Let's take a closer look at the operation of the loose gear and synchronizer. Note that the diagrams I used before had everything much more spaced apart for demonstration, the movement of the synchronizer is actually much less, maybe a millimeter, as you can see here the Loose Gear spins freely and if I remove it you can see the bearing below and the synchronizer. ring you can see the conical surface of the gear and also the corresponding synchronizing surface with its friction material. These are the two surfaces that grip each other to change the speed of the loose gear.

Here is a closer look at the strut with the ball out of where it should be and I adjusted it correctly by compressing the spring and pushing it into place with the slider out of position, you can see the detent that holds the metal ball and moves the strut when the slider is moved if I put everything back in place. in the center position and move the slider slightly you can see the strut moves with it because the ball is stuck in the notch and if I replace the synchronizer and simulate the initial part of the shift rod movement you can see that the synchronizer rises. synchronizer locking teeth and also this part that will be pushed by the strut with the synchronizer in place, you can see that the width of this part is slightly narrower than the space for the strut, so if I simulate this synchronizer ring being pulled From the gear that is spinning you can see that the synchronizer locking teeth are misaligned with the teeth of the slider, so the slider can't move any further only when the gear and slider have the same speed.

Does this allow the pressure of the slider to push the locking teeth back? slightly which would allow the slider to pass over it and if I now put the gear in and turn it you can again see the locking teeth moving sideways due to friction with the synchronizer which again is what is blocking the movement of the slider until the speeds are the same, to show a selected gear, I will select seventh and remove fifth so you can see it a little easier when I start to move the slider, you can see the strut move and with it push the synchronizer ring below when the gear is selected. is the same speed, then allow all the teeth to align and the slider moves to fully engage the dog teeth with the strut springing back to its original position.

Now let's see what makes a dual clutch transmission special, firstly let's consider a very simple transmission that is not a DCT and only two gears, first and second, to select first gear you needed to press the clutch pedal to disengage it , select the gear and then reengage the clutch to shift gears to Second, you must disengage the clutch, select the gear then engage the clutch again, although this is a completely fun process for the enthusiast, it takes time to shift and requires some level of skill and coordination if we now consider the dual clutch transmission and a very simple one in which we have these two gears, first and second. but on different input shafts and therefore different clutches, if the first is selected, the second can also be selected, clutch one will be activated initially to start moving the car and when the shift to second gear is commanded , this is simply a case of changing the clutch that is engaged.

In the fraction of a second it takes to shift the clutch, the engine RPM will change rapidly during the shift, so that the engine and the new required input shaft speed are close before the new clutch is engaged, the speed shift, which is simply a case of how The speed with which one clutch disengages and the other engages is largely determined by the way the car is driven. If you are my wife and you are driving around town, this shift is relatively slow and smooth, but if you select the sport driving mode and drive aggressively, the shifts are super fast and sharp and sometimes both clutches will engage slightly during the change.

In the end you have an automatic transmission with very direct transmission characteristics like a manual transmission, but with the added benefit of very quick and responsive shifts. If you now put third gear in place, the shift rod can be moved to select this gear in preparation for the transmission control unit or TCU to command third gear. This process of anticipating the next gear is called pre-election and it is the TCU that predicts the next gear. will be used in this case when second gear is engaged, the next gear could be first or third and usually the TCU predicts it based on whether you are accelerating or decelerating, sometimes if you have no ideas when neither the TCU accelerates nor decelerates.

We do not preselect the gear and will wait for the driver to show his intentions before doing so, so if we increase the transmission, add fourth fifth, sixth, seventh and finally reverse gear, the reverse idle gear is shown in pink here, everything is spacing here. For clarity, but in the transmission it is much tighter so you can see that the three even gears in total are on the shaft and the clutch two in the front of the transmission and all the odd gears in reverse, five gears in total they are on the axle and clutch one at the rear while it may seem strange to have five gears in one clutch and three in the other in reverse and they are put into clutch one first as the larger clutch is preferable for starting from a standstill and move the shift rods there.

There is a cylinder and piston at the front of each transmission. Fluid can be sent to either side of each piston so that the shift rod can move forward or backward depending on the gear being engaged. There's also a clever gear lock system in the transmission that mechanically prohibits some gears from being selected when others are. There are notches in the shift rods and a metal pin that sits between them to prevent the other shift rod from moving, so if the lower shift rod is moov to select a gear you can see how now the pin prevents the other shift rod from being able to do so if first or third is selected, it is impossible to select fifth or seventh if second or reverse is selected, it is impossible to select fourth or sixth and if reverse is selected, it is impossible to select any forward gear here are these locking pins on the transmission between shift rods 1 and four now between shift rods 2 and three and the pins that lock the reverse gear of all the others are these two and also the one below here here I am selecting reverse and you can see the top two pins move to lock another selection for each of these shift rods.

There is also a spring-loaded pin that maintains the center position if no gear is selected if the transmission was for a front-engine, rear-wheel drive car. the main axle would be the output to the wheels, this is the case for the four-wheel drive versions for the 9/11 as it would go to the front wheels, but in all Porsche sports car applications that have a mid-engine or rear, the drive shafts come out of the side of the transmission to achieve this, there is another fixed gear attached to the main shaft which spins what is called the pinion shaft, this pinion shaft then spins the differential which in turn spins turning the axle shafts which then turn the wheels in some Transmissions, this relationship between the main shaft and the pinion shaft can be changed to obtain a change in the final ratio in all years.

The base 2.7 L 981 transmission is an example of this, the ratio here is lower which in turn lowers each gear in the transmission I'm guessing this is done so that this low horsepower engine will provide better acceleration at low speeds. speeds at the expense of the maximum speed and finally on the pinion shaft is the parking wheel, this is a wheel with very large notches that is used to lock the pinion shaft and therefore does not allow the car move when Park is selected. A cable from the shift lever in the cabin connects to another lever on the side of the transmission which in turn pushes a post up inside the Park wheel when Park is selected and down. this when you select any gear other than Park so let's look at this in the transmission first let's look at the pinion shaft here is the fixed gear on the shaft you can't see the opposite gear on the main shaft as it's hidden back here if I turn the output shaft, you can see now that the pinion turns and also here is the parking gear with the big notches.

I have not installed it as it must be installed when the gear set is installed in themain casing when we look. On the rear housing you can see the parking lock mechanism, which is the same for almost any automatic transmission. Here the Sha sticks out the side of the transmission and is connected by a cable to the shift lever in the cabin. I'll put Park. The wheel where it would be located when installed will spin freely if Park is not selected, but if I pretend to select Park, this piece is pushed forward to lift the post and engage the parking wheel if the post does not line up exactly. this spring mechanism back here that then allows the post to sit lower until the wheel turns so the notches line up and then it locks into place.

This is exactly what happens when you select Park and the car moves slightly and then locks in Park here. You can see many of the transmission parts installed, but what to notice are the axle shafts that come from the differential that lives here. The half shafts can be easily removed and then the differential can be seen under the cover on the side when the cover is removed the differential falls off and then we can easily see the end of the pinion shaft, the bevel gear that turns the differential. Now I'll put the reverse idler gear on, but before I do that, here are the reverse gears as they look like this. the gears are very close to each other, they don't actually touch if I put the idler gear on and then turn the input shaft.

Now you can see how this causes the reverse gear on the main shaft to rotate in the opposite direction to all the others. Also notice that each gear is turning. I have engaged 5th gear in the rear but what it shows is that every time the car is driven all the gears in the transmission turn even though only a couple of gears are fully engaged with a clutch engaged in the front. From the transmission there will be another preselected gear that will have all of these gears driven by the mainshaft, so there is always a crazy frenzy of gears spinning inside the transmission, especially at high engine RPM and high speed at the front of the transmission .

I'll remove the intermediate plate and now you can see the four pistons and shift cylinders. I'll remove the piston and you can see the two seals that allow pressure to be applied from either side when the piston was installed, the fluid pressure on this side of the piston came through channels in the intermediate plate that we removed earlier to bring fluid to the further side. away from the piston, it comes from channels like this that then feed into the back of the cylinder here and if I put all the Cylinders and pistons when the gear set is removed from the front housing, you can see how the pistons screw into the end of the shift rod and then they fit inside the cylinder which concludes part one, the second part will cover the lubrication, the electrical cooling system and the valve body, if you are looking for more detailed information on the transmission go to my channel and there a playlist with many more videos containing much more information thanks for watching