Before going further, it is a good idea to learn how a manual transmission works. This article is going to cover how modern synchromesh transmissions work. Which is the bulk of where most of you will be starting out on, but if you are curious. I wrote another article that covers the different types of transmissions seen in various different vehicles. Back to the topic on hand I will go through step by step the major components and what they do.
The Clutch and Pressure Plate Assembly
The Clutch is a plate made out of similar materials to a brake pad. That presses up to the back side of the flywheel. The flywheel is connected to the back side of the engine via the crankshaft. They are pressed together with a diaphragm spring inside the pressure plate. The clutch pedal controls a hydraulic mechanism, that separates the clutch from the flywheel. Sometimes it is done pneumatically (compressed air) or non assisted.
In the first article I mentioned how you don’t want to leave the car in gear with the clutch in. The reason why is because it causes the pressure plate assembly to be under tension. Which can cause the pressure plate assembly to wear out faster when used more often. To the point where your clutch won’t engage anymore until repaired. This helps make sure that you get the longest life possible out of your pressure plate.
Shift Linkage Assembly
The shifter in your car is connected to the transmission via the shift linkage. Usually the shift linkage is made up of a pair of metal rods. However some modern vehicles use a cable linkage instead. The shift linkage then connects up to the shifter forks. These basically connect or disconnect the gears inside the transmission to the rest of the drive line. I will explain more on how this works in the next section.
Synchromesh Assembly
This only applies to modern cars with constant mesh transmissions. Meaning a gear ratio is made up of two gears constantly meshed together, regardless if they are selected or not. These two gears are housed on two different shafts in the transmission. The input shaft connects to the clutch side of the transmission, while the out put shaft connects to the differential. Sometimes a transfer case if the vehicle is equipped with four wheel drive.
When selecting a gear, the appropriate shifter fork will move the chosen shifter collar. Typically two gears will share a collar, for example first and second share a collar. This collar slides over the synchronizer ring teeth, which locks in and pushes against the blocker ring. Which is connected to the set of gear ratios by either the input or output shaft. Depending on the design of the transmission. The synchronizer ring will also be slightly off plane from the blocker ring to allow the speeds to match up evenly.
Once the teeth on both the Synchronizer ring and blocker ring are matched you will have an effortless shift into that gear. Sometimes with worn transmissions, cars that where driven hard, or poorly designed can have damaged synchro rings. This means that the transmission will grind when trying to shift gears unless it is double clutched. This is a technique I will cover in a later article. If you remember in the first article I recommended against resting your hand on the shifter. That habit damages the teeth in the synchromesh assembly over time.
Putting it all Together.
While it may seem complex at first, understanding how a manual transmission works. Will help you as the driver better understand what is going on when you are driving. Which is important for knowing how to shift gears smoother, and avoiding un-necessary repair bills. Now that you have a better understanding for how a transmission operates. In the next article I will show techniques that race car drivers and truckers use for better shifts. I appreciate anyone who read this far, and see you on the next one!