In my second article titled, “How a Manual Transmission Works” I explained how most modern cars with manual transmissions work. Those cars come with synchromesh transmissions, and since they where covered in detail in that article. I will focus on other types of transmissions you may encounter, and are worth knowing about. Then give a brief over view of how to operate one, in the event you find your self driving one of those vehicles.
Sliding Mesh Transmission
This is an older style of transmission that isn’t used much these days. However they are commonly seen in cars built before the 1950s, so should you find your self driving one. You will at least not be surprised when the gears grind when shifting. The good news is you can minimize that by double clutching, and getting used to the gear spacing. Also don’t be alarmed if you hear a more pronounced whirring noise when driving. These transmissions are known to be noisier than more modern transmission designs.
As the name implies this transmission works by sliding the gear ratios together with the shifter fork. As opposed to being fixed in place as seen on modern synchromesh transmissions. Because you have to slide the gears in place, this requires the driver to have those speeds match perfectly. Otherwise the transmission will grind and not go in gear. Doing this too often can cause damage to the transmission, hence why modern transmissions use an easier to shift synchromesh design.
Dogbox
These types of transmissions are common on motorcycles and race cars. They are used in these applications, because they save weight and are more durable. This is because they don’t have synchronizer rings as seen in road going cars now days. Which also means you have to double clutch these transmissions, just like in a sliding mesh transmission. However more experienced drivers successfully shift these transmissions with out a clutch. Keep in mind it takes practice to master shifting gears with out the clutch.
These transmissions have constant mesh gears much like the synchromesh transmissions, but the big difference is how each gear is selected. Instead of using a synchronizer ring that spins and locks onto the chosen gear. These transmissions have sliding gears that are attached to the shifter fork, and they are called dog clutches hence the name “dogbox.” They have teeth that slide into the grooves of the chosen gear once the speed is properly matched.
Auxiliary Overdrive
These are non existent on modern vehicles, as over drive gears are built directly into transmissions now days. However back in the early days of freeways when cars where going faster all of a sudden. Many cars at the time didn’t come with an overdrive gear. Which is a gear ratio that allows the engine to spin slower than the output shaft of the transmission. Instead of developing a whole new transmission, motor companies would simply add a reduction planetary gearset outside the transmission.
To keep it simple a planetary gearset is a set of gears that orbit around a sun gear. When the sun gear is activated via mechanically or electro magnetically. It would reduce the speed of the output shaft of the transmission. Thus having the same benefits of an extra gear with out the complexity of a five or six speed manual. However now due to better technology, it is less cost prohibitive to manufacture transmissions with more gears.
Automated Manual
While technically not a manual some automatic transmissions operate more akin to a manual. Instead of the typical torque converter and planetary gearset design. They use a computer controlled clutch with constant mesh gears like you would see in a manual transmission. Sometimes they come with two clutches, and are called dual clutch transmissions. The benefit of automated transmissions is they shift super quick and allow for either manual or automatic gear selection. However these transmissions are known to be costly to repair, when compared to traditional manuals.
Tractor Trailers
These large vehicles probably have the most unique transmissions out of any vehicle on the road. Because of their heavy weight and low revving diesel engines. They tend to be seen with 10 to 18 speeds now days, older trucks had even more gear ratios. However much like older cars, trucks from the 50s till the 70s had two transmissions. The auxiliary however would usually be a full on transmission, much like the main transmission.
Now days the extra gear ratios are accessed via toggles on the gear shifter. Usually on a 10 speed, they come with one toggle which essentially accesses additional ratios. Transmissions with more gears will have an auxiliary over drive similar to what is seen on classic cars. However these are usually air operated instead of being electronically activated. Many modern trucks just like supercars also can be seen with automated manuals. However just like with cars they get mixed reviews from different drivers.
Conclusion
As you can see from this article there is many different manual transmissions that are used in various different applications. That range from weight or speed the vehicle will be operated at, or just simply the time period when the vehicle was manufactured. With this knowledge you can pretty much drive anything you want to now with some practice. I hope this article helped you gain some insight, and I appreciate you reading this far.