A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term transmission refers simply to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device. J. J. Uicker; G. R. Pennock; J. E. Shigley (2003). Theory of Machines and Mechanisms (3rd ed.). New York: Oxford University Press. ISBN 9780195155983. For vehicles in particular, transmissions serve the purpose of transferring the engine torque to the wheels in an optimal fashion. The really high rotating frequency of the engine is not optimal and can damage the engine itself when the vehicle is slowing down, starting up or moving at a slow speed. To overcome this challenge, a system of gears and gear trains are used to transfer the torque to the wheels of the vehicle.
There are largely two fundamental types of transmissions used in trucks, i. Unsynchronized and ii. Synchronized An unsynchronized transmission does not use synchronizing mechanisms. Unsynchronized transmissions are often found in heavy-duty vehicle for agricultural and commercial purposes. These heavy-duty vehicles are often tasked with extreme working conditions, hauling heavy loads for almost the entire lifespan of the vehicle. Unsynchronized transmissions, colloquially known as manual transmissions, require a good understanding of the engine torque, frequency, engine power, gear change rates, gear change range, etc. Certified and professional personnel are required to operate such vehicles because of the serious safety hazards they pose. Nonetheless, such vehicles can tow up to and sometimes even more than 40 tons at job sites. Trained operators understand the engineering of these transmission and shift gears in a known coordination of timing. Sometimes a double-clutch technique is also used and taught and driver’s schools. A double clutch technique employs floating the transmission in and out of gear, bringing the engine exactly to the rpm needed before switching over to the higher gear. These gear change techniques are performed by only highly skilled operator who have an extensive knowledge of the gear transmission and engine rpm. With payloads of cargo ranging in commercial freight of 80,000 lbs (40 tons (short) or 36.3 tonnes) or more, some heavy haulers have over 24 ″gears″ (i.e., combinations of gear ratios) that an operator will shift through before reaching a top cruising speed of 70 mph (113 km/h). Many low-low (creeper) gears are used in farm equipment to plow, till, or harvest. An inexperienced operator could suddenly find a piece of heavy equipment stuck in the wrong gear under full power, or even worse unable to shift a runaway vehicle from neutral into a gear for braking effect when headed down a steep slope, unless he or she possessed the synchronizing skill and understood torque issues in nonsynchronous transmissions. Many mountain roads require heavy equipment operators to remain in gear and not shift while operating down a steep grade. This type of transmission is popular for large trucks, machinery and race cars. It has the benefits of being a simpler design which ultimately increases reliability and costs less for repairs over the long term. For large trucks, there is an added benefit of a significant reduction in weight, which allows greater cargo to be carried. Synchronized transmissions Synchronized transmissions, on the other hand, are different in that the gears are always meshed together in the gear box, requiring less effort to shift gears. Transmission gears are always in mesh and rotating, but gears on one shaft can freely rotate or be locked to the shaft. The locking mechanism for a gear consists of a collar (or dog collar) on the shaft which is able to slide sideways so that teeth (or dogs) on its inner surface bridge two circular rings with teeth on their outer circumference: one attached to the gear, one to the shaft hub. When the rings are bridged by the collar, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission. The gearshift lever manipulates the collars using a set of linkages, so arranged so that one collar may be permitted to lock only one gear at any one time; when “shifting gears”, the locking collar from one gear is disengaged before that of another is engaged – Wikipedia, Synchronized transmissions
How do truck transmissions work ? Large and heavy trucks use up to 3 forms of transmissions. These are known as range, splitter and range splitter. Range Transmission Range transmission is very similar to the ones used in smaller trucks. The only difference is that they have a high-low gear split whose purpose is to allow reuse of the same gear shifting position for both low and high gears. The Splitter Transmission The splitter transmission also features a high-low division mechanism. But instead of featuring a high and low section, the gear features something called a ”split-into-2” to make sure that each position of the gear is utilized for two gears, high or low. Range Splitter Finally, the range splitter is a perfect combination of the two gears above. It allows for greater flexibility, selection and range of movements compared to the above setups. To increase speed When a bigger and smaller gear are connected together and rotating, the smaller one will have to rotate faster to keep up with the speed of the bigger one. In such an arrangement, the second wheel will turn much faster than the first one without using additional force. So it’s easy to see how speed is increased and decreased accordingly. Increasing force In the event that you pair up two wheels, with the second wheel having more teeth than the first one, i.e. bigger than the first one, it will turn slower than the first wheel, though with more force. The bigger wheel will definitely have more force in a gearbox. Going the opposite direction When two wheels make contact, the second wheel will always go the opposite direction in relation to the first one. In fact, some vehicles will use specialized shaped gears to make the power of machines change angles. Whenever one wheel moves in any direction, the other one will automatically turn the opposite direction. However, with gears, they don’t have smooth edges; they must be teethed to prevent them from slipping against each other.
A little about me and my business My name is Brandon Mendell. Owner, leader and diesel engine enthusiast at Brandell Diesel Inc. I take great pride in running, fixing and appreciating diesel engines. As a boy growing up on the farmlands on Southern Alberta with my father I developed a love for these machines and have carried on, on the path for the past 20+ years. We proudly serve companies, fleets and individual owners of diesel engine vehicles and personally look to it that we do whatever it takes of save our customers any downtime. We are known all across the province of Alberta for our fast turn around times on diesel engine vehicle repairs and the rescue service we provide on the roads with our trucks. Don’t hesitate to call me at 403 271 0101 for repairs or consultation on your diesel engine vehicles. I look forward to hearing from you my friend !!