That is why you need to reduce its speed by downshifting to a comfortable speed before applying the brakes. Otherwise, you will destroy the brake pads, clutch, and many other components in your truck. At one time, all heavy-duty trucks employed transmissions derived from tractors. But this was only sensible when heavy-hauler drivers had an agricultural background and had lots of practice operating manual transmission machinery. The transport industry has learned to accommodate folks from all walks of life, and this has had many surprising benefits.
Many people mistakenly assume that the transmission in heavy trucks is an enlarged version of those found in cars. Although their principle of operation is the same, big rig transmissions often lack the synchronizers that simplify shifting in cars. To use these transmissions, you need a great deal of practice.
Manual truck transmissions also have a separate inbuilt, pneumatic-controlled dual-speed transmission that controls the low and high range. Most of these transmissions will require the driver to start on the low range, shift through all transmission gears before engaging the high range. Others, however, require the driver to use the range control between the gear-shifts. Their shift pattern goes something like: first low gear, first high gear, second low gear, a second high gear, etc.
To easily understand how an automated manual works, imagine a robot seated in the passenger seat doing all the shifting for you.
They give you increased acceleration, increased ease of use, better fuel economy, and longer transmission life. The reason is that PGAs depend on several hydraulically controlled clutches for power transfer.
These clutches are prone to slippage and do not provide a positive engagement like a standard transmission. This is critical for trucks since they depend on engine back-pressure to descend safely on hilly surfaces. When hauling important cargo while trying to beat a deadline, the worst thing that can happen to you is your rig developing problems. Problems with your transmission can have some of the most costly ramifications.
The good news is that with a little insight and keenness, big rig drivers can recognize warning signs indicating transmission problems early. When troubleshooting your semi truck repair needs, keep these symptoms of semi-truck transmission problems in mind. If you hear noises such as grinding, screeching, buzzing, or clicking, you need to have your truck checked by a specialist. Usually, these sounds show that major components of the transmission system are failing, and these include the clutch release and the pilot bearing.
If these parts get damaged completely before you get your rig checked, you may incur additional damage and expenses. Some common signs of inconsistent shifting include slipping gears, inability to get into gear, revving between shifts, and taking too long to shift. Sticky shifting can result from various problems and may include problems with computer cables or sensors or faulty oxygen sensors. Their brakes and clutch are stiffer as well.
That is why these vehicles are more difficult to drive. For manual transmissions, each gear has a particular range and fuel distribution. The gear ratios differ with the engine type and the number of gears.
A normal sedan is started at the first gear, then allowed to gain a certain amount of speed before engaging the second gear. You are always advised not to drive in one gear for too long and not to drive in the low gears for too long.
For a sedan, starting in the second gear puts a lot of pressure on the clutch cable and plate and may also damage the pressure plates. Thus, to get optimal performance, you need to start a car in the first gear. However, this is not the case for trucks. Trucks have huge engines.
These engines produce massive acceleration and torque. Thus, truckers usually avoid starting the truck in the first gear to avoid losing control. If you start a truck in the first gear, it gains higher speeds quickly because the first gear has a higher fuel distribution. Other gear mechanics also contribute to the truck gaining higher speeds. It is, therefore, harder to control the truck in the first gear, and there is a higher possibility to lose control of the truck and cause it to spin.
A spinning truck is a great disaster because it can crash into anything or even topple over. Truckers are often advised to start the truck in the second gear to reduce the shoot-up effect and to make the take-off slower and more controllable. Thus, one reason for trucks having many gears is to compensate the gear ratios for not having to start from the first gear to gain stability.
The driver shifts from the second to the fifth gear as you would for a normal sedan then split up the gear into the high range. Then, shifts again from the sixth to the ninth gear. From the ninth gear, the driver splits up to overdrive for the top gear. There are lots of gears in between since all the main gears have a high and low range with different RPMs.
However, their power band is very narrow, and the difference in revolutions between the gears is often less than RPM. So, as the driver, you can split these gears as necessary.
As the driver practices and gains more experience driving semis, he will realize that the gear being used may not be the right one for where he wants the RPMs to be. Here, he will shift up or down as needed to match the RPMs to the sweet spot of the engine. This is another reason semi-trucks have so many gears; to select the right RPM depending on the speed of the truck. You learn how to do this right in truck driving school. There are times when you an unexpected halt in the traffic can cause you to slow your truck down rapidly and stop in the midst of heavy traffic.
It could be an accident or a police checkpoint. Either way, you need to stop. Home Blog Brochure Application Contact. How many gear does a trailer have?
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