Automotive Q&A

Learn about your Transmission

What is a manual transmission service?

Whether you have front- or rear-wheel drive, transmissions are required to transmit the necessary power and torque from your engine to your vehicle’s drive wheels, Transmissions allow an engine to operate at a few speeds or gears, while your vehicle can travel at a large range of speeds. Each gear in a manual transmission has a maximum range of RPMs (revolutions per minute), referred to as a redline. Manual transmissions are very different than automatic transmissions. The most obvious differences include a manual transmission having both a clutch pedal and a gearshift or a stick shift, while automatic transmissions have neither. A manual transmission includes a clutch, gear selector fork, collars, and several gears and shafts. Compared to an automatic transmission, a manual transmission is very simple. There is one main shaft that supplies all of the power to the manual transmission. This initial shaft is powered and turned by the engine. The shaft travels through your vehicle’s clutch and is connected to a gear. A clutch is responsible for connecting or disconnecting the engine from the transmission. Since your engine is always running, your clutch must be engaged in order to stop your transmission from turning (this is why your clutch must be engaged when your vehicle is stopped and when you are shifting gears). Then, once your clutch is released, your engine is reconnected with the initial shaft and the transmission. When the engine is connected to the transmission (the clutch is released), the initial shaft’s gear is connected to another gear that powers the layshaft. The layshaft contains seven total gears that all turn as one. The first gear is connected to the initial gear and shaft mentioned above, and the six other gears are connected to gears corresponding to first through fifth gear and reverse. For the purpose of this service description, we will call these six other gears, which correspond to what gear your vehicle is in, shift gears. So far we know that the initial shaft and gear is connected to the layshaft, and then the layshaft’s gears are connected to the six shift gears.The six shift gears rotate around but are not connected to the transmission’s final shaft, which is connected to your vehicle’s drive wheels. What does connect the shift gears to the final shaft is one of three collars. These collars are directly connected to the final drive shaft and can move left or right to connect to a shift gear. Now, this is finally where your stick shift comes into play. The stick shift controls your transmission’s gear selector fork and tells the selector fork which collar to move and to which gear the collar will be attached. Each collar can connect to one of two shift gears: the first collar can connect to either the first or second shift gear, the second collar can connect to the third or fourth shift gear, and the third collar can connect to the fifth or reverse shift gear. Summing it all up, let’s say that you wanted to shift from third gear to fourth gear. First, you step on your clutch and move your stick shift from third to fourth gear. This will tell your transmission’s gear selector fork to move the second collar and connect it to the fourth shift gear. Then after you release your clutch, the engine will be reconnected to the transmission and the initial shaft will connect to, and turn, the layshaft. The layshaft will then continue to turn all of the shift gears, and since the collar is connected to the fourth shift gear, the fourth shift gear will turn the final drive shaft and power the drive wheels. However complicated it may seem, it is a very simple process. Now that we know how a manual transmission works, we can discuss what occurs during a manual transmissions service. In order to keep your manual transmission working as efficiently as possible, this necessary service is required. During this service, your transmission fluid will be drained and replaced.