I'm Jake O'Neal, creator of Animagraffs, and this is how a manual transmission and clutch works.
Manual transmissions are rare in new consumer cars, but millions of units still exist in older
cars, commercial, and racing applications. For this video we've chosen a front wheel
drive arrangement. Our transmission model
is a constant mesh type design, where gear sets are always in contact with each other.
Let's start with the clutch. The clutch assembly is securely attached
to the flywheel, which is bolted to the engine. It's always spinning if the car is running.
The components inside this assembly allow power flow to be disconnected
from the transmission input shaft. Note that the transmission input
shaft does not itself connect to the engine crankshaft or flywheel.
Connection to engine power is accomplished with a sliding friction disc sometimes
called a clutch plate, sandwiched between the flywheel surface and a movable pressure disc.
The clutch plate assembly is splined to the transmission input shaft,
but can slide back and forth. The pressure disc gradually squeezes everything
together as the driver releases the clutch pedal for a smooth connection to engine power.
To further ensure smooth power delivery, the clutch plate has a built in damping system.
The friction disc floats on the transmission input shaft.
Power flows from the disc, through damping springs which push against a rotating top plate whose
center is splined to the transmission input shaft. The springs continuously absorb vibrations
or other potentially harmful anomalies in the flow of power.
Now let's look at how the pressure plate moves.
The pressure plate is connected to a special diaphragm spring.
This strong spring is what naturally presses the pressure plate to the flywheel.
The outer cover has hooks that hold the diaphragm spring securely in place, and act as a fulcrum.
There are also supporting leaf springs attached to the pressure plate and cover.
The clutch fork sits at the center of the diaphragm spring.
As the clutch fork pivots, it presses against a release or throwout bearing,
depressing the diaphragm spring's inner prongs which in turn lifts its outer edge,
and the connected pressure plate. Let's see that movement a few more times.
The clutch fork acts as a lever, with a fulcrum point on the transmission case interior surface.
It's driven by a hydraulic actuator
whose lines lead back to the clutch pedal with its own hydraulic actuator and fluid reservoir.
The gears
Each speed has a gear set so that input speed can be different from output speed.
The speed gears in this constant mesh transmission are always linked.
They have diagonal or helical cut teeth for quieter operation.
Notice the reverse gear set with its straight teeth – this transmission will make a familiar
gear whining sound when in reverse. Engine power flows through the main shaft
to the countershaft, to the differential assembly, and out through front axles.
Synchronizing gears To make gear shifting possible,
one gear in each set floats freely on its shaft, riding on a roller bearing.
the other gear in each set is either connected with splines
or directly machined into its respective shaft.
For power output, the floating gear in a set must become securely connected to its shaft,
through the synchronization process. Between each gear set, there's a
synchronizer hub that's splined to and rotates with the shaft.
A sliding shift sleeve is also driven by this hub,
which can be moved back and forth by a selector fork.
Forks are connected to sliding rods that are held by the external casing.
During gear selection, the fork moves the sleeve towards the desired gear.
A blocker ring sits between the sleeve and the gear. The blocker ring's job is to get
everything spinning at the same speed and lined up for a synchronization attempt,
or block further movement if synchronization isn't possible for whatever reason.
The hub has slots for three synchronizer keys that spin the blocker ring,
but allow enough play so the blocker ring can adjust on the fly as the sleeve teeth approach.
The shift sleeve's internal teeth are shaped to push against keys, which in turn
press the blocker ring against the gear. The ring's inside surface is conical and
has ridges to engage the cone shaped gear surface like a miniature clutch.
Gradually, the gear begins to spin with the blocker ring.
The keys are spring loaded. Once enough pressing force builds,
the keys are no longer needed, and move down and out of the way
allowing the sleeve to progress into its final synchronized position with gear locking teeth.
This process enables fast gear selection between rotating components while keeping main gear teeth
safe from the change procedure. Locking teeth on the sleeve and
gear are slightly angled in some designs, encouraging a more secure connection.
Now, power flows through the splined hub and sleeve
through the gear set, and out of the transmission. To switch gears, the clutch is pressed in,
pressure is relieved and the sleeve can slide into synchronization with an adjacent floating gear.
Since each sleeve can only slide between adjacent gears,
for this six speed transmission there are three selector forks and rods.
The first and second floating gears operate from the output shaft,
but this doesn't fundamentally change functionality in any way.
Forks and rods only move back and forth,
as directed by the shift change assembly.
This component can swing side to side to select a specific rod and fork,
and once selected, a metal tab pushes the fork one way or the other.
Let's trace this component's movement from the shift lever itself.
The shift lever rides on a ball that allows movement on two axes.
Each movement axis is separated into its own cable.
These work something like bicycle brake cables to translate stick movement to the transmission.
At the other end, cables are attached to a rod that protrudes out of the transmission case.
This rod can move up and down, or rotate based on distinct cable input.
A specially designed piece at the end of this rod moves connected components to swing side to side,
or slide the metal tab back and forth.
Reverse gear The reverse
gear has its own rod and selector fork. The transmission must come to a complete
stop to shift into reverse as there are no synchronization components.
Adding the third idler gear to the system reverses final output.
Neutral When in the neutral position with no gear selected
and the clutch engaged, meaning the clutch pedal is not pressed in,
the transmission input shaft spins, but since no gear is synchronized,
no power flows out of the transmission.
Oil Oils rests at the
bottom of the case and is splashed up onto gears for lubrication. There's no oil pump or filter.