How Does An 4l60e Automatic Transmission Work Animation

In Part 2 of this serial we will be diving deeper into the workings of one of the automated transmissions that we introduced in Office 1: the 4L60. Now that nosotros know the history of how these units came to exist, allow's look closer at what makes them work and the improvements that were made over time to make them piece of work ameliorate.

We will outset by discussing the get-go true automatic manual: the hydraulic planetary automated manual. This type of automatic utilizes several planetary gear sets, bands, clutches and a hydraulic system to accomplish the different gears. For this instance we volition use the well-known GM 4L60 (also known equally the 700-R4 — the OEM changed the unit name in 1989). This manual had seven positions on the gear selector: P, R, Northward, D, iii, ii, 1. These selections were:

• Park
• Reverse
• Neutral
• Drive
• 3 or Manual Third
• 2 or Transmission Second
• 1 or Manual Kickoff

The Torque Converter

Earlier we dive into the power menstruum in each gear, it'southward important to understand that the power must be transferred from the engine to the manual. That is where the torque converter (Figure 1) comes into play. You can encounter a detailed diagram of every component in a 4L60 298mm torque converter here.

Figure one –Assembled 4L60 Torque Converter

The clutch pedal on standards allows the engine to be momentarily disconnected from the manual to allow the vehicle to travel forward in several gears, travel in Reverse and placed in Park. In the early days of automatics this is where the fluid coupling came into play. A fluid coupling is an oil-filled housing that includes ii turbine halves. The cover assembly is attached to the flywheel and spins at the same RPM as the engine. The turbine assembly is splined to the encompass, which propels the transmission fluid through the angled fins on the turbine towards the other turbine — the pump — which is splined to the input shaft (Figure ii).

Effigy 2 – 4L60 Torque Converter Turbine Components

An age-onetime comparison to bear witness how this process works is to set up two desk fans facing each other and just turn i on. If they are close enough to each other, the air menses from the powered fan volition propel the other fan to spin. Much like there isn't a mechanical connection between the fans, there isn't actually any mechanical link betwixt the engine and transmission. Fluid couplings were phased out when torque converters were invented.

The divergence between a fluid coupler and a torque converter is that a torque converter contains a stator inside the housing. The stator is a cylindrical, turbine-like slice that is installed between the turbine assembly and the converter pump assembly. Its chore is to multiply torque by adding another redirection to the fluid path. The fluid now travels from the turbine associates to the stator associates, which redirects the oil and changes its direction of rotation to the same as the pump. This redirection increases the force of the oil that is driving the turbine therefore multiplying torque.

Gear Application

Afterwards the power is transferred from the engine through the torque converter, it is transferred by the turbine shaft that is pressed into the input housing. The input housing contains the Forwards clutch housing, piston, clutch plates, clutch outer race, roller assembly, clutch cam and finally the input sun gear. This brings united states of america to our first planetary prepare: the input planetary.
Planetary gears are named appropriately as they resemble a planetary system. They tin be used to increase or subtract the twisting force or torque from the engine. The planetary consists of a eye gear chosen a dominicus gear, surrounded by pinion gears, which are surrounded past an internal gear. For example, in GM's 4L60, in that location are two planetaries: the input (or front) and the reaction (or rear) carrier (Figure iii).

Figure 3 – 4L60 Input & Reaction Carrier Planetaries

Transmissions from other manufacturers will have different components and different methods of applying each gear, but the full general thought is still the same: use the planetary gear ready to provide the right gear according to load and speed. Allow'south take a look at the power menstruation with the 4L60 (700-R4).

1st Gear

First Gear requires more torque to become the vehicle moving from a standstill. This is accomplished by a process chosen reduction. In 1st Gear when Drive range is selected, the Forward clutches are applied holding the one-way Low and Contrary clutch, which prevents counterclockwise rotation of the reaction carrier because they are splined together. The reaction carrier is splined to the internal gear. Power is practical through the sun gear in a clockwise direction.

This makes the pinion gears of the input carrier orbit effectually the sun gear in a clockwise direction while individually rotating counter clockwise. Since the internal gear is restrained from rotating counterclockwise, the input carrier is forced to drive the output shaft which information technology is splined to. This results in a three.06:1 torque multiplication and speed reduction. In other words, the input shaft volition turn iii.06 times for every ane rotation of the output shaft. Combine this ratio with the maximum converter torque multiplication of two.0:one and yous have a 6.12:1 overall ratio.

2nd Gear

When shifting into 2d Gear, less torque and more speed is needed than 1st Gear. The Forward clutches are still applied, merely the input internal gear and Low and Reverse clutch are released. The Reverse input pulsate is held by the 2-4 band, which is a round band of metal with a friction surface bonded to it. Since the Reverse input pulsate is tanged to the lord's day vanquish, which is splined to the reaction sun gear, all three components will now be locked together. The input dominicus gear then drives the input carrier, output shaft and reaction internal gear. This forces the input carrier to transfer ability to the reaction internal gear through the output shaft. Second gear ratio ends up being 1.44:ane considering of the second reduction the reaction planetary provided.

Damage to the band, input/output shafts, sprag, etc. tin can exist lessened by properly cushioning the large ratio alter on the 1-2 shift. Reducing the ratio change volition improve overall launch in powerful applications, plus reduce stress on ring and clutches on the shift past converting 1st Gear from 3.06 to 2.84. Sonnax input carrier kit 77284-K is a unique gear set that does exactly this. Figure 4 shows the OE torque multiplication factors and ratio changes with an OE reaction carrier vs. the Sonnax carrier. Learn more virtually cushioning the 1-2 shift ratio change and the benefits of the Sonnax ii.84 gear fix in this article.

Figure iv – OE vs. Sonnax 4L60 Gear Ratios

3rd Gear

In Third Gear the Forward clutches remain applied, the 2-four ring is released and the three-iv clutches are applied. Power then flows through the input housing, forward clutches, input sprag and iii-4 clutches to the input sun gear. The input planetary carrier then drives the output shaft at one:1 ratio, or direct drive as it is known. Equally the speed increases, less torque is required, hence the need for unlike ratios.

4th Gear/Overdrive

Fourth Gear, or Overdrive as it is known, is unique in that it is the but overdriven gear. By applying the ii-4 ring, the Reverse input housing, input internal gear and reaction lord's day shell are held similar to 2d Gear. The departure between 2nd and fourth Gear is that in 4th the three-4 clutches are practical, which drives the carrier, which in plough drives the internal gear driving the output shaft at a ratio of .seventy:i. Overdrive still maintains vehicle speed, but improves fuel economic system past lowering the RPM of the engine.

• Selecting 1, or Manual Depression, provides maximum engine braking for situations such as descending a very steep loma. Transmission Depression can only exist selected if the vehicle is traveling less than 30 mph. In this position the Low and Contrary, Forwards and overrun clutches are applied and keep the transmission in 1st Gear.
• Selecting 2, or Transmission Second, allows the vehicle to get-go out in 1st Gear and make a 1st to 2d shift, but information technology is prevented from making a second to third shift. This selection mimics 2nd Gear in Drive range, simply the overrun clutch is applied to use the engine as a braking force.
• Selecting iii, or Manual 3rd, allows shifts from 1st to second and 2nd to 3rd, but is prevented from shifting to 4th Gear. As with the other manual selections, the overrun clutch is applied to utilize engine braking.

Reverse

Placing the transmission in Reverse activates the Reverse input clutches inside the Reverse input housing, which is tanged to the input housing. The reaction carrier is prevented from rotating clockwise by the Depression and Reverse clutches. The power at present travels from the converter through the input housing, to the Reverse input housing, to the reaction sun shell, to the reaction sun gear. Since the carrier is being held, the sun gear volition drive the reaction carrier pinons counterclockwise on their pins, which drives the reaction internal gear and output shaft counterclockwise at a ratio of 2.30:ane.

Shift Timing

Shift timing in early planetary transmissions is controlled strictly by hydraulic pressure that is supplied past a mechanical governor (Figure 5) that is driven by the output shaft.

Figure 5 – 4L60 Governor

The governor is supplied with a constant force per unit area from the oil pump. When the governor spins at dull speeds, centrifugal force acts on the larger and heavier primary weights beginning, pushing them outward, which moves the internal valve inside the governor endmost the exhaust port and increases the governor pressure. In one case the vehicle reaches a speed that forces the primary weights all the way out, they get unable to affect shift timing, which is when the smaller secondary weights come up into play. Because of their smaller weight, they are less affected by centrifugal force and provide the smaller adjustments at higher speeds.

Modern transmissions rely on electronic speed sensors and the vehicle'south throttle position sensor to provide the engine load data to the transmission control module (TCM).

Shift Utilise

While the governor controls the timing of the shifts, the hydraulic system is responsible for applying the clutches and bands. The heart of the hydraulic system is the pump, which is keyed to the converter pump hub and turns when the engine is running. The pump in a 4L60 (700-R4) is a rotor-and-vein-style and provides the necessary line force per unit area to the hydraulic organisation to utilize the bands and clutches.
The previously mentioned gear selector that allows the driver to select the desired range is connected to the transmission valve inside the valve trunk. The transmission valve directs the fluid path from the pump to the valves of the valve body. The valve torso is a circuitous associates of interconnected fluid paths, precision valves, checkballs and orifices (Effigy 6).

Figure 6 - 4L60 Valve Body & Pump

In older units, the valve body would utilize a valve for each specific gear change, called a shift valve. Each shift valve when stroked in the correct direction completes the fluid path necessary to activate the clutch pack(south) and/or band to attain the appropriate gear. In modern transmissions such as the successor to the 4L60 — the 4L60-E (Effigy vii) — gear changes are achieved electronically, instead of hydraulically, past using solenoids.

Effigy vii – 4L60-E Valve Trunk with Solenoids

A solenoid (Figure 8) is an electromagnetic valve that can be opened or airtight by applying voltage across the solenoid whorl past the transmission control module.

Effigy viii – 4L60-E Solenoid

The actual application of the clutch pack or band is achieved past using pistons and servos. These are devices that convert hydraulic pressure into mechanical force to provide the clamping force necessary to hold the ring or clutches without slippage. Stock and aftermarket servos come in different sizes to deliver dissimilar degrees of holding power. Larn more nigh 4L60-E servo options in this tech article.

New Fuel Standards Force Changes

While the main principles of the hydraulic planetary manual have remained mostly unchanged since transmissions like the 4L60 (700-R4), improvements had to exist made to increase fuel efficiency to meet the demands of tightening emissions. Equally covered in The Development of Automatic Transmissions Part 1: A Cursory History, manufacturers accomplished this by calculation additional gears. Using General Motors as an instance, for the forepart-wheel-drive platforms they went from the 4-speed 4T40-E and 4T65-Due east to a 6-speed 6T70 in 2007 for V-vi applications and 6T30/40 in 2008. For the rear-wheel-drive platforms, they started upgrading the four-speed 4L60-E to 6-speed 6L80 in 2006, then to the eight-speed 8L90 in 2014 and finally to the 10-speed 10L90 in 2017. Other manufacturers of class followed a like path of progression of adding gears to ameliorate vehicle efficiency.

Jason Larochelle is a Sonnax product back up representative. He is a fellow member of the Sonnax TASC Strength (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax technicians.

While Sonnax makes every effort to ensure the accuracy of technical articles at time of publication, we presume no liability for inaccuracies or for information which may become outdated or obsolete over fourth dimension.

Source: https://www.sonnax.com/tech_resources/983-the-evolution-of-automatic-transmissions-part-2-inner-workings-of-hydraulic-planetary-transmissions

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