Group 25 - Transmission

Executive Summary

The demands placed on today's vehicles are immense. They must be able to travel at a wide range of speeds, to back up under their own power, to accelerate quickly, and to tow heavy loads, and they have to do all of these things without destroying the engine inside. It seems simple enough, but try to do every item on that list without changing gears and suddenly things get much more difficult. This is where a transmission comes in. A transmission alters the speed and direction of an output shaft, while allowing it's input shaft to rotate at a fairly constant speed, this allows the engine to remain at it's optimal speed, while allowing the vehicle to travel in the desired direction and speed, greatly reducing engine wear while improving performance and fuel economy. An automatic transmission is a step up from the manual or "standard" transmission. It allows the driver to focus on the road, without being distracted by the continual gear shifting required by a manual transmission. Furthermore, the manual transmission requires much less maintainence and is much harder to damage than a manual transmission. This is important as it provides the consumer with decreased maintainence costs, and increased vehicle reliability.

Introduction

Group Members

• Leo Christian-Tabak
  • Group Leader (organizational duties)
  • Oral Presentation (Presentation and Preparation)
  • Wiki Page
  • Disassembly
  • Reassembly
• Andrew Roberts
  • Disassembly
  • Wiki Page
  • Oral Presentation Preparation
• Tom Svialia
  • Disassembly
  • Reassembly
  • Wiki Page
  • Oral Presentation Preparation
• Vinisha Patel
  • Disassembly
  • Reassembly
  • Wiki Page
• Mike Allen
  • Reassembly
  • CAD Drawings
  • Wiki Page

Product

• Type: Automatic Transmission
• Manufactured by: General Motors
• Type: Hydramatic
• Non Working
  • Severe damage to housing and cover plate.
  • Drained of all fluids and lubricants.
  • Bent drive shaft couple.
  • Missing output shaft.
  • Missing bolts.
  • Shattered disc.
  • Rusting on several components.
  • Detached control cable (no apparent way to re-attach).

The automatic transmission's function is to change the speed and direction of an output shaft, while allowing the input shaft to remain within a small speed range. Most commonly used in vehicles, this device protects against engine wear, allows for greater acceleration, allows the engine to disconnect from the wheels, allows the vehicle to stop and reverse direction, and provides increased performance and fuel economy. This is done by activating or deactivating sets of discs called Clutch Packs which change which gears in the transmission receive power, thereby changing the speed or direction of the output shaft.

Before Disassembly

The transmission was given to us in a non-working state. The transmission had sustained severe damage to the main body, in the form of a large crack encircling the point where it connected to the engine. There was a somewhat deep dent running the length of cover plate A. A disc shaped part inside the transmission had shattered beyond the point where we could determine it's function. The transmission had been drained of all working fluids. The transmission requires electrical power to operate and the corresponding power supply was not provided. There were several bolts missing from one of the cover plates.

The purpose of the product is to variate the speed and direction of the output shaft, while allowing the engine to remain in its optimal range of speeds.

The transmission is made up of the following materials:

• Steel
• Aluminum
• Cast Iron
• Copper
• Plastic
• Filter Material

Disassembly Procedure

We broke the transmission down into four distinct sections, each having it's own purpose.

Click on any picture for full-size image

Before disassembly:

Section 1

Purpose: Park and fluid filtration.

Step #	Procedure	Tools Used	Picture
1	Remove cover plate and 16 Bolts	13mm socket wrench
2	Remove filter	None, held in by friction
3	Remove filter bracket	13mm socket wrench
4	Remove parking lock actuator bracket	13mm socket wrench
5	Remove parking lock actuator rod	No tools required
6	Remove valve cover	10mm socket wrench
7	Remove valve piston	No tools required
8	Remove short metal tube	13mm socket wrench
9	Remove long metal tube, plastic cover, metal clip	13mm socket wrench
10	Remove parking latch	Needle nose pliers

Section 2

Purpose: Fluid control and distribution.

Step #	Procedure	Tools Used	Difficulty (1-5)	Picture
1	Remove cover plate	13mm socket wrench	1
2	Remove Valve Actuator	10mm socket wrench	1
3	Remove small cover plate	13mm and 10mm socket wrenches	1
4	Remove hydraulic block	10mm Socket wrench	1
5	Remove shattered disk	No tools required	1
6	Remove valve body	10mm socket wrench	2
7	Remove hinged ring assembly	Pliers (something to hold the spring in compression)	2
8	Remove hydraulic valve assembly	Circular punch (to remove retaining pin)	1
9	Remove hydraulic valve assembly	Circular punch (to remove retaining pin)	1
10	Remove valve body backplate	13mm socket wrench	2

Section 3

Purpose: Speed and direction control.

Step #	Procedure	Tools Used	Difficulty (1-5)	Picture
1	Remove chain, gears, and spurred shaft	No tools required	1
2	Remove pin from parking lock actuator gear	Cylindrical punch and hammer	3
3	Remove parking lock actuator shaft, gear, and push rod.	No tools required	2
4	Remove plastic cap	No tools required	1
5	Remove retaining plate	No tools required	1
6	Remove clutch pack	No tools required	1
7	Remove clutch pack retaining ring	Pliers, screwdriver	2
8	Remove clutch pack clutch rings	No tools required	1
9	Remove inner clutch pack	No tools required	1
10	Remove clutch pack retaining ring	Pliers, Screwdriver	2
11	Remove clutch pack clutch rings	No tools required	1
12	Remove locking belt	No tools required	1
13	Remove ring gear	No tools required	1
14	Remove planetary gear set	No tools required	1
15	Remove sun gear from planetary gear set	No tools required	1
16	Remove bell shaped housing	No tools required	1
17	Remove short shaft	No tools required	1
18	Remove gear train retaining ring	Pliers, Screwdriver	2
19	Remove spring loaded metal plate	No tools required	4
20	Remove circular bearing	No tools required	1
21	Remove planetary gear set	No tools required	1
22	Remove clutch pack retaining ring	Pliers, Screwdriver	3
23	Remove clutch pack clutch rings	No tools required	1
24	Remove ring bearing	No tools required	1
25	Remove spacer ring	No tools required	1
26	Remove ring gear	No tools required	1
27	Remove spurred shaft	No tools required	1
28	Remove inner retaining ring	Pliers, Scredriver	4
29	Remove indented ring	Pliers, Screwdriver	2
30	Remove ring bearing	No tools required	1
31	Remove ring gear	No tools required	1
32	Remove sun gear	No tools required	1
33	Remove planetary/reversal gear housing	No tools required	1

Section 4

Purpose: Speed/Direction sensor providing feedback to vehicle.

Step #	Procedure	Tools Used	Difficulty (1-5)	Picture
1	Remove cover plate and attached electronics	4.5mm wrench	2
2	Remove speed sensor housing	10mm socket wrench	1
3	Remove speed sensor shaft	No tools required	1

After Disassembly

Most of the components inside the transmission were made out of steel. There were also a few plastic parts (such as the gaskets) and one rubber hose on the external frame of the transmission. Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight. Carbon is the most cost-effective alloying material for iron. Carbon acts as a hardening agent, preventing dislocations in the iron atom. The reason why steel was used for the majority of the parts is because steel can take the tremendous stresses present during operation. The fact that steel is competitively priced means it is easy to obtain and also cheaper if bought in bulk; reducing production costs.

Plastic was used for many of the non load-bearing parts because it is light, inexpensive, corrosion resistant, and easy to manufacture.

Aluminum was also used for a lot of the parts of the transmission. It is common in the automotive industry to make parts using the Aluminum die casting method, because making parts in this way is inexpensive. Also the properties of Aluminum make it lightweight and strong. The fact that it is one third the weight of steel makes it an ideal component for many cars today. Aluminum is corrosion resistant and also extremely durable. They are necessary in the production of cars today because it tremendously reduces the weight of the car, increasing performance and fuel economy.

Part Table

Name	Number	Material	Manufacturing Process	Image
Cover Plate	1	Aluminum	Casting
Filter	1	Aluminum, Plastic, Filter material	Injection Molding (Plastic), Sheet metal forming (Aluminum), Unknown (filter)
Filter Bracket	1	Steel	Casting
Parking lock actuator bracket	1	Steel	Casting
Parking lock actuator rod	1	Steel	Machining
Valve Cover	1	Steel	Casting
Gasket	1	Plastic	Injection Molding
10mm Bolt (3/4" long)	4	Steel	Machining
Tube clip	1	Aluminum	Sheet metal forming
Valve	1	Steel	Machining
Short tube	1	Steel	Extrusion and bending
Plastic Cap	1	Plastic	Injection Molding
Metal Clip	1	Aluminum	Sheet metal forming
Tube Clip	1	Aluminum	Sheet metal forming
13mm Bolt (1/2" long)	1	Steel	Machining
Long Tube	1	Steel	Extrusion
Parking lock	1	Steel	Casting
Return Spring	1	Steel	Extrusion
Hinge Pin	1	Steel	Machining
Retaining clip	1	Steel	Extrusion
13mm Bolt 1”	16	Steel	Machining
Washers	16	Steel	Machining
Throttle Cable	1	Plastic, Rubber, Steel	Extrusion, Injection Molding	200px
13mm Bolt (1" Long)	11	Steel	Machining
Back Cover Plate	1	Steel	Casting
10mm Bolt 1 ¾”	1	Steel	Machining
10mm Bolt 2 ½”	1	Steel	Machining
Valve Lever Actuator	1	Steel	Sheet Metal Forming
10mm Bolt 1”	3	Steel	Machining
10mm Bolt 3 ½”	4	Steel	Machining
13mm Bolt 5 1/12”	1	Steel	Machining
Backplate	1	Steel	Casting
Hydraulic Block With Solenoid	1	Steel	Casting, Machining
Valve Housing	1	Steel	Casting
Shattered Disk (not shown)	1	Steel	Casting, Machining
Ring Gasket	1	Rubber	Injection Molding
Ring with tab	1	Steel	Casting, Machining
Spring	1	Steel	Extrusion
Hinge Pin	1	Steel	Extrusion, Machining
13mm Bolt 1 ½”	1	Steel	Machined
13mm Bolt 2 1/4”	1	Steel	Machined
13mm Bolt 2 ½”	1	Steel	Machined
10mm Bolt 2 ½”	1	Steel	Machined
Valve Retaining Pin	6	Steel	Sheet metal forming
Valve assembly	6	Steel	Extrusion, Machining, Bending
Gasket	1	Steel	Sheet Metal Forming	200px
Gasket	1	Plastic	Sheet Forming	200px
13mm Bolt 1”	7	Steel	Machining
13mm Bolt 1 1/4”	5	Steel	Machining
Valve body backplate	1	Steel	Casting, Machining
Valve (not seen, fits in central hole)	1	Steel	Machining
Valve pin (Not seen, fits in central hole)	1	Steel	Machining
Speed Sensor Cover Plate	1	Steel	Casting, Machining
Speed Sensor	1	Copper, Plastic, Iron Magnet	Injection Molding (plastic), Unknown (circuitry)
5mm Bolt 1/2"	4	Steel	Machining
Speed Sensor Housing	1	Steel	Casting, Machining
10mm Bolt 1/2"	2	Steel	Machining
Speed Sensor Shaft	1	Plastic, Steel	Injection Molding, Extrusion, Machining, Sheet Metal Forming
Engine drive shaft	1	Steel	Machining
Drive Gear	2	Steel	Casting, Machining
Chain	1	Steel	Sheet Metal Forming (links), Extrusion (connecting pins)
Output Shaft	1	Steel	Extrusion, Machining
Parking lock actuator pushrod	1	Steel	Extrusion
Pushrod gearstop	1	Steel	Machining
Parking lock actuator shaft	1	Steel	Extrusion
Set pin	1	Steel	Sheet Metal Forming
Retaining plate	1	Steel	Casting, Machining
Clutch pack	1	Steel	Machining
Retaining ring	1	Steel	Extrusion
Clutch rings	11	Steel	Machining
Inner clutch pack	1	Steel	Casting, Machining
Retaining ring	1	Steel	Casting, Machining
Clutch rings	9	Steel	Casting, Machining
Locking belt	1	Steel	Sheet Metal Forming
Ring gear	1	Steel	Casting, Machining
Planetary gear set	1	Steel	Casting, Machining, Sheet Metal Forming
Sun gear	1	Steel	Casting, Machining
Clutch assembly housing	1	Steel	Injection Molding
Hollow geared shaft	1	Steel	Casting, Machining
Retaining ring	1	Steel	Extrusion
Spring loaded plate	1	Steel	Casting, Machining
Ring bearing	1	Steel	Sheet Metal Forming, Machining
Planetary gear set	1	Steel	Casting, Machining
Retaining ring	1	Steel	Extrusion
Clutch rings	11	Steel	Machined
Ring bearing	1	Steel	Sheet Metal Forming, Machining
Spacer ring	1	Steel	Sheet Metal Forming
Ring gear	1	Steel	Casting, Machining
Hollow spurred shaft	1	Steel	Casting, Machining
Retaining ring	1	Steel	Extrusion
Locking belt	1	Steel	Sheet Metal Forming
Ring bearing	1	Steel	Sheet Metal Forming, Machining
Ring gear	1	Steel	Casting, Machining
Sun gear	1	Steel	Casting, Machining
Reversal and orbital gear set	1	Steel	Casting, Extrusion, Machining

CAD Drawings

Part	Drawing
Assembled Bearing:
Bearing Base:
Bottom:
Top:
Drive Shaft:

Assembly

The assembly of the product was almost the exact reverse order of dis-assembly, since there is some flexibility in the order in which some parts can be re-attached. During re-assembly, we discovered that it was easier to assemble the section between the bell shaped housing, and the outer clutch pack first, and then slide the entire assembly into the transmission. This is different from dis-assembly, where each piece came out independently.

We came across a few difficulties while trying to assemble the transmission. The difficulty came with placing the retaining rings back in the transmission body, and with replacing the spring loaded disk. We struggled getting the retaining rings out during dis-assembly and again during re-assembly. The problem was that we did not have the correct tools to push back the compression rings into their correct slots and so we had to be innovative and use pliers and screw drivers to get the rings in. This proved to be quite a challenge but it gave us a better understanding as to why they need to be fitted in so tightly. It explained the complexity of this transmission and put the job at hand into context.

As mentioned before, the tools that were needed, such as a ring compression tool, were not available to us so instead what we ended up using was a pair of needle nose pliers and several different different screw drivers. What we did was forced the compression rings into place while one or two people compressed the rings using these needle nose pliers. It was a great group achievement once the rings fitted into place.

After Assembly

The automatic transmission is probably one of the least understood transmission designs, as its design is very different from that of a manual transmission. Much of the confusion likely stems from the fact that automatic transmissions are thought by many to have "gears" in the same way that a manual transmission does. While an automatic transmission does have the standard settings, Drive, Reverse, 3, 2, 1, Neutral, and Park, these settings do not engage gears in the way one might think. The two main differences between an automatic and manual transmission is that the automatic has no clutch pedal and most importantly, no gear shift. With an automatic transmission, once it is placed into drive mode, nothing else has to be done for the car to move. An automatic transmission varies it's speed and direction with clutch packs.

A clutch pack

When transmission fluid pressure is routed to a clutch pack, it compresses the clutch rings, preventing them from sliding past each other. You may notice that the clutch rings alternate, with teeth pointing out or in. When the rings lock, the inner section and the outer section turn together, sending power to a different sun, planetary, or ring gear. In our transmission, there were three orbital gear sets (Sun, Planetary, Ring), although this number varies depending on transmission design. By engaging or disengaging clutch packs, the transmission can control the speed and direction of the ring and planetary gears connected to the output shaft. This is how the automatic transmission "shifts gears". Since an orbital gear set is essentially a mechanical speed comparator, by varying the speed and direction of the planetary gear, the sun gear, or both, the transmission can create different gear "ratios" with fewer moving parts than a manual transmission. The following video shows the operation of an automatic transmission.

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When researching for the oral report, we discovered that the transmission was actually missing a critical component. The torque converter, which acts as the clutch for an automatic transmission was not given to us with the transmission. Without it, the transmission has no way to disengage from the engine when shifting. The torque converter is essentially two propellers facing each other. The propellers are surrounded in a fluid to keep mechanical loss to a minimum. When one propeller spins, it pushes the fluid through the second, providing power to the transmission. When the transmission changes gears, the increased resistance simply slows the second propeller, while allowing the first to continue spinning, eliminating the need for a movable clutch plate.

It became clear to us during dis-assembly that the transmission was meant for a front-wheel-drive vehicle. This is evident by the presence of holes for two output shafts, although the product only came with one output shaft. Also, the transmission housing is designed to mount an engine directly on top of it, rather than on the end.

Probably the most significant design change we would recommend is the increased use of aluminum or lightweight parts. The transmission is extremely heavy, even with sections 1 and 2 completely removed. A lighter transmission would provide increased performance and fuel economy, as the engine would not have to move as much weight. The second recommendation we would make would be to replace the set pin connecting the parking lock actuator components with a set screw, or keyed shaft. During dis-assembly, we spent nearly two hours trying to remove the pin ourselves, before bringing the transmission to the machine shop to have the pin removed for us. During re-assembly we encountered problems as well, since the pin is set facing into the transmission body (when assembled) making it very difficult to remove or re-attach. A set screw or keyed shaft would eliminate this problem with no loss of joint strength. The third recommendation we would suggest would be to replace the bolts holding down the speed sensor cover plate with a larger size. During dis-assembly, we nearly stripped the bolt heads trying to get them off. A larger size would eliminate the possibility of stripping with only a marginal increase in weight.

How an automatic transmission works

This product that we were given is one of two types of transmission systems. There is an automatic and manual transmission. The two main differences between an automatic and manual transmission is that the automatic has no clutch pedal and most importantly, no gear shift. With an automatic transmission, once it is placed into drive mode, nothing else has to be done for the car to move. It is the transmission that allows a car to have gears and thus have variate speeds. It is also the one piece in a car that makes more effective use of the engines torque; achieving better efficiency in the long run. Without a transmission in a car assembly, the car engine would not have different speeds. Focusing more on automatic transmissions, different gears are not locked and unlocked; simply the same set of gears are used. The device which makes an automatic transmission possible is the planetary gearset. This small piece creates the different gear ratios. We must understand to an extent the vital role this tiny planetary gearset plays in the transmission. To put it into context, everything in the transmission is there just to aid the planetary gearset. It is one of many of the main components of an automatic transmission system. The modern automatic transmission consists of many components and systems that are designed to work together in a symphony of clever mechanical, hydraulic and electrical technology that has evolved over the years.

THE MAIN COMPONENTS INCLUDE

-The planetary gearset: These parts are the mechanical systems that provide the various forward gear ratios as well as reverse.

-A hydrolic system: This uses a special transmission fluid sent under pressure by an oil Pump through the valve Body to control the clutches and the bands in order to control the planetary gear sets.

-Seals and gaskets: Are used to keep the oil where it is supposed to be and prevent it from leaking out.

-The Torque Converter: This acts like a clutch to allow the vehicle to come to a stop in gear while the engine is still running.

-Large gear pump: What this does is move the transmission fluid around (we did not have this inside our transmission,

-Set of bands: The role of these is to lock parts of a gearset

-Wet plate clutches: This means the clutch runs in a bath of oil and thus gives better performance in getting the car to a smooth stop. Dry plate clutches run dry with no oil and thus more maintenance required.

Since the transmission was given to us damaged and drained of fluids, it remained inoperable when re-assembled. We discovered that many crucial parts were missing once we disassembled; including the gear pump.

This video shows how an automatic transmission works: <object width="640" height="505"><param name="movie" value="http://www.youtube.com/v/LM6eyXSGGaE&hl=en&fs=1&color1=0x2b405b&color2=0x6b8ab6"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/LM6eyXSGGaE&hl=en&fs=1&color1=0x2b405b&color2=0x6b8ab6" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="505"></embed></object> <embed src="http://www.youtube.com/watch?v=LM6eyXSGGaE" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="600" height="500"></embed>

Power flow of an automatic transmission system

The power flow is pretty straightforward. Mechanical power from the engine is delivered to the transmission through the torque converter. Then through the transmission and drive shaft, it reaches the final drive where it is split into two and delivered to the two back wheels (this is assuming it is a rear wheel drive and so no mechanical power is delivered to the front wheels)

== The significance of a transmission ==

It is the device that is connected to the back of the engine and it sends the power produced from the engine to the drive wheels and depending on what kind of wheel drive it is (four wheel or two wheel drive), it will make the wheels rotate. The transmissions job is to make sure the power supplied by the engine is delivered to the wheels. This is primarily done through gear combination's. When the transmission is in neutral position, it disconnects the engine from the drive wheels, thus the car can back up as the wheels are now free to rotate in the opposite direction. It is the drive shaft which connects the rear of the transmission to the final drive which is found at the back of the rear axle (used to send power to the rear wheels). Without the presence of a transmission the engine would have no effect on the wheels of the car, thus no movement.

References

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