Group 25 - Transmission

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Contents

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:

Trans1.jpg

Section 1

Purpose: Park and fluid filtration.

Step # Procedure Tools Used Picture
1 Remove cover plate and 16 Bolts 13mm socket wrench Trans2.jpg
2 Remove filter None, held in by friction Trans3.jpg
3 Remove filter bracket 13mm socket wrench Trans4.jpg
4 Remove parking lock actuator bracket 13mm socket wrench Trans5.jpg
5 Remove parking lock actuator rod No tools required Trans6.jpg
6 Remove valve cover 10mm socket wrench Trans7.jpg
7 Remove valve piston No tools required Trans8.jpg
8 Remove short metal tube 13mm socket wrench Trans9.jpg
9 Remove long metal tube, plastic cover, metal clip 13mm socket wrench Trans10.jpg
10 Remove parking latch Needle nose pliers Trans11.jpg

Section 2

Purpose: Fluid control and distribution.

Step # Procedure Tools Used Difficulty (1-5) Picture
1 Remove cover plate 13mm socket wrench 1 Trans21.jpg
2 Remove Valve Actuator 10mm socket wrench 1 Trans22.jpg
3 Remove small cover plate 13mm and 10mm socket wrenches 1 Trans23.jpg
4 Remove hydraulic block 10mm Socket wrench 1 Trans24.jpg
5 Remove shattered disk No tools required 1
6 Remove valve body 10mm socket wrench 2 Trans25.jpg
7 Remove hinged ring assembly Pliers (something to hold the spring in compression) 2 Trans26.jpg
8 Remove hydraulic valve assembly Circular punch (to remove retaining pin) 1 Trans27.jpg
9 Remove hydraulic valve assembly Circular punch (to remove retaining pin) 1 Trans28.jpg
10 Remove valve body backplate 13mm socket wrench 2 Trans29.jpg

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 Trans30.jpg
2 Remove pin from parking lock actuator gear Cylindrical punch and hammer 3 Trans31.jpg
3 Remove parking lock actuator shaft, gear, and push rod. No tools required 2 Trans32.jpg
4 Remove plastic cap No tools required 1 Trans33.jpg
5 Remove retaining plate No tools required 1 Trans34.jpg
6 Remove clutch pack No tools required 1 Trans35.jpg
7 Remove clutch pack retaining ring Pliers, screwdriver 2 Trans36.jpg
8 Remove clutch pack clutch rings No tools required 1 Trans37.jpg
9 Remove inner clutch pack No tools required 1 Trans38.jpg
10 Remove clutch pack retaining ring Pliers, Screwdriver 2 Trans39.jpg
11 Remove clutch pack clutch rings No tools required 1 Trans310.jpg
12 Remove locking belt No tools required 1 Trans311.jpg
13 Remove ring gear No tools required 1 Trans312.jpg
14 Remove planetary gear set No tools required 1 Trans313.jpg
15 Remove sun gear from planetary gear set No tools required 1 Trans314.jpg
16 Remove bell shaped housing No tools required 1 Trans315.jpg
17 Remove short shaft No tools required 1 Trans316.jpg
18 Remove gear train retaining ring Pliers, Screwdriver 2 Trans317.jpg
19 Remove spring loaded metal plate No tools required 4 Trans318.jpg
20 Remove circular bearing No tools required 1 Trans319.jpg
21 Remove planetary gear set No tools required 1 Trans320.jpg
22 Remove clutch pack retaining ring Pliers, Screwdriver 3 Trans321.jpg
23 Remove clutch pack clutch rings No tools required 1 Trans322.jpg
24 Remove ring bearing No tools required 1 Trans323.jpg
25 Remove spacer ring No tools required 1 Trans324.jpg
26 Remove ring gear No tools required 1 Trans325.jpg
27 Remove spurred shaft No tools required 1 Trans326.jpg
28 Remove inner retaining ring Pliers, Scredriver 4 Trans327.jpg
29 Remove indented ring Pliers, Screwdriver 2 Trans328.jpg
30 Remove ring bearing No tools required 1 Trans329.jpg
31 Remove ring gear No tools required 1 Trans330.jpg
32 Remove sun gear No tools required 1 Trans331.jpg
33 Remove planetary/reversal gear housing No tools required 1 Trans332.jpg

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 Trans41.jpg
2 Remove speed sensor housing 10mm socket wrench 1 Trans42.jpg
3 Remove speed sensor shaft No tools required 1 Trans43.jpg

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 Trans1.jpg
Filter 1 Aluminum, Plastic, Filter material Injection Molding (Plastic), Sheet metal forming (Aluminum), Unknown (filter) Trans2.jpg
Filter Bracket 1 Steel Casting Trans103.jpg
Parking lock actuator bracket 1 Steel Casting Trans103.jpg
Parking lock actuator rod 1 Steel Machining Trans6.jpg
Valve Cover 1 Steel Casting Trans104.jpg
Gasket 1 Plastic Injection Molding
10mm Bolt (3/4" long) 4 Steel Machining
Tube clip 1 Aluminum Sheet metal forming
Valve 1 Steel Machining Trans105.jpg
Short tube 1 Steel Extrusion and bending Trans106.jpg
Plastic Cap 1 Plastic Injection Molding Trans107.jpg
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 Trans108.jpg
Parking lock 1 Steel Casting Trans109.jpg
Return Spring 1 Steel Extrusion
Hinge Pin 1 Steel Machining
Retaining clip 1 Steel Extrusion
13mm Bolt 1” 16 Steel Machining Trans110.jpg
Washers 16 Steel Machining
Throttle Cable 1 Plastic, Rubber, Steel Extrusion, Injection Molding 200px
13mm Bolt (1" Long) 11 Steel Machining Trans110.jpg
Back Cover Plate 1 Steel Casting Trans117.jpg
10mm Bolt 1 ¾” 1 Steel Machining Trans120.jpg
10mm Bolt 2 ½” 1 Steel Machining
Valve Lever Actuator 1 Steel Sheet Metal Forming
10mm Bolt 1” 3 Steel Machining Trans124.jpg
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 Trans125.jpg
Valve Housing 1 Steel Casting Trans126.jpg
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 Trans131.jpg
Valve assembly 6 Steel Extrusion, Machining, Bending
Gasket (not shown) 1 Steel Sheet Metal Forming Trans132.jpg
Gasket (not shown) 1 Plastic Sheet Forming
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 Trans134.jpg
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 Trans133.jpg
10mm Bolt 1/2" 2 Steel Machining
Speed Sensor Shaft 1 Plastic, Steel Injection Molding, Extrusion, Machining, Sheet Metal Forming Trans133a.jpg
Engine drive shaft 1 Steel Machining Trans135.jpg
Drive Gear 2 Steel Casting, Machining
Chain 1 Steel Sheet Metal Forming (links), Extrusion (connecting pins)
Output Shaft 1 Steel Extrusion, Machining Trans136.jpg
Parking lock actuator pushrod 1 Steel Extrusion Trans137.jpg
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 Trans140.jpg
Clutch pack 1 Steel Machining Trans141.jpg
Retaining ring 1 Steel Extrusion Trans142.jpg
Clutch rings 11 Steel Machining Trans143.jpg
Inner clutch pack 1 Steel Casting, Machining Trans144.jpg
Retaining ring 1 Steel Casting, Machining Trans145.jpg
Clutch rings 9 Steel Casting, Machining
Locking belt 1 Steel Sheet Metal Forming Trans147.jpg
Ring gear 1 Steel Casting, Machining Trans148.jpg
Planetary gear set 1 Steel Casting, Machining, Sheet Metal Forming Trans149.jpg
Sun gear 1 Steel Casting, Machining Trans150.jpg
Clutch assembly housing 1 Steel Injection Molding Trans151.jpg
Hollow geared shaft 1 Steel Casting, Machining Trans152.jpg
Retaining ring 1 Steel Extrusion Trans153.jpg
Spring loaded plate 1 Steel Casting, Machining Trans154.jpg
Ring bearing 1 Steel Sheet Metal Forming, Machining Trans155.jpg
Planetary gear set 1 Steel Casting, Machining Trans156.jpg
Retaining ring 1 Steel Extrusion Trans157.jpg
Clutch rings 11 Steel Machined Trans158.jpg
Ring bearing 1 Steel Sheet Metal Forming, Machining Trans159.jpg
Spacer ring 1 Steel Sheet Metal Forming Trans160.jpg
Ring gear 1 Steel Casting, Machining Trans161.jpg
Hollow spurred shaft 1 Steel Casting, Machining Trans162.jpg
Retaining ring 1 Steel Extrusion Trans163.jpg
Locking belt 1 Steel Sheet Metal Forming Trans164.jpg
Ring bearing 1 Steel Sheet Metal Forming, Machining Trans165.jpg
Ring gear 1 Steel Casting, Machining Trans166.jpg
Sun gear 1 Steel Casting, Machining Trans167.jpg
Reversal and orbital gear set 1 Steel Casting, Extrusion, Machining Trans168.jpg

CAD Drawings

Part Drawing
Assembled Bearing: Assembled Bearing (25).jpg
Bearing Base: Bearing Base (25).jpg
Bottom: Bottom (25).jpg
Top: Top (25).jpg
Drive Shaft: C7 (25).jpg

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

Trans142.jpg

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 and manufacture of an automatic transmission.

<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>


The following applet shows the engagement and disengagement of clutch packs for different gears.

<embed src="http://static.howstuffworks.com/flash/automatic-transmission-gears-diagram.swf" type="application/x-shockwave-flash" allowscriptaccess="always" width="640" height="505"></embed>


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.

References

Karem, Nice. "How Automatic Transmissions Work"

    http://auto.howstuffworks.com/automatic-transmission1.htm