Servic

e M

an

ual

Service Manual

THIS IS A MANUAL PRODUCED BY JENSALES INC. WITHOUT THE AUTHORIZATION OF

CATERPILLAR OR IT’S SUCCESSORS. CATERPILLAR AND IT’S SUCCESSORS

ARE NOT RESPONSIBLE FOR THE QUALITY OR ACCURACY OF THIS MANUAL.

TRADE MARKS AND TRADE NAMES CONTAINED AND USED HEREIN ARE THOSE OF OTHERS,

AND ARE USED HERE IN A DESCRIPTIVE SENSE TO REFER TO THE PRODUCTS OF OTHERS.

7155 Truck

Transmission

S/n 56K1 & Up

CT-S-7155 TRAN

SERVICE MANUAL

7155 TRANSMISSION SERIAL NUMBERS 56K1-UP

FORM NO. SENR7002

, )

7155 TRANSMISSION INDEX

SYSTEMS OPERATION

Gear Group ........................................ 15 Design .......................................... 15 Lubrication ...................................... 21 Operation ....................................... 17

General Information .................................. 5

Input Clutch and Input Brake .......................... 10 I nput Brake ..................................... 12 I nput Clutch ..................................... 11 Lubrication ...................................... 13

Output Clutch and Output Brake ........................ 22 Lubrication ...................................... 24 Output Brake ..........•......................... 23 Output Clutch ................................... 22

Transmission Components ........................•..... 6

Transmission Control and Ratio Selector .................. 25 Air Charging System ............................... 27 Air System for Shift Forks ......•................... 28

Air System for Shift Forks (A), (D), and (1:;) ..••.•••••. 28 Air System for Shift Forks (B) and (e) ............... 31 Air System in Neutral ............................ 38 Mechanically Operated Valve Position ................ 38

Check Valves .................................... 26 Pressure Regulator ................................ 42 Quick Fill Valve .................................. 45 Ratio Selection ................................... 45 Sensing Circuit ................................... 40 Shift Cycle Circuit ........................•.•..... 46 Two Position, Three Way Valves ...................... 25

Transmission Operation .............................•.. 8

TESTING AND ADJUSTING

Air Tests for Clutches and Brakes ....................... 62 Flywheel and Flywheel Housing ..................... 63,64

Pressure Regulator Adjustment ....................••... 62 Troubleshooting ...............•.•........•........ 66·90

DISASSEMBLY AND ASSEMBLY

Transmission Gears and Clutches, Assemble ............... 106 Transmission Gears and Clutches, Disassemble .............. 92

Transmission Ratio Selector, Assemble ................•. 126 Transmission Ratio Selector, Disassemble ...........•.... 122

SPECIFICATIONS

Brake Group ...................................... 133 Front Clutch Group ................................. 132 General Tightening Torques ........................... 131 Rear Clutch Group ............................ " 135,136

Transmission Control Group .............•.•...•...•.. 134 Transmission Gear Group .................•...•....... 134 Transmission Ratio Selector ............•...... 137,138,139

3

OUTPUT CLUTCH AND OUTPUT BRAKE SYSTEMS OPERATION

OUTPUT CLUTCH AND OUTPUT BRAKE

OUTPUT CLUTCH AND BRAKE

1. Plate. 10. Hub. 2. Plate. 11. Plate. 3. Plate. 12. Piston. 4. Plate. 13. Output shaft. 5. Plate. 14. Gear group. 6. Disc. 15. Hub. 7. Piston. 16. Thrust bearing. 8. Cover. 17. Ring. 9. Disc. 18. Spring.

OUTPUT CLUTCH

The output clutch connects the gear group (14) of the transmission to the output shaft (13). This clutch uses 13 discs (6) with a "paper" friction material and 12 or more (for the adjustment of clutch thickness) steel plates (5). The clutch discs and plates are made cool by oil.

The hub (15), ring (17), discs (6), and plate (11) are connected to and turn with the gear group (14). The plates (5) and hub (10) are connected to the output shaft (13) of the transmission.

The clutch is engaged by air pressure (sent from the transmission control) working between plate (1) and piston (12). This air pressure moves the piston to the right.

22

As the piston (12) that does not turn moves to the right, it moves the turning plate (11) through a thrust bearing (16). This plate (11) will move to the right until the plates (5) and discs (6) of the clutch are held together. Now the hub (10) is con­nected to the ring (17) and power can go from the gear group (14) to the output shaft (13) of the transmission.

5 S

OUTPUT CLUTCH ENGAGED

1. Plate. 5. Plate. 6. Disc. 10. Hub. 11. Plate. 12. Piston. 13. Output shaft. 14. Gear group. 15. Hub. 16. Thrust bearing. 17. Ring.

10

The pressure of the air sent to the output clutch is controlled by a pressure regulator. The pressure in 1st through 4th speed is 92 psi (6.5 kg/cm2 ), in 5th through 8th speed it is 74 psi (5.2 kg/cm2 ), in 9th through 12th speed it is 37 psi (2.6 kg/cm2 ),

and in 13th through 16th speed it is 19 psi (1.4 kg/cm2 ). The air pressure is higher when the torque sent through the clutch is higher (the lower the gear ratio, the higher the torque). The pressure regulator keeps the output clutch from getting more air pressure than necessary.

PRESSURE REGULATOR, CLUTCHES AND BRAKES

PRESSURE REGULATOR ADJUSTMENT

1. Connect an air pressure gauge to the gauge hole (1) for the output clutch.

2. Start the engine.

3. Put the selector lever in 16th speed.

4. The pressure reading must be 19 ± 2 psi (1.4 ± 0.1 kg/cm2 ) with 120 psi (8.4 kg/cm2 )

air pressure (truck air) to the transmission control.

5. The air pressure to the output clutch can be adjusted by the addition or removal of shims (2) in the pressure regulator.

PRESSURE CHANGE TO THE OUTPUT CLUTCH BY THE ADDITION OF REMOVAL OF ONE SHIM

Thickness Change In Shim

Part No. in. mm psi kg/cm2

9N1574 .010 0.25 1 0.07

9N1575 .030 0.76 3 0.21

NOTE: With 90 psi (6.3 kg/cm2 ) air pressure (shop air) to the transmission control, the pressure read­ing must be 22.4 ± 2 psi (1.6 ± 0.1 kg/cm2 ).

AIR TESTS FOR CLUTCHES AND BRAKES

Shop air can be put into the transmission hous­ing to operate the clutches and brakes one at a time. This test is used to find leaks in a clutch or brake. It does not test the transmission controls for correct operation.

Remove the transmission controls and put pres­sure air into the correct hole for each clutch or brake one at a time. A large air leak inside the transmission gives the indication that the specific clutch or brake has damaged seals. Make the neces­sary repairs.

NOTE: There are two holes (4) and (5) that go to the output clutch. One of these holes must have a plug on it during the test of the output clutch.

62

TESTING AND ADJUSTING

0 0 0 0

0 0 0 (()

0 0 0 0

)~~P o 0 ~I}ls (- BRAKE

0 0 0

0 0 0 0

~ 0 CLUTCH

0

0 0 0

PRESSURE ADJUSTMENT FOR OUTPUT CLUTCH

1. Gauge hole. 2. Shims.

AIR HOLES FOR CLUTCHES AND BRAKES

1. Output brake hole. 2. Input clutch hole. 3. Input brake hole. 4. Output clutch hole. 5. Output clutch hole.

2

7155 TRUCK TRANSMISSION DISASSEMBLY AND ASSEMBLY

TRANSMISSION GEARS AND CLUTCHES 110. Remove spacers (158) from the three

coun tershafts.

111. Remove plate (160) from the rear case.

112. Remove three bearings (159) from the plate with tooling (C).

113. Remove shifting fork (144). Remove collar (161) from the shaft.

114. Put a mark with paint on the three counter­shafts and gear (164) to show location of the countershafts in the gear.

115. Put a strap or rope around the three countershafts. Fasten a hoist to the strap or rope. Remove three countershafts (162) and the gears as a unit.

116. Put the countershafts and gears on the floor. Make a separation of the counter­shafts from the gears. Remove the collar from the gear in the center.

117. Remove bearing race (163) from each end of the three countershafts with tooling (B).

118. Remove gear (165) and shaft (167). Re­move the collar from the shaft.

119. Remove three bearings (166) from the rear case with tooling (C).

104