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| Illustration 1 | g01380250 |
The transmission control system for oil and gas is required to support an OEM application with 12 volt or 24 volt system voltage. The hardware for the transmission is dependent on the system voltage. The start relay and transmission solenoids must be selected in order to operate with system voltage.
Overview
The Electronic Control Unit (ECU) controls different systems on the machine. The following information is an overview of the systems that are controlled by the ECU.
The ECU controls the transmission shift points. The basic components and corresponding requirements for shifting of the transmission are listed below:
Shift pad - The ECU must know the current gear position. The sensor for the shift lever provides a J1939 signal. The J1939 signal varies with the gear that has been selected.
Transmission Output Speed Sensor (TOS) - The ECU must know the output speed of the transmission. The TOS sensor provides this information via the output shaft.
When the operator selects a forward gear the ECU automatically shifts the transmission. The shift is dictated by the transmission output speed in automatic mode. In power shift mode, the shift is determined by operator input via the shift pad. The automatic shift points are stored in the ECU. A shift occurs when the transmission output speed matches the shift point. When the TOS increases to a shift point the ECU activates the proper solenoids in order to change the transmission gear.
Note: The transmission output speed is directly proportional to ground speed and engine speed. This occurs while the transmission is in direct drive. Shift points are based on the calculated engine speed for automatic mode.
The items that follow are exceptions.
- Directional shifts are inhibited if TOS is greater than 150 RPM and engine speed is greater than 1000 RPM. This helps protect the transmission from damaging directional shifts. For additional information, refer to Systems Operation, "Reverse Shift Inhibit Function".
- For automatic mode only. The ECU does not downshift when the operator selects a speed that is not appropriate for the current TOS. Automatic upshifting and/or downshifting will continue. The selected gear now becomes the new top gear.
- For automatic mode only. The ECU shifts the transmission up one gear above the selected gear if the TOS reaches a critical value. This helps protect the engine from overspeed.
The ECU determines if the backup alarm should sound.
The ECU also provides the service technician with enhanced diagnostic capabilities. This is available through the use of onboard memory. Onboard memory stores the possible diagnostic codes for retrieval at the time of service. Service personnel should use the Caterpillar Electronic Technician (Cat ET) for troubleshooting.
The following modules communicate with each other through the SAE J1939 on Tier iii Industrial Engines and On-Highway Engines: the ECU for the transmission, the ECU for the engine and the shifter. The ECU will share data via the SAE J1939 communication link. The instrument cluster receives information from the transmission ECU via the CAN Data Link. The Cat Data Link is used in order to communicate between the ECU for the engine and the ECU for the transmission on all Tier iii industrial engines.
Note: The data link provides the communication between the engine and the transmission. The following conditions will cause intermittent performance of the engine and transmission:disconnected data link, bad connection and too much traffic on the data link.
TH31
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| Illustration 2 | g01943278 |
TH31 (1) Torque converter housing (2) PTO's SAE "B" J744 13 teeth splines (CW rotation, two and four bolt pump mounts), speed ratio 1:1 (3) Lifting eye (4) PTO's SAE "C" J744 14 teeth splines (CCW rotation, two and four bolt pump mounts), speed ratio 1:1 (5) Test port (torque converter lock up clutch) (6) Torque converter output speed sensor (7) Electronic control module (ECM) (8) Transmission output speed sensor (9) Diagnostic connector (10) Customer interface connector (wire harness receptacle) (11) Drop box connector (12) Output yoke (13) Test port (clutch 5 pressure) (14) Test port (clutch 4 pressure) (15) Test port (clutch 3 pressure) (16) Test port (clutch 2 pressure) (17) Test port (clutch 1 pressure) (18) Test port (Torque converter inlet pressure) (19) Relief valve (torque converter inlet pressure) (20) Torque converter inlet temperature sensor (21) Transmission oil filter cover (5 x 7 filter) (22) Test port (transmission supply pressure) (23) Filter bypass valve (24) Test port (transmission filter inlet pressure and scheduled oil sample "SOS" port "1") (25) Filter bypass switch (26) Lifting points (M22 thds) (27) Isolator mounting pad Ø 145 mm (Ø 5.71 inch) (28) Standard mounting bracket (with isolators) for TH31-E61 ( 275-9382 Transmission Mounting Gp ) (29) Customer mounting bolt (M24 X 3 thds) (30) Transmission dry wall mounts (do not remove) (31) Test port (Transmission lube pressure) (32) Oil inlet from cooler 27 mm (1.06 inch) (33) Torque converter outlet temperature sensor (34) Oil outlet to cooler 27 mm (1.06 inch) (35) Test port (converter out pressure and scheduled oil sample "SOS" port "2") (36) Transmission identification plate (37) Magnetic pickup (38) Transmission filler tube and dipstick | |
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| Illustration 3 | g01943280 |
Rear view (39) Engine output speed sensor (40) Breather (9) Diagnostic connector (10) Customer interface connector (wire harness recepticle) (11) Drop box connector | |
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| Illustration 4 | g01943281 |
Bottom view (41) Flex plate bolt circle (M12 bolts) (42) Engine starter ring gear (43) Mounting flange for SAE No. 1 J617 flywheel housing for 12 bolt iron and 24 bolt aluminum housings (44) Control line pressure (45) Ecology drain (46) Magnetic plug (47) Transmission oil filter cover (5 X 11 filter) | |
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| Illustration 5 | g01943282 |
Work mode (straight through) (48) Transmission output speed sensor (49) Drop box breather (50) Work mode output speed sensor (51) Test port (work mode disengage pressure) (52) Test port (work mode engage pressure) (53) Work mode fork position sensor (54) Work mode engage solenoid (55) Work mode disengage solenoid | |
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| Illustration 6 | g01945536 |
2WD Drop box (56) Rear wheel drive engage solenoid (57) Rear wheel drive disengage solenoid (58) Test port (rear wheel drive disengage pressure) (59) Test port (rear wheel drive engage pressure) (60) Rear wheel drive disconnect speed sensor (61) Lube pressure (62) Rear wheel drive fork position sensor | |
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| Illustration 7 | g01945539 |
4WD Drop box (63) Test port (front wheel drive engage pressure) (64) Test port (front wheel drive disengage pressure) (65) Test port (filter outlet pressure and drop box lube pressure) (66) Drop box mounting pad (67) Drop box oil filter (68) Front wheel drive disconnect speed sensor | |
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| Illustration 8 | g01945540 |
4WD Drop box (69) Front wheel drive disengage solenoid (70) Front wheel drive engage solenoid (71) Front wheel drive fork position sensor (72) Magnetic plug (73) Ecology drain (74) Drop box magnetic screen | |
TH35
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| Illustration 9 | g01943284 |
TH35 (75) Torque converter housing (76) PTO's SAE "B" J744 13 teeth splines (CW rotation, two and four bolt pump mounts), speed ratio 1:1 (77) Lifting eye (78) PTO's SAE "C" J744 14 teeth splines (CCW rotation, two and four bolt pump mounts), speed ratio 1:1 (79) Test port (torque converter lock up clutch) (80) Torque converter output speed sensor (81) Electronic control module (ECM) (82) Transmission output speed sensor (83) Diagnostic connector (84) Customer interface connector (wire harness receptacle) (85) Drop box connector (86) Output yoke (87) Test port (clutch 6 pressure) (88) Test port (clutch 5 pressure) (89) Test port (clutch 4 pressure) (90) Test port (clutch 3 pressure) (91) Test port (clutch 2 pressure) (92) Test port (clutch 1 pressure) (93) Test port (torque converter inlet pressure) (94) Relief valve (torque converter inlet pressure) (95) Torque converter inlet temperature sensor (96) Transmission oil filter cover (5 X 7 filter) (97) Test port (transmission supply pressure) (98) Filter bypass valve (99) Test port (transmission filter inlet pressure and scheduled oil sample "SOS" port "1") (100) Filter bypass switch (101) Lifting points (M22 thds) (102) Isolator mounting pad Ø 145 mm (Ø 5.71 inch) (103) Heavy duty mounting bracket (with isolators) for TH35-E81 ( 275-9383 Transmission Mounting Gp ) (104) Customer mounting bolt (M24 X 3 thds) (105) Transmission dry wall mounts (do not remove) (106) Test port (transmission lube pressure) (107) Oil inlet from cooler 27 mm (1.06 inch) (108) Torque converter outlet temperature sensor (109) Oil outlet to cooler 27 mm (1.06 inch) (110) Test port (converter out pressure port and scheduled oil sample "SOS" port "2") (111) Transmission filler tube and dipstick (112) Transmission identification plate (113) Magnetic pickup | |
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| Illustration 10 | g01943301 |
Rear view (114) Engine output speed sensor (115) Breather (83) Diagnostic connector (84) Customer interface connector (wire harness receptacle) (85) Drop box connector | |
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| Illustration 11 | g01943302 |
Bottom view (116) Flex plate bolt circle (M12 bolts) (117) Engine starter ring gear (118) Mounting flange for SAE No. 1 J617 flywheel housing for 12 bolt iron and 24 bolt aluminum housings (119) Control line pressure (120) Ecology drain (121) Magnetic plug (122) Transmission oil filter cover (5 x 11 filter) | |
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| Illustration 12 | g01943305 |
Work mode (straight through) (123) Transmission output speed sensor (124) Drop box breather (125) Work mode output speed sensor (126) Test port (work mode disengage pressure) (127) Test port (work mode engage pressure) (128) Work mode fork position sensor (129) Work mode engage solenoid (130) Work mode disengage solenoid | |
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| Illustration 13 | g01943306 |
2WD Drop box (131) Rear wheel drive engage solenoid (132) Rear wheel drive disengage solenoid (133) Test port (rear wheel drive disengage pressure) (134) Test port (rear wheel drive engage pressure) (135) Rear wheel drive disconnect speed sensor (136) Lube pressure (137) Rear wheel drive fork position sensor | |
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| Illustration 14 | g01943307 |
4WD Drop box (138) Test port (front wheel drive engage pressure) (139) Test port (front wheel drive disengage pressure) (140) Test port (filter outlet pressure and drop box lube pressure) (141) Drop box mounting pad (142) Drop box oil filter (143) Front wheel drive disconnect speed sensor | |
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| Illustration 15 | g01943837 |
4WD Drop box (144) Front wheel drive disengage solenoid (145) Front wheel drive engage solenoid (146) Front wheel drive fork position sensor (147) Magnetic plug (148) Ecology drain (149) Drop box magnetic screen | |
Drop box
The drop box is used in order to provide propulsion to the driveline of the vehicle. The drop box will drive the winches for the draw works. The drop box changes the mode of operation by engaging or by disengaging the disconnects. When the transmission is in road mode, the lower driveline of the drop box is coupled to the engine and the transmission. In this mode, the upper driveline is disengaged. When the transmission is in the work-over mode, the upper driveline of the drop box is coupled to the engine and the transmission. In this mode, the lower driveline is disengaged. Only one driveline may be engaged at any time. The bottom disconnects are used in order to connect to the machine driveline. The bottom rear disconnect is connected to the rear wheels. The bottom front disconnect is optional. The bottom front disconnect is used in order to enable the front wheel drive.
Note: The drop box is operated hydraulically so that when the top disconnect engage solenoid is energized the bottom disconnect disengage solenoid is energized and vice versa. This prevents a single short to the +battery fault from engaging a drive. Also, the dual transmission output speed sensors that are on the TH31 and TH35 have been moved. One transmission output speed is located on the gear group. The second sensor is located on the disconnect. The sensors send the required information to the Transmission ECU.
The engagement of each disconnect is controlled automatically by the ECU. The top disconnect is disengaged first in order to engage the bottom disconnect. The optional bottom front disconnect can only be engaged while the bottom rear disconnect is engaged.
The following must take place before the drop box will change modes.
- The transmission is in NEUTRAL.
- The output speed of the engine is below 800 RPM.
- The ground speed is 0.
- Three seconds has elapsed since the last request of a gear shift.
- A valid signal from the position sensors is received by the Transmission ECU.
Workover Mode
Note: The workover mode will not be allowed unless the Transmission ECU verifies the signal from the position sensor. When a valid signal is sent, the upper driveline will be engaged and the lower driveline will be disengaged. The upper disconnects can only be engaged from the rear deck.
If the workover mode is engaged and the position sensor fails, the drop box will remain in the workover mode. This mode is allowed until a change to the mode is requested. When the drop box sees the request, the drop box will place the transmission into NEUTRAL and the workover mode will not be allowed. If the workover mode is disengaged and the sensor fails, the transmission will lock in NEUTRAL.
Road Mode
The road mode will not be allowed unless the Transmission ECU verifies the signal from the position sensor. When a valid signal is sent, the lower driveline will be engaged and the upper driveline will be disengaged. The lower disconnects can only be engaged from the cab.
If the road mode is engaged and the position sensor fails, the drop box will remain in the road mode. This mode is allowed until a change to the mode is requested. When the drop box sees the request, the drop box will place the transmission into NEUTRAL and the road mode will not be allowed. If the road mode is disengaged and the sensor fails, the transmission will lock in NEUTRAL.