1. Copyright © 2003 General Motors Corporation.
All Rights Reserved.

2. Automatic Transmission
Welcome to
Allison LCT 1000
Automatic Transmission
Diagnostic Close-up
Course # D

3. The material contained in this course component was accurate and current at the time of course development.

4. Web Site

5. Question 1 In which of the following regions
is your dealership located?
A. Atlanta
B. Chicago
C. Dallas
D. Los Angeles
E. New York

6. Question 2
Which of the following best describes your experience level at GM dealerships?
A. Greater than 10 years
B. Between 5-10 years
C. Between 2-5 years
D. Less than 2 years

7. Course Goal
Apply concepts and procedures to diagnose an Allison LCT 1000 transmission.

8. Session Objectives
 Identify normal Allison LCT operational characteristics
 Identify hydraulic and electronic functions required for proper operation
 Choose appropriate diagnostic strategy based upon observation of operating parameters

10. Clutch Application Chart

15. Question 3
Which clutch is maintained by main pressure in steady state 4th gear and 5th gear?
A. C1
B. C2
C. C3
D. C5

17. Class 2 Data Line
PCM
TCM
CLASS 2

19. Factors Affecting Basic TCM Shift Control
Engine torque increases
Temperature changes

20. New/Reprogrammed TCM  Adaptive values set to base calibration
 Actual shift compared to an ideal shift
 TCM changes settings of adaptive values closer to ideal shift level

24. Question
Can you provide an explanation of the LCT 1000 shift adapt strategy?
Call in Now

27. Inputs Throttle angle via PCM NSBU switch (PNP)
Pressure Switch Assembly (PSA)
TFT sensor

29. Wiring Harness

31. Question
Which clutch has failed in the LCT 1000 and what caused the failure?
Call in Now

32. Question
What will the customer’s concern be with a failed C3 clutch?
Call in Now

33. Clutch Application Chart

34. DTC P1720/P0746 “A” Trim Solenoid (controlled clutch not engaged)
 Incorrect on-coming gear ratio
 Defaults back to previous range

36. Clutch Circuit Leak Clutch piston seals Barrel component seals
 Hydraulic passages in the case and case components
Valve body and components

37. Clutch Application Chart

38. Question
What is causing the C5 clutch to slip?
Call in Now

39. Hydraulic Default Test
Reverse: no gear
3rd Gear: no gear

40. Question
Based on the results of the hydraulic default test, what type of malfunction are we looking for, and what should be our next step?
Call in Now

41. Causes  Massive leak in the main circuit
 Pump damage: however, this will usually be accompanied by noise
 Something preventing the pump from priming and pressurizing fluid

44. J46409

46. DTCs
TCM: P0748

47. Question
What types of circuit faults are we looking for with this DTC?
Call in Now

48. “A” Trim Solenoid Commanded
0% Duty Cycle Displayed

51. Test Results
60º C (140º F)
“A” Trim Solenoid = 7

52. Question 4
Using the resistance versus temperature chart and the results of testing, what do the results indicate?
A. High resistance in the circuit
B. Low resistance in the circuit
C. The solenoid windings are open
D. The resistance is within specifications

53. Question
If the resistance was too high, where would you check for the high resistance and what would you be looking for?
Call in Now

56. Question 5
If CKT 1786 was shorted to ground what type of fault would you look for?
A. PCM DTC stored
B. TCM DTC stored
C. Inoperative PRNDL
D. Incorrect engine operation

57. RANGE RANGE RANGE RANGE
TCM
RANGE RANGE RANGE RANGE
A B C P

59. Diagnostic Scenario  Erratic shifting
 Sometimes the transmission shifts to what seems to be an inappropriate gear
 Sometimes the transmission shifts to neutral
 MIL on

61. DTC P1711 Diagnostics  “E” Switch Circuit: OK
 Valve Body Inspection: Not Yet, per updated diagnostics

63. Question 6
On a transmission that is operating correctly, which forward gear should be produced when the C connector is removed?
A. 1st gear
B. 2nd gear
C. 3rd gear
D. 5th gear

65. Session Summary
 Identify Allison LCT 1000 and operational characteristics
 Identify electronic controls and functions
 Describe strategic diagnostic path to servicing Allison LCT 1000
 Identify diagnostic procedures and service procedures

66. Post-test Question 1 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
Which of the following clutches is used to hold the P3 ring gear stationary?
A. C1
B. C2
C. C4
D. C5

67. Post-test Question 2 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
Which clutch could be malfunctioning if a truck is missing 4th and 5th gear?
A. C1
B. C2
C. C4
D. C5

68. Post-test Question 3 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
When an Allison transmission is replaced, the TCM should be ______.
A. replaced
B. reset to base calibrations
C. reprogrammed to the “slow” adapts
D. re-learned to the PCM

69. Post-test Question 4 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
“VCM/Trans” listed on the Tech 2 Message Monitor identifies _____.
A. the TCM has stopped communicating
B. the TCM has a DTC
C. the PCM class 2 data line is open
D. the TCM is operating correctly

70. Post-test Question 5 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
What will the shift adapt display if the TCM is still making large adjustments for a particular shift?
A. Slow
B. Fast
C. Converged
D. It will flash

71. Post-test Question 6 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
When removing the TCM C1 connector, the transmission should provide which hydraulic default gears?
A. 1st and 3rd
B. Reverse and 5th
C. 3rd and 5th
D. Reverse and 3rd

72. Post-test Question 7 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
During a clutch test, the pressure drops and stays low and the turbine speed sensor increases and stays high. What does this indicate?
A. A hydraulic leak
B. An electrical fault
C. A damaged stator
D. Normal operation

73. Post-test Question 8 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
If you suspect that an Allison transmission is leaking, you should _________.
A. replace the transmission
B. replace the cooler lines
C. add UV dye and leak check
D. perform clutch test

74. Post-test Question 9 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
Which NSBU circuit fault could cause an 8.1L engine to not exceed 3000 RPM and cause harsh shifts?
A. CKT #1786 shorted to ground
B. CKT #1786 open
C. TCM power supply shorted to ground
D. TCM power supply open

75. Post-test Question 10 20 21 19 17 16 22 18 24 28 29 27 26 15 25 23 14 4 5 3 2 1 6 7 12 13 11 10 8 9 30 31 52 53 51 50 48 49 54 55 59 60 58 57 56 47 46 37 38 36 35 33 34 32 39 44 45 40 43 42 41
During a clutch test, in certain ranges the pressure drops and returns to normal and the turbine speed sensor increases and stays high. What does this indicate?
A. A hydraulic leak
B. An electrical fault
C. A slipping clutch
D. Normal operation

76. Evaluation Instructions
Turn to evaluation module; remove and complete evaluation
Use keypad to answer questions
Press the “Next Quest” key after each question
Press “Yes” when completed

77. Evaluation Instructions cont. Evaluation Instructions
Fill out back of evaluation form
Include today’s date, time and time zone
Fax to the Detroit IDL Center at (586)

78. Automatic Transmission
Thank you for attending
Allison LCT 1000
Automatic Transmission
Diagnostic Close-up
Course # D

79. Copyright © 2003 General Motors Corporation.
All Rights Reserved.