2:1. In direct drive (3rd gear), the gear ratio changes
to 1:1. The gear ratio changes as clutches are applied
and released. By monitoring the length of time it
takes for the gear ratio to change following a shift
request, the TCM can determine the volume of fluid
used to apply or release a friction element.
The volume of transmission fluid needed to apply
the friction elements are continuously updated for
adaptive controls. As friction material wears, the vol-
ume of fluid need to apply the element increases.
Certain mechanical problems within the input
clutch assembly (broken return springs, out of posi-
tion snap rings, excessive clutch pack clearance,
improper assembly, etc.) can cause inadequate or out-
of-range element volumes. Also, defective Input/Out-
put Speed Sensors and wiring can cause these
conditions. The following chart identifies the appro-
priate clutch volumes and when they are monitored/
updated:
CLUTCH VOLUMES
Clutch
When Updated
Proper Clutch
Volume
Shift Sequence Oil Temperature Throttle Angle
L/R
2-1 or 3-1 coast
downshift
>70° <5° 35to83
2/4 1-2 shift
> 110°
5 - 54°
20 to 77
OD 2-3 shift 48 to 150
UD 4-3 or 4-2 shift > 5° 24 to 70
SHIFT SCHEDULES
As mentioned earlier, the TCM has programming
that allows it to select a variety of shift schedules.
Shift schedule selection is dependent on the follow-
ing:
• Shift lever position
• Throttle position
• Engine load
• Fluid temperature
• Software level
As driving conditions change, the TCM appropri-
ately adjusts the shift schedule. Refer to the follow-
ing chart to determine the appropriate operation
expected, depending on driving conditions.
Fig. 15 Example of CVI Calculation
1 – OUTPUT SPEED SENSOR
2 – OUTPUT SHAFT
3 – CLUTCH PACK
4 – SEPARATOR PLATE
5 – FRICTION DISCS
6 – INPUT SHAFT
7 – INPUT SPEED SENSOR
8 – PISTON AND SEAL
21 - 12 42LE TRANSAXLE LH
DESCRIPTION AND OPERATION (Continued)
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