Commander 2WD V8-4.7L (2008)
The TCM monitors gear ratio changes by monitoring the Input and Output Speed Sensors. The Input, or Turbine Speed Sensor sends an electrical signal
to the TCM that represents input shaft rpm. The Output Speed Sensor provides the TCM with output shaft speed information.
By comparing the two inputs, the TCM can determine transmission gear position. This is important to the CVI calculation because the TCM determines
CVIs by monitoring how long it takes for a gear change to occur.
Gear ratios can be determined by using the Scan Tool and reading the Input/Output Speed Sensor values in the "Monitors" display. Gear ratio can be
obtained by dividing the Input Speed Sensor value by the Output Speed Sensor value.
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
volume of fluid need to apply the element increases.
Certain mechanical failures within the input clutch assembly can cause inadequate or out-of-range element volumes. Also, defective Input/Output Speed
Sensors and wiring can cause these conditions. The following chart identifies the appropriate clutch volumes and when they are monitored/updated:
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
following:
-
Shift lever position
-
Throttle position
-
Engine load
-
Fluid temperature
-
Software level
As driving conditions change, the TCM appropriately adjusts the shift schedule. Refer to the following chart to determine the appropriate operation
expected, depending on driving conditions.
