Clutch Volume Indexes; Clutch Volumes And Clearances - ATSG Chrysler 45RFE Service Manual

CLUTCH VOLUME INDEXES

An important function of the TCM is to monitor Clutch Volume Indexes (CVI). CVIs represent the volume of
fluid needed to compress a clutch pack properly.
The TCM monitors gear ratio changes by monitoring the Input and Output Speed Sensors. The Input Speed
Sensor sends an AC voltage signal to the TCM that represents input shaft rpm. The Output Speed Sensor
provides the TCM with output shaft speed information.
By comparing these two inputs, the TCM can determine actual gear ratio. 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 DRB 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.
For example, if the input shaft is turning at 1000 rpm and the output shaft is turning at 500 rpm, the TCM can
determine that the gear ratio is 2:1. In 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 a 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 the
adaptive controls. As friction material wears, the volume of fluid needed to apply the friction element increases.
Certain mechanical problems within the transmission assembly such as broken return springs, out of position
snap rings, excessive clutch pack clearance, or improper assembly can cause inadequate or out-of-range CVI
readings. Also defective Input/Output Speed Sensors, wiring and poor connections may cause these same
conditions. The following chart identifies the proper CVIs, when they are monitored and updated and the
proper clutch pack clearances.
CLUTCH
Low/Reverse
2nd Clutch
Overdrive
4th Clutch
Underdrive
Reverse
10
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Technical Service Information

CLUTCH VOLUMES AND CLEARANCES

WHEN UPDATED
2-1 or 3-1 Downshift
3-2 Kickdown shift
2-3 Upshift
3-4 Upshift
4-3 Kickdown shift
Not Monitored
AUTOMATIC TRANSMISSION SERVICE GROUP
PROPER VOLUME
82 to 134
25 to 64
30 to 64
30 to 64
44 to 92
Not Monitored
Figure 6
CLUTCH CLEARANCE
1.14-1.91mm (.045"-.075")
0.53-1.27mm (.021"-.050")
1.01-1.65mm (.040"-.065")
0.81-1.35mm (.032"-.053")
0.76-1.60mm (.030"-.063")
0.81-1.24mm (.032"-.049")
Copyright © 1999 ATSG