Table of Contents
Advertisement
VA
TRANSMISSION CONTROL MODULE (Continued)
• Low and High ATF Temperature.
Upshift
1-2
To:
Activated
1-2/4-5
By
Solenoid:
Shift
17.8
Point (at
km/h
35.2% of
(11.6
throttle)
mph)
Downshift
5-4
From:
Activated
1-2/4-5
By
Solenoid:
Shift
55.7
Point
km/h
(34.61
mph)
DOWNSHIFT SAFETY
Selector lever downshifts are not performed if inad-
missible high engine rpm is sensed.
ADAPTATION
To equalize tolerances and wear, an automatic
adaptation takes place for:
• Shift Time.
• Clutch Filling Time.
• Clutch Filling Pressure.
• Torque Converter Lock-Up Control.
Adaptation data may be stored permanently and to
some extent, can be diagnosed.
Driving Style Adaptation
The shift point is modified in steps based on the
information from the inputs. The control module
looks at inputs such as:
• vehicle acceleration and deceleration (calculated
by the TCM).
• rate of change as well as the position of the
throttle pedal (fuel injection information from the
ECM).
• lateral acceleration (calculated by the TCM).
• gear change frequency (how often the shift
occurs).
Based on how aggressive the driver is, the TCM
moves up the shift so that the present gear is held a
little longer before the next upshift. If the driving
style is still aggressive, the shift point is modified up
to ten steps. If the driving returns to normal, then
2-3
3-4
4-5
2-3
3-4
1-2/4-5
32.1
67.5
73.8
km/h
km/h
km/h
(19.95
(41.94
(45.86
mph)
mph)
mph)
4-3
3-2
2-1
3-4
2-3
1-2/4-5
40.5
24.4
15.1
km/h
km/h
km/h
(25.17
(15.16
(9.38
mph)
mph)
mph)
ELECTRONIC CONTROL MODULES 8E - 7
the shift point modification also returns to the base
position.
This adaptation has no memory. The adaptation to
driving style is nothing more than a shift point mod-
ification meant to assist an aggressive driver. The
shift points are adjusted for the moment and return
to base position as soon as the inputs are controlled
in a more rational manner.
Shift Time Adaptation (Shift Overlap Adaptation, Working
Pressure)
Shift time adaptation is the ability of the TCM to
electronically alter the time it takes to go from one
gear to another. Shift time is defined as the time it
takes to disengage one shift member while another is
being applied. Shift time adaptation is divided into
four categories:
33. Accelerating upshift, which is an upshift under
a load. For shift time adaptation for the 1-2 upshift
to take place, the transmission must shift from 1st to
2nd in six different engine load ranges vs. transmis-
sion output speed ranges.
34. Decelerating upshift, which is an upshift under
no load. This shift is a rolling upshift and is accom-
plished by letting the vehicle roll into the next gear.
35. Accelerating downshift, which is a downshift
under load. This shift can be initiated by the throttle,
with or without kickdown. The shift selector can also
be used.
36. Decelerating downshift, which is accomplished
by coasting down. As the speed of the vehicle
decreases, the transmission downshifts.
Fill Pressure Adaptation (Apply Pressure Adaptation,
Modulating Pressure)
Fill pressure adaptation is the ability of the TCM
to modify the pressure used to engage a shift mem-
ber. The value of this pressure determines how firm
the shift will be.
• If too much pressure is used, the shift will be
hard.
• If too little pressure is used, the transmission
may slip.
The pressure adjustment is needed to compensate
for the tolerances of the shift pressure solenoid valve.
The amount the solenoid valve opens as well as how
quickly the valve can move, has an effect on the pres-
sure. The return spring for the shift member pro-
vides a resistance that must be overcome by the
pressure in order for shift member to apply. These
return springs have slightly different values. This
also affects the application pressure and is compen-
sated for by fill pressure adaptation.
Fill Time Adaptation (Engagement Time Adaptation)
Fill time is the time it takes to fill the piston cav-
ity and take up any clearances for a friction element
Advertisement
Table of Contents
