TRANSMISSION CONTROL MODULE (Auto)
TCM - Main Operations
TCM - Main Operations
Lets look at how our Automatic Transmission in the Challenger and its TCM operate and how its described in Chrysler/Dodge documentation.
Here are some general highlights of our automatic transmission:
The NAG1 (5-Speed) Automatic Transmission
The NAG1 automatic transmission is an electronically controlled 5-speed transmission
with a lock-up clutch in the torque converter. The ratios for the gear stages are obtained
by 3 planetary gear sets. Fifth gear is designed as an overdrive with a high-speed ratio.
NAG1 identifies a family of transmissions and means New Automatic Gearbox, generation 1.
Various marketing names are associated with the NAG1 family of transmissions, depending
on the transmission variation being used in a specific vehicle. Some examples of the marketing
names are: W5A300, W5A380, and W5A580. The marketing name can be interpreted as follows:
1. W = A transmission using a hydraulic torque converter.
2. 5 = 5 forward gears.
3. A = Automatic Transmission.
4. 580 = Maximum input torque capacity in Newton meters.
The gears are actuated electronically/hydraulically. The gears are shifted by means of an
appropriate combination of three multi-disc holding clutches, three multi-disc driving
clutches, and two freewheeling clutches.
Electronic transmission control enables precise adaptation of pressures to the respective
operating conditions and to the engine output during the shift phase which results in a
significant improvement in shift quality.
The transmission control is divided into the electronic and hydraulic transmission control
functions. While the electronic transmission control is responsible for gear selection and
for matching the pressures to the torque to be transmitted, the transmission's power supply
control occurs via hydraulic elements in the electrohydraulic control module. The oil supply
to the hydraulic elements, such as the hydrodynamic torque converter, the shift elements
and the hydraulic transmission control, is provided by way of an oil pump connected with
the torque converter.
The Transmission Control Module (TCM) allows for the precise adaptation of pressures
to the corresponding operating conditions and to the engine output during the gearshift phase,
resulting in a noticeable improvement in shift quality. The engine speed limit can be reached
in the individual gears at full throttle and kickdown. The shift range can be changed in the
forward gears while driving, but the TCM employs a downshift safeguard to prevent
over-revving the engine. The system offers the additional advantage of flexible adaptation
to different vehicle and engine variants.
EMERGENCY RUNNING FUNCTION
In order to ensure a safe driving state and to prevent damage to the automatic transmission,
the TCM control module switches to limp-home mode in the event of critical faults.
A diagnostic trouble code (DTC) assigned to the fault is stored in memory. All solenoid
and regulating valves are thus de-energized.
The net effect is:
1. The last engaged gear remains engaged.
2. The modulating pressure and shift pressures rise to the maximum levels.
3. The torque converter lockup clutch is deactivated.
In order to preserve the operability of the vehicle to some extent, the hydraulic control
can be used to engage 2nd gear or reverse using the following procedure:
1. Stop the vehicle.
2. Move selector lever to "P".
3. Switch off engine.
4. Wait at least 10 seconds. Start engine.
5. Move selector lever to D: 2nd gear.
6. Move selector lever to R: Reverse gear.
The limp-home function remains active until the DTC is rectified or the stored DTC is erased
with the appropriate scan tool. Sporadic faults can be reset via ignition OFF/ON.
TCM ADAPTATION - NAG1 Only
The adaptation procedure requires the use of the appropriate scan tool. This program allows
the electronic transmission system to re-calibrate itself. This will provide the proper baseline
transmission operation. The adaptation procedure should be performed if any of the following
procedures are performed:
1. Transmission Assembly Replacement
2. Transmission Control Module Replacement
3. Clutch Plate and/or Seal Replacement
4. Electro-hydraulic Unit Replacement or Recondition
1. With the scan tool, reset the Transmission adaptives.
Resetting the adaptives will set the adaptives to factory settings.
For Upshift adaptation, the Transmission temperature must be greater than 60°C (140°F)
and less than 100°C (212°F). Failure to stay within these temperature ranges will void this
2. Drive the vehicle until the transmission temperature is in the specified range.
3. Perform 4 to 5 coast downs from 5th to 4th gear and then 4th to 3rd gear.
4. From a stop, moderately accelerate the vehicle and obtain all forward gear ranges while keeping
the Engine RPM below 1800 RPM. Repeat this procedure 4 to 5 times.
5. Obtaining 5th gear may be difficult at 1800 RPM. Allow transmission to shift into 5th gear at a higher RPM then lower the RPM to 1800 and perform manual shifts between 4th and 5th gears using the shift lever.
6. The TCM will store the adaptives every 10 minutes. After completion of the adaptation procedure make sure the vehicle stays running for at least 10 minutes.
7. It is possible to manually store the adaptives under the 10 minute time frame using the scan tool Store Adaptives procedure.
TRANSMISSION CONTROL MODULE - NAG1
The TCM is located under the left side of the instrument panel for left hand drive vehicles.
The electronic control system consists of various components providing inputs to the
transmission control module (TCM). The TCM monitors transmission sensors, shift lever
position, and bus messages to determine transmission shift strategy. After shift strategies
are determined, the TCM controls the actuation of transmission solenoids, which controls
the routing of hydraulic fluid within the transmission, by moving a sequence of four valves
to make a shift occur.
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