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 Automatic Transmission

1 - TORQUE CONVERTER

11 - PARKING LOCK GEAR

2 - OIL PUMP

12 - INTERMEDIATE SHAFT

3 - DRIVESHAFT

13 - FREEWHEEL F2

4 - MULTI-DISC HOLDING CLUTCH B1

14 - REAR PLANETARY GEAR SET

5 - DRIVING CLUTCH K1

15 - CENTER PLANETARY GEAR SET

6 - DRIVING CLUTCH K2

16 - ELECTROHYDRAULIC CONTROL UNIT

7 - MULTI-DISC HOLDING CLUTCH B3

17 - FRONT PLANETARY GEAR SET

8 - DRIVING CLUTCH K3

18 - FREEWHEEL F1

9 - MULTI-DISC HOLDING CLUTCH B2

19 - STATOR SHAFT

10 - OUTPUT SHAFT

20 - TORQUE CONVERTER LOCK-UP CLUTCH

AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION

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NAG1 identifies a family of transmissions and means “N”ew “A”utomatic “G”earbox, generation 1. Various marketing
names are associated with the NAG1 family of transmissions, depending on the transmisson 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:

•

W = A transmission using a hydraulic torque converter.

•

5 = 5 forward gears.

•

A = Automatic Transmission.

•

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.

Furthermore, it offers the advantage of a flexible adaptation to various vehicle and engines.

Basically, the automatic transmission with electronic control offers the following advantages:

•

Reduces fuel consumption.

•

Improved shift comfort.

•

More favourable step-up through the five gears.

•

Increased service life and reliability.

•

Lower maintenance costs.

TRANSMISSION IDENTIFICATION

The transmission can be generically identified visually by the presence of a round 13-way connector located near
the front corner of the transmission oil pan, on the right side. Specific transmission information can be found
stamped into a pad on the left side of the transmission, above the oil pan rail.

TRANSMISSION GEAR RATIOS

The gear ratios for the NAG1 automatic transmission are as follows:

1st Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.59:1
2nd Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.19:1
3rd Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.41:1
4th Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.00:1
5th Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.83:1
Reverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.16:1
Reverse (In 4WD low Range) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.93:1

TRANSMISSION HOUSING

The converter housing and transmission are made from a light alloy. These are bolted together and centered via the
outer multi-disc carrier of multi-disc holding clutch, B1. A coated intermediate plate provides the sealing. The oil
pump and the outer multi-disc carrier of the multi-disc holding clutch, B1, are bolted to the converter housing. The
stator shaft is pressed into it and prevented from rotating by splines. The electrohydraulic unit is bolted to the trans-
mission housing from underneath. A sheet metal steel oil pan forms the closure.

MECHANICAL SECTION

The mechanical section consists of a input shaft, output shaft, a sun gear shaft, and three planetary gear sets which
are coupled to each other. The planetary gear sets each have four planetary pinion gears. The oil pressure for the
torque converter lock-up clutch and clutch K2 is supplied through bores in the input shaft. The oil pressure to clutch
K3 is transmitted through the output shaft. The lubricating oil is distributed through additional bores in both shafts.
All the bearing points of the gear sets, as well as the freewheeling clutches and actuators, are supplied with lubri-
cating oil. The parking lock gear is connected to the output shaft via splines.

Freewheeling clutches F1 and F2 are used to optimize the shifts. The front freewheel, F1, is supported on the
extension of the stator shaft on the transmission side and, in the locking direction, connects the sun gear of the front
planetary gear set to the transmission housing. In the locking direction, the rear freewheeling clutch, F2, connects
the sun gear of the center planetary gear set to the sun gear of the rear planetary gear set.

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AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION

ELECTROHYDRAULIC CONTROL UNIT

The electrohydraulic control unit comprises the shift plate made from light alloy for the hydraulic control and an
electrical control unit. The electrical control unit comprises of a supporting body made of plastic, into which the
electrical components are assembled. The supporting body is mounted on the shift plate and screwed to it.

Strip conductors inserted into the supporting body make the connection between the electrical components and a
plug connector. The connection to the wiring harness on the vehicle and the transmission control module (TCM) is
produced via this 13-pin plug connector with a bayonet lock.

SHIFT GROUPS

The hydraulic control components (including actuators) which are responsible for the pressure distribution before,
during, and after a gear change are described as a shift group. Each shift group contains a command valve, a
holding pressure shift valve, a shift pressure shift valve, overlap regulating valve, and a solenoid.

The hydraulic system contains three shift groups: 1-2/4-5, 2-3, and 3-4. Each shift group can also be described as
being in one of two possible states. The active shift group is described as being in the shift phase when it is actively
engaging/disengaging a clutch combination. The 1-2/4-5 shift group control the B1 and K1 clutches. The 2-3 shift
group controls the K2 and K3 clutches. The 3-4 shift group controls the K3 and B2 clutches.

OPERATION

The transmission control is divided into the electronic and hydraulic transmission control functions. While the elec-
tronic transmission control is responsible for gear selection and for matching the pressures to the torque to be trans-
mitted, 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 oper-
ating 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 mod-
ule switches to limp-home mode in the event of critical faults. A DTC assigned to the fault is stored in memory. All
solenoid and regulating valves are thus de-energized.

The net effect is:

•

The last engaged gear remains engaged.

•

The modulating pressure and shift pressures rise to the maximum levels.

•

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:

•

Stop the vehicle.

•

Move selector lever to

•

Switch off engine.

•

Wait at least 10 seconds.

•

Start engine.

•

Move selector lever to D: 2nd gear.

•

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 DRB

tool.

Sporadic faults can be reset via ignition OFF/ON.

CLUTCH APPLICATION

Refer to CLUTCH APPLICATION for which shift elements are applied in each gear position.

AUTOMATIC TRANSMISSION - NAG1 - SERVICE INFORMATION

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