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AUTOMATIC - NAG1 SERVICE INFORMATION
TRANSMISSION IDENTIFICATION
The transmission name, NAG1, means New Automatic Gearbox, generation 1.
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
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 (4). A coated intermediate plate provides the sealing. The oil
pump (2) and the outer multi-disc carrier of the multi-disc holding clutch, B1 (4), are bolted to the converter housing.
The stator shaft (19) is pressed into it and prevented from rotating by splines. The electrohydraulic control unit (16)
is bolted to the transmission housing from underneath. A sheet metal steel oil pan forms the closure.
MECHANICAL SECTION
The mechanical section consists of a driveshaft (3), output shaft (10), a sun gear shaft, and three planetary gear
sets (14, 15 and 17) 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 (20) and driving clutch K2 (6) is supplied through
bores in the drive shaft (3). The oil pressure to driving clutch K3 (8) is transmitted through the output shaft (10). 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 lubricating oil. The parking lock gear (11) is connected to
the output shaft (10) via splines.
Freewheel F1 (18) and F2 (13) are used to optimize the shifts. The front freewheel, F1 (18), is supported on the
extension of the stator shaft (19) on the transmission side and, in the locking direction, connects the sun gear of the
front planetary gear set (17) to the transmission housing. In the locking direction, the rear freewheel, F2 (13), con-
nects the sun gear of the center planetary gear set (15) to the sun gear of the rear planetary gear set (14).
ELECTROHYDRAULIC CONTROL UNIT
The electrohydraulic control unit (16) 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 (4) and K1 (5) clutches. The 2-3
shift group controls the K2 (6) and K3 (8) clutches. The 3-4 shift group controls the K3 (8) and B2 (9) clutches.
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