mercedes mechanic




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 “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 vehicles and engines. Basically, the automatic transmission with electronic control offers the following advantages:

Reduces fuel consumption.
Improved shift comfort.
More favorable step-up through the five gears.
Increased service life and reliability.
Lower maintenance costs.


    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. 

    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

      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 transmission housing from underneath. A sheet metal steel oil pan forms the closure.

      The mechanical section consists of an 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 lubricating 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.