Mercedes-Benz first series automatic transmission


The Mercedes-Benz first series of automatic transmission was produced from 1961 to 1983 in four- and three-speed variants for Mercedes-Benz passenger cars. In addition, variants for commercial vehicles were offered.

Abstract

The Mercedes-Benz first series of automatic transmission started off in 1961 with the K4A 025 and was followed up by a family with a more reliable design. This started in 1964 with the K4B 050 and ended up in the K4C 025 and K4A 040 as the four-speed automatic transmissions.
Later, when the torque converter technique was fully established, the W3A 040 and W3B 050 were launched as three-speed derivates for V8 engines. At the same time the fluid coupling for the smaller engines was replaced by a torque converter as well, which leads to the W4A 025.
Beside this the version W4A 018 for vans and off road vehicles, and the W4A 035 for light trucks were derived.

Specifications

Introduction

This transmission was the first Mercedes-Benz automatic transmission in house developing. Before this, the company used semi automatic systems like a vacuum-powered shifting for overdrive or the "Hydrak" hydraulic automatic clutch system. Alternatively, they bought automatic transmissions of other vendors, such as BorgWarner.
The automatic transmissions are for engines with longitudinal layout for rear-wheel-drive layout passenger cars. The control of the fully automatic system is fully hydraulic and it uses electrical wire only for the kickdown solenoid valve and the neutral safety switch. Three-speed units use two planetary gearsets and 4-speed units use three planetary gearsets.
Physically, it can be recognized for its pan which uses sixteen bolts.

Basic concept

For the 4-speed models 8 main components are used. The 3-speed-models uses 7 main components, which shows economic equivalence with the direct competitor.

Gear ratios

Models

K4A 025

The K4A 025 is the first of the series, launched in April 1961 for the W111 220SEB, later replaced with the K4C 025. It is a 4-speed unit and uses fluid coupling. It is the only exemption which uses only two planetary gearsets for four speeds.

K4B 050

The layout of the K4A 025 turned out as not very reliable. The Mercedes-Benz 600 from 1964, the first post-war "Grand Mercedes", is powered by the Mercedes-Benz M100 engine. The automatic transmission was replaced by a three planetary gearset design to handle the much higher torque of the big block V8 engine and to meet the much higher standards of luxury vehicles.

K4C 025 and K4A 040

The K4C 025 was the core model of the first automatic transmission series from Mercedes-Benz. The layout is based on the K4B 050, which turned out as much more reliable as the previous layout from the K4A 025. With the small block V8 engine M 116 the K4A 040 as a stronger version of the same design was launched.

W3A 040 and W3B 050

As a three-speed unit, the W3A 040 and W3B 050 is combined with V8 engines, and it uses torque converter instead of fluid coupling. The transmission saves one planetary gearset and uses the same housing as the four-speed versions. The free space therefore is used to reinforce the shift elements to handle the higher torque of the V8 engines.
First the W3A 040 was released for the all new M117 V8 engine of the Mercedes-Benz W108 and W109 in 1971. The second in the series is the W3B 050, which was released initially for the W116 450 SE and SEL in 1973. At that time the four-speed transmission for the 350 SE and SEL was replaced by this three-speed model. The reinforced W3B 050 reinforced is the strongest of the series, able to handle the input of the enlarged version of the Mercedes-Benz M100 engine, the biggest Mercedes-Benz engine in post-war history, exclusively used in the W116 450 SEL 6.9.

W4B 025

The W4B 025 is the K4C 025, where the fluid-coupling is replaced by a torque converter. Used in L4, L5 and L6 engines due to its lower torque output. For V8-engines see W3A 040 and W3B 050 above.
In normal situations, it rests statioary in 2nd gear, but it will use 1st gear when the vehicle starts moving and throttle is applied or if L position is selected in gear selector.

W4A 018 and W4B 035

The W4A 018 was derived from the W4B 025 for vans up to 5.600 kg and off road vehicles, the W4B 035 from the W4B 025 and K4A 040 for light trucks up to 13.000 kg. The main difference is the use of straight toothed planetary gearsets instead of helical toothed ones for better fuel efficiency at the price of lower noise comfort.

Applications

K4C 025

K4A 040

W109 and W108----
Chassis codeCar modelEngine codeTransmission codeNotes
109.057300 SEL 3.53.5 L M 116 V8722.201worldwide except USA
108.067280 SE 3.53.5 L M 116 V8722.201worldwide except USA
108.068280 SEL 3.53.5 L M 116 V8722.201worldwide except USA

R107 and C107---
Chassis codeCar modelEngine codeTransmission code
107.043350 SL116.982, 116.984 722.201
107.023350 SLC116.982, 116.984 722.201

W3A 040

W109 and W108----
Chassis codeCar modelEngine codeTransmission codeNotes
109.056300 SEL 4.54.5 L M 117 V8722.000USA only
108.057280 SE 4.54.5 L M 117 V8722.000USA only
108.058280 SEL 4.54.5 L M 117 V8722.000USA only

R107 and C107----
Chassis codeCar modelEngine codeTransmission codeNotes
107.043350 SL116.982, 116.984 722.002-
107.023350 SLC116.982, 116.984 722.002-
107.044450 SL117.982, 117.985 722.004USA and Japan only
107.024450 SLC117.982, 117.985 722.004USA and Japan only

W3B 050

W116----
Chassis codeCar modelEngine codeTransmission codeNotes
116.032450 SE117.983, 117.986 722.001worldwide except USA and Japan
116.033450 SEL117.983, 117.986 722.001worldwide except USA and Japan
116.036450 SEL 6.9100.985722.003722.003 · W3B 050 reinforced

W4B 025

W114 and W115---
Chassis codeCar modelEngine codeTransmission code
114.015 and 114.615230.6180.954722.105
114.017 and 114.617230.6 Lang180.954722.105
114.011 and 114.611250130.923722.104
114.023 and 114.623250 C130.923722.104
114.060 and 114.660280110.921722.102
114.073 and 114.673280 C110.921722.102
114.062 and 114.662280 E110.981722.103
114.072 and 114.672280 CE110.981722.103
115.015 and 115.615200115.923722.106
115.017230.4115.951722.110
115.115 and 115.715200 D615.913722.107
115.110 and 115.710220 D615.912722.107
115.112220 D Lang615.912722.107
115.117240D616.916722.108
115.119240 D Lang616.916722.108
115.114240 D 3.0617.910722.109

W123----
Chassis codeCar modelEngine codeTransmission codeNotes
123.020200115.938, 115.939722.115-
123.220200102.920, 102.939722.121-
123.280200 T102.920, 102.939722.121-
123.023230115.954722.119-
123.083230 T115.954722.119-
123.043230 C115.954722.119-
123.223230 E102.980722.122-
123.283230 TE102.980722.122-
123.243230 CE102.980722.122-
123.026250123.920, 123.921722.113-
123.086250 T123.920, 123.921722.113-
123.028250 Lang123.920, 123.921722.113-
123.030280110.923722.111-
123.050280 C110.923722.111-
123.033280 E110.984, 110.988722.112-
123.093280 TE110.984, 110.988722.112-
123.053280 CE110.984, 110.988722.112-
123.120200 D615.940722.116-
123.126220 D615.941722.116-
123.123240 D616.912722.117-
123.183240 TD616.912722.117-
123.125240 D Lang616.912722.117-
123.130300 D617.912722.118-
123.190300 TD617.912722.118-
123.132300 D Lang617.912722.118-
123.150300 CD617.912722.118USA only