The Mercedes-Benz first series of automatic transmission was produced from 1961 to 1983 in two 4-speed designs, at Mercedes-Benz later referred to as 1st and 2nd automatic transmission generation, and a 3-speed variant of the second design for passenger cars. In addition, transmissions with the second 4-speed design were offered for commercial vehicles until the mid-1990s.

All these designs are for cars with a longitudinal engine, rear-wheel-drive layout. 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.

Physically, it can be recognized for its pan which uses 16 bolts.

Key data

+ Gear ratios ModelDesign Type FirstDeliv-ery Gear Total Span Avg.Step Components Nomenclature R 1 2 3 4 Nomi-nal Effec-tive Cen-ter Total perGear Cou-pling GearsCount Ver-sion Maximum Input Torque K4A 0251st w/o1st 1961Johannes Looman · Gear Transmissions · pp. 133 ff · 2 Gearsets3 Brakes3 Clutches K 4 A K4B 0502nd w/o2nd 1964 3 Gearsets3Brakes2Clutches K 4 B K4C 025K4A 040W4B 0252nd 722.2722.2722.12nd 196719691972 KKW · p. 10 4 CAB W4A 0182nd 720.12nd 1975 W 4 A W4B 0352nd TBD 1975 W 4 B W3A 040W3A 050W3A 050reinf.2nd 720.0722.0722.02nd 197119731975 2 Gearsets3 Brakes2 Clutches W 3 A

History

The K4A 025 was the first Mercedes automatic transmission developed in-house. 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 the Detroit gear 3-speed automatic transmission from BorgWarner for the 300 c and 300 d (not to be confused with the later 300 D and its successors).

1st generation 1961: K4A 025— first 4-speed design with 2 planetary gearsets —

Specifications

The K4A 025 is the first design, launched in April 1961 for the W 111 220 SEb, later replaced with the more reliable second design K4C 025 (type 722.2). It is a 4-speed unit and uses fluid coupling (also referred in some manuals as hydraulic/automatic clutch).

This first design did not work out. It results in poor shifting comfort, which does not meet Mercedes-Benz standards. This applies in particular to the change from 2nd to 3rd gear (and vice versa), which requires a group change—that is, all four of the relevant shift levers must be released or actuated.

Planetary gearset concept first design

For this 1st automatic transmission generation 8 main components are used. It is the only exemption which uses only 2 planetary gearsets for 4 speeds.

2nd generation 1964: K4B 050 and follow-up products— second 4-speed design with 3 planetary gearsets —

Specifications

The Mercedes-Benz 600, which was unveiled in September 1963 at the International Motor Show in Frankfurt, went into production in September 1964 and was the first post-war "Grand Mercedes", powered by the Mercedes-Benz M100 engine. This made a gearbox for the highest demands of luxury vehicles necessary.

The 1st automatic transmission generation was out of the question from the start. The introduction of the 600 was therefore taken as an opportunity to develop a completely new design for the automatic transmission, at Mercedes-Benz later referred to as 2nd automatic transmission generation.

Mercedes-Benz licensed a variant – featuring cross-coupled ring gears and carriers instead of coupled sun gears – of the Simpson planetary gearset in order to replace the original epicyclic gearset of the first design and thereby eliminate the need for group changes.

Models

1964: K4B 050

The first model with the new design was the K4B 050. Beside the new layout the number of pinions is doubled from 3 to 6 to handle the much higher torque of the big block V8 engine M 100.

1967: K4C 025

After the satisfactory experience with the new design, it was adopted with slightly different gear ratios in 1967 for the new core model K4C 025 (Type 722.2) of the 2nd automatic transmission generation from Mercedes-Benz.

1969: K4A 040

With the introduction of the small block V8 engine M 116, the K4A 040 (Type 722.2) was launched, which is a reinforced version of the K4C 025 with the same gear ratios to accommodate the increased torque.

1972: W4B 025

When the torque converter technique was fully established, the fluid coupling was replaced by a torque converter for the smaller engines, which leads to the W4B 025 (type 722.1). Used in L4, L5 and L6 engines due to its lower torque output. In normal situations, it rests stationary in 2nd gear, but it will use 1st gear when the vehicle starts moving and throttle is applied p. 11 or if L position is selected in gear selector.

Variants for commercial vehicles

The W4A 018 (type 720.1) was derived from the W4B 025 (type 722.1) for light-duty trucks and vans up to and off-road vehicles. The W4B 035 is based on the same design and designated for medium-duty trucks up to . The main difference is the use of straight-cut planetary gearsets instead of helical-cut ones for better fuel efficiency at the price of lower noise comfort.

Planetary gearset concept second design

For this 2nd generation 4-speed variants 8 main components are used.

2nd generation 1971: W3A 040 and follow-up products— 3-speed variant of the second design with 2 planetary gearsets —

Specifications

When the torque converter technique was fully established, 3-speed variants, the W3A 040 and W3B 050 (type 722.0) are combined with V8 engines, using torque converters instead of fluid couplings. The transmission design saves 1 planetary gearset, so the Simpson planetary gearset is no longer necessary. Therefore this variant is not based on a Simpson gearset design, but on the Detroit Gear. Since the same housing as in the 4-speed versions is used, the free space therefore is used to reinforce the shift elements (brakes and clutches) to handle the higher torque of the V8 engines.

First the W3A 040 was released for the all new M117 V8 engine of the W 108 and W 109 in 1971.

The second variant in the series is the W3B 050, which was released initially for the W 116 450 SE/SEL in 1973. At that time the 4-speed transmission for the 350 SE/SEL was replaced by this 3-speed variant.

The reinforced W3B 050 reinforced (type 722.003) is the strongest variant of the series, able to handle the input of the enlarged version of the M 100, the biggest Mercedes-Benz engine in post-war history,Only surpassed by the Mercedes-Benz 770, built from 1930 to 1943 exclusively used in the W 116 450 SEL 6.9.

The W3B 050 was available as an optional extra for the Porsche 928 from 1977 to 1984.

Planetary gearset concept second design, 3-speed variant

For the 3-speed variants 7 main components are used, which shows economic equivalence with the direct competitor.

Applications

+ Variants and applications Model Car Model Chassis code Car model Enginecode Transmissioncode Notes K4A 025 (1st generation) E-Class 1961–1968 W 110 S-Class 1961–1965 (saloon) W 111 1961–1968 (coupé/convertible) W 111 1961–1965 (saloon) W 112 1962–1968 (coupé/convertible) W 112 1965–1968 W 108 1965–1968 W 109 SL-Class 1963–1971 W 113 K4B 050 (2nd generation) S-Class 1964–1981 600 (W 100) 1968–1972 300 SEL 6.3 (W 109) K4C 025 (Type 722.2, 2nd generation) E-Class 114.015 230.6 180.954 722.203 114.017 230.6 Lang 114.011 250 130.923 722.204 114.023 250 C 114.060 280 110.921 722.202 114.073 280 C 114.062 280 E 110.981 722.200 114.072 280 CE 115.015 200 115.923 722.205 115.010 220 115.920 115.115 200 D 615.913 722.206 115.110 220 D 615.912 115.112 220 D Lang S-Class 1968–1971 (coupé/convertible) W 111 1968–1972 W 108 1968–1972 W 109 K4A 040 (Type 722.2, 2nd generation) S-Class 109.056 300 SEL 3.5 116.981 (D-Jet) 722.201 worldwideexcept USA 108.057 280 SE 3.5 116.980 (D-Jet) 108.058 280 SEL 3.5 SL-Class 107.043 350 SL 116.982 (D-Jet)116.984 (K-Jet) 722.201 107.023 350 SLC W3A 040 (Type 722.0, 2nd generation) S-Class 109.057 300 SEL 4.5 117.981 (D-Jet) 722.000 USA only 108.067 280 SE 4.5 117.984 (D-Jet) 108.068 280 SEL 4.5 S-Class 116.028 350 SE 116.983 (D-Jet)116.985 (K-Jet) 722.002 116.029 350 SEL 116.032 450 SE 117.983 (D-Jet)117.986 (K-Jet) 722.004 USA andJapan only 116.033 450 SEL SL-Class 107.043 350 SL 116.982 (D-Jet)116.984 (K-Jet) 722.002 107.023 350 SLC 107.044 450 SL 117.982 (D-Jet)117.985 (K-Jet) 722.004 USA andJapan only 107.024 450 SLC W3B 050 (Type 722.0, 2nd generation) S-Class 116.032 450 SE 117.983 (D-Jet)117.986 (K-Jet) 722.001 worldwide exceptUSA and Japan 116.033 450 SEL 116.036 450 SEL 6.9 100.985 (K-Jet) 722.003W3B 050 SL-Class 107.044 450 SL 117.982 (D-Jet)117.985 (K-Jet) 722.001 worldwide exceptUSA and Japan 107.024 450 SLC 107.026 450 SLC 5.0 117.960 (K-Jet) Porsche 1977 – 1984 928 W4B 025 (Type 722.1, 2nd generation) E-Class 114.615 230.6 180.954 722.105 114.617 230.6 Lang 114.611 250 130.923 722.104 114.623 250 C 114.660 280 110.921 722.102 114.673 280 C 114.662 280 E 110.981 722.103 114.672 280 CE 115.615 200 115.923 722.106 115.017 230.4 115.951 722.110 115.715 200 D 615.913 722.107 115.710 220 D 615.912 115.117 240 D 616.916 722.108 115.119 240 D Lang 115.114 240 D 3.0 617.910 722.109 E-Class 123.020 200 115.938115.939 722.115 123.220 200 102.920102.939 722.121 123.280 200 T 123.023 230 115.954 722.119 123.083 230 T 123.043 230 C 123.223 230 E 102.980 722.122 123.283 230 TE 123.243 230 CE 123.026 250 123.920123.921 722.113 123.086 250 T 123.028 250 Lang 123.030 280 110.923 722.111 123.050 280 C 123.033 280 E 110.984110.988 722.112 123.093 280 TE 123.053 280 CE 123.120 200 D 615.940 722.116 123.126 220 D 615.941 123.123 240 D 616.912 722.117 123.183 240 TD 123.125 240 D Lang 123.130 300 D 617.912 722.118 123.190 300 TD 123.132 300 D Lang 123.150 300 CD USA only S-Class 116.020 280 S 110.922 722.100722.102722.111 116.024 280 SE 110.983 (D-Jet)110.985 (K-Jet) 722.101722.103722.112 116.025 280 SEL 116.120 300 SD 617.950 722.120 USA only SL-Class 107.042 280 SL 110.982 (D-Jet)110.986 (K-Jet) 722.103722.112 107.022 280 SLC

See also

List of Mercedes-Benz transmissions

Notes

References