Mercedes-Benz first series automatic transmission explained

Mercedes-Benz K4A 025K4B 050 · K4C 025 · K4A 040W3A 040 · W3B 050 · W4B 025W4A 018 · W4B 035
Production:	1961–1983
Manufacturer:	Daimler AG
Class:	3 and 4-speed longitudinal automatic transmission
Successor:	4G-Tronic

The Mercedes-Benz first series of automatic transmission was produced from 1961 to 1983 in 4- and 3-speed variants for Mercedes-Benz passenger cars. In addition, variants for commercial vehicles were offered.

This transmission was the first Mercedes-Benz automatic transmission in-house developing.^[1] 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).

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.

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

Gear Ratios!!R!1!2!3!4!Total
Span!Span
Center!Avg.
Step!Compo-
nents

K4A 025 · 1961									2 Gearsets 3 Brakes 3 Clutches
K4B 050 · 1964									3 Gearsets 3 Brakes 2 Clutches
K4C 025 · 1967 K4A 040 · 1969 W4B 025 · 1972
W4A 018 · 1975
W4B 035 · 1975
W3A 040 · 1971 W3A 050 · 1973 W3A 050 reinf. · 1975									2 Gearsets 3 Brakes 2 Clutches

1961: K4A 025
- 4-Speed Transmission With 2 Planetary Gearsets  -

Layout

The K4A 025 (without type designation) is the first of the series, launched in April 1961 for the W111 220 SEb, later replaced with the more reliable K4C 025 (type 722.2). It is a 4-speed unit and uses fluid coupling (also referred in some manuals as hydraulic/automatic clutch).

The design of the transmission 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, i.e. affects all shift elements.

Specifications

For this first 4-speed model 8 main components are used. It is the only exemption which uses only 2 planetary gearsets for 4 speeds.

With Assessment!colspan=2

Planetary Gearset: Teeth Simple	Count	Total Center	Avg.
Model Type	Version First Delivery	S1 R1	S2 R2	Brakes Clutches	Ratio Span	Gear Step
Gear Ratio		R {i _{R}}	1 {i _{1}}	2 {i _{2}}	3 {i _{3}}	4 {i _{4}}
Step		- \tfrac{i _{R}} {i _{1}}	\tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{2}}	\tfrac{i _{2}} {i _{3}}	\tfrac{i _{3}} {i _{4}}
Δ Step				\tfrac{i _{1}} {i _{2}} : \tfrac{i _{2}} {i _{3}}	\tfrac{i _{2}} {i _{3}} : \tfrac{i _{3}} {i _{4}}
Shaft Speed		\tfrac{i _{1}} {i _{R}}	\tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{2}}	\tfrac{i _{1}} {i _{3}}	\tfrac{i _{1}} {i _{4}}
Δ Shaft Speed		0 - \tfrac{i _{1}} {i _{R}}	\tfrac{i _{1}} {i _{1}} - 0	\tfrac{i _{1}} {i _{2}} - \tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{3}} - \tfrac{i _{1}} {i _{2}}	\tfrac{i _{1}} {i _{4}} - \tfrac{i _{1}} {i _{3}}
K4A 025 N/A	25kpm 1961^[2] ^[3]	50 76	44 76	3 3
Gear Ratio		- \tfrac{ 228 }{ 55 }	\tfrac{ 378 }{ 95 }			1.0000 \tfrac{ 1 }{ 1 }
Step		1.0418	1.0000			1.5789
Δ Step					1.0108
Speed		-0.9598	1.0000	1.5789	2.5200	3.9789
Δ Speed		0.9598	1.0000	0.5789	0.9411	1.4589
Ratio R & Even		- \tfrac{R _{1} (S _{2+} R _{2)}} {S _{1} S _{2}}	\tfrac{S _{1+} R _{1}} {S _{1}}		\tfrac{ 1 } { 1 }
Ratio Odd			\tfrac{(S _{1+} R _{1)} (S _{2+} R _{2)}} {S _{1} R _{2}}		\tfrac{S _{2+} R _{2}{R} _{2}}
Algebra And Actuated Shift Elements
Brake A			❶	❶
Brake B			❶		❶
Brake R		❶
Clutch D					❶	❶
Clutch E		❶
Clutch F				❶		❶

1964: K4B 050 And Follow-Up Products
- 4-Speed Transmissions With 3 Planetary Gearsets  -

Layout

The Mercedes-Benz 600 from April 1964, the first post-war "Grand Mercedes", is powered by the Mercedes-Benz M100 engine.This made a gearbox for the highest demands of luxury vehicles necessary. The design of the gearbox in the range was out of the question from the outset. The introduction of the 600 was therefore taken as an opportunity to develop a completely new design for the automatic transmission.

The first model with this new layout was the K4B 050 (without type designation). 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.

After the satisfactory experience with the new design, it was adopted in 1967 for the new core model K4C 025 (Type 722.2) of the first automatic transmission series from Mercedes-Benz. With the small block V8 engine M 116, the K4A 040 (Type 722.2) was launched as a more powerful version of the same design.

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^[4] or if L position is selected in gear selector.

The W4A 018 (type 720.1) was derived from the W4B 025 (type 722.1) for vans up to 5600kg (12,300lb)^[5] and off road vehicles, the W4B 035 from the W4B 025 (type 722.1) and K4A 040 (type 722.2) for light trucks up to 13000kg (29,000lb).^[6] 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.

Specifications

For this second 4-speed models 8 main components are used.^[7]

With Assessment!colspan=3

Planetary Gearset: Teeth	Count	Total Center	Avg.
Simpson				Simple
Model Type	Version First Delivery	S1 R1	S2 R2	S3 R3	Brakes Clutches	Ratio Span	Gear Step
Gear Ratio		R {i _{R}}		1 {i _{1}}	2 {i _{2}}	3 {i _{3}}	4 {i _{4}}
Step		- \tfrac{i _{R}} {i _{1}}		\tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{2}}	\tfrac{i _{2}} {i _{3}}	\tfrac{i _{3}} {i _{4}}
Δ Step					\tfrac{i _{1}} {i _{2}} : \tfrac{i _{2}} {i _{3}}	\tfrac{i _{2}} {i _{3}} : \tfrac{i _{3}} {i _{4}}
Shaft Speed		\tfrac{i _{1}} {i _{R}}		\tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{2}}	\tfrac{i _{1}} {i _{3}}	\tfrac{i _{1}} {i _{4}}
Δ Shaft Speed		0 - \tfrac{i _{1}} {i _{R}}		\tfrac{i _{1}} {i _{1}} - 0	\tfrac{i _{1}} {i _{2}} - \tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{3}} - \tfrac{i _{1}} {i _{2}}	\tfrac{i _{1}} {i _{4}} - \tfrac{i _{1}} {i _{3}}
K4B 050 N/A	51kpm 1964	50 76	44 76	44 76	3 2
Gear Ratio		- \tfrac{ 228 }{ 55 }		\tfrac{ 378 }{ 95 }	\tfrac{ 1 , 168 }{ 475 }		1.0000 \tfrac{ 1 }{ 1 }
Step		1.0418		1.0000	1.6182		1.5789
Δ Step					1.0391
Speed		-0.9598		1.0000	1.6182	2.5200	3.9789
Δ Speed		0.9598		1.0000	0.6182	0.9018	1.4589
K4C 025 722.2	25kpm 1967	44 76	44 76	35 76	3 2
Gear Ratio				\tfrac{ 1 , 665 }{ 418 }			1.0000 \tfrac{ 1 }{ 1 }
Step				1.0000			1.4605
Δ Step						1.1183
Speed				1.0000	1.6696	2.7273	3.9833
Δ Speed				1.0000	0.6696	1.0575	1.2560
K4A 040 722.2	40kpm 1969	44 76	44 76	35 76	3 2
Ratio							1.0000
W4B 025 722.1	25kpm 1972	44 76	44 76	35 76	3 2
Ratio							1.0000
W4A 018 720.1	18kpm 1975	46 80	46 80	37 80	3 2
Gear Ratio				\tfrac{ 7 , 371 }{ 1840 }			1.0000 \tfrac{ 1 }{ 1 }
Step				1.0000			1.4625
Δ Step						1.1179
Speed				1.0000	1.6754	2.7391	4.0060
Δ Speed				1.0000	0.6754	1.0637	1.2668
W4B 035 N/A	35kpm 1975	42 78	42 78	36 78	3 2
Gear Ratio				\tfrac{ 3 , 420 }{ 819 }			1.0000 \tfrac{ 1 }{ 1 }
Step				1.0000			1.4615
Δ Step						1.1289
Speed				1.0000	1.7316	2.8571	4.1758
Δ Speed				1.0000	0.7316	1.1255	1.3187
Ratio R & Even		- \tfrac{R _{1} (S _{3+} R _{3)}} {S _{1} S _{3}}		\tfrac{(S _{1} (S _{2+} R _{2)+} R _{1} S _{2)} (S _{3+} R _{3)}} {S _{1} (S _{2+} R _{2)} R _{3}}			\tfrac{ 1 } { 1 }
Ratio Odd			i _{1} = \tfrac{(S _{1+} R _{1)} (S _{3+} R _{3)}} {S _{1} R _{3}}			i _{3} = \tfrac{S _{3+} R _{3}} {R _{3}}
Algebra And Actuated Shift Elements
Brake A					❶
Brake B				❶	❶	❶
Brake R		❶
Clutch D						❶	❶
Clutch E		❶		❶			❶

1971: W3A 040 And Follow-Up Products
- 3-Speed Transmissions With 2 Planetary Gearsets  -

Layout

When the torque converter technique was fully established, 3-speed units, the W3A 040 and W3B 050 (type 722.0) is combined with V8 engines, and it uses torque converter instead of fluid coupling.^{[1] [7]} The transmission saves 1 planetary gearset and uses the same housing as the 4-speed versions. 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 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 4-speed transmission for the 350 SE and SEL was replaced by this 3-speed model. The reinforced W3B 050 reinforced (type 722.003) 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,^[8] exclusively used in the W116 450 SEL 6.9.

Specifications

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

With Assessment!colspan=2

Simple Planetary Gearset: Teeth	Count	Total Center	Avg.
Model Type	Version First Delivery	S1 R1	S2 R2	Brakes Clutches	Ratio Span	Gear Step
Gear Ratio		R {i _{R}}		1 {i _{1}}	2 {i _{2}}	3 {i _{3}}
Step		- \tfrac{i _{R}} {i _{1}}		\tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{2}}	\tfrac{i _{2}} {i _{3}}
Δ Step					\tfrac{i _{1}} {i _{2}} : \tfrac{i _{2}} {i _{3}}
Shaft Speed		\tfrac{i _{1}} {i _{R}}		\tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{2}}	\tfrac{i _{1}} {i _{3}}
Δ Shaft Speed		0 - \tfrac{i _{1}} {i _{R}}		\tfrac{i _{1}} {i _{1}} - 0	\tfrac{i _{1}} {i _{2}} - \tfrac{i _{1}} {i _{1}}	\tfrac{i _{1}} {i _{3}} - \tfrac{i _{1}} {i _{2}}
W4A 040 722.0	40kpm 1971^[9]	44 76	35 76	3 2
Gear Ratio				\tfrac{ 1 , 665 }{ 722 }	\tfrac{ 63 }{ 25 }	1.0000 \tfrac{ 1 }{ 1 }
Step				1.0000	1.5789	1.4605
Δ Step					1.0811
Speed				1.0000	1.5789	2.3061
Δ Speed				1.0000	0.5789	0.9411
W4A 050 722.0	50kpm 1973	44 76	35 76	3 2
Ratio						1.0000
W4A 050 reinf. 722.0	56kpm 1975	44 76	35 76	3 2
Ratio						1.0000
Ratio	- \tfrac{S _{1} (S _{2+} R _{2)}} {R _{1} S _{2}}		\tfrac{(S _{1+} R _{1)} (S _{2+} R _{2)}} {R _{1} R _{2}}		\tfrac{S _{2+} R _{2}} {R _{2}}	\tfrac{ 1 } { 1 }
Algebra And Actuated Shift Elements
Brake A				❶
Brake B				❶	❶
Brake R		❶
Clutch D					❶	❶
Clutch E		❶				❶

Applications

K4C 025

W114 and W115!Chassis code!Car model!Engine code!Transmission
code

114.015 and 114.615	230.6	180.954	722.203
114.017 and 114.617	230.6 Lang
114.011 and 114.611	250	130.923	722.204
114.023 and 114.623	250 C
114.060 and 114.660	280	110.921	722.202
114.073 and 114.673	280 C
114.062 and 114.662	280 E	110.981	722.200
114.072 and 114.672	280 CE
115.015 and 115.615	200	115.923	722.205
115.010	220	115.920
115.115 and 115.715	200 D	615.913	722.206
115.110 and 115.710	220 D	615.912
115.112	220 D Lang

K4A 040

W109 and W108!Chassis code!Car model!Engine code!Transmission
code!Notes

109.057	300 SEL 3.5	3.5 L M 116 V8	722.201	worldwide except USA
108.067	280 SE 3.5
108.068	280 SEL 3.5

R107 and C107!Chassis code!Car model!Engine code!Transmission
code

107.043	350 SL	116.982 (D-Jet) 116.984 (K-Jet)	722.201
107.023	350 SLC

W3A 040

W109 and W108!Chassis code!Car model!Engine code!Transmission
code!Notes

109.056	300 SEL 4.5	4.5 L M 117 V8	722.000	USA only
108.057	280 SE 4.5
108.058	280 SEL 4.5

R107 and C107!Chassis code!Car model!Engine code!Transmission
code!Notes

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 and Japan only
107.024	450 SLC

W116

Chassis code	Car model	Engine code	Transmission code	Notes
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 and Japan only
116.033	450 SEL

W3B 050

R107 and C107!Chassis code!Car model!Engine code!Transmission
code!Notes

107.044	450 SL	117.982 (D-Jet) 117.985 (K-Jet)	722.004	worldwide except USA and Japan
107.024	450 SLC

W116!Chassis code!Car model!Engine code!Transmission
code!Notes

116.032	450 SE	117.983 (D-Jet) 117.986 (K-Jet)	722.001	worldwide except USA and Japan
116.033	450 SEL
116.036	450 SEL 6.9	100.985	722.003	722.003 W3B 050 reinforced^[10]

W4B 025

R107 and C107!Chassis code!Car model!Engine code!Transmission
code

107.042	280 SL	110.982 110.986 110.990	722.103 722.112
107.022	280 SLC	110.982 110.986

W114 and W115!Chassis code!Car model!Engine code!Transmission
code

114.015 and 114.615	230.6	180.954	722.105
114.017 and 114.617	230.6 Lang
114.011 and 114.611	250	130.923	722.104
114.023 and 114.623	250 C
114.060 and 114.660	280	110.921	722.102
114.073 and 114.673	280 C
114.062 and 114.662	280 E	110.981	722.103
114.072 and 114.672	280 CE
115.015 and 115.615	200	115.923	722.106
115.017	230.4	115.951	722.110
115.115 and 115.715	200 D	615.913	722.107
115.110 and 115.710	220 D	615.912
115.112	220 D Lang
115.117	240 D	616.916	722.108
115.119	240 D Lang
115.114	240 D 3.0	617.910	722.109

W116!Chassis code!Car model!Engine code!Transmission
code!Notes

116.020	280 S	110.922	722.100 722.102 722.111
116.024	280 SE	110.983 (D-Jet) 110.985 (K-Jet)	722.101 722.103 722.112
116.025	280 SEL
116.120	300 SD	617.950	722.120	USA only

W123!Chassis code!Car model!Engine code!Transmission
code!Notes

123.020	200	115.938 115.939	722.115
123.220	200	102.920 102.939	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	123.920 123.921	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	110.984 110.988	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

See also

• List of Daimler AG transmissions

Notes and References

1. Web site: 50 years of automatic transmissions from Mercedes-Benz.
2. Johannes Looman · Zahnradgetriebe · pp. 133 ff · Berlin and Heidelberg 1970 · Print
3. Ergebnis und Ausblick · Festschrift für Herrn Prof. Dr. Hans Joachim Förster zum Ausscheiden als Direktor aus dem aktiven Dienst der Daimler-Benz AG November 1982 (Result And Outlook · commemorative publication for Prof. Dr. Hans Joachim Foerster on the occasion of leaving as director from active duty at Daimler-Benz AG November 1982) · pp. 6 · 20
4. Web site: MB Passenger Car Series 116, PDF p. 11.
5. Ergebnis und Ausblick · Festschrift für Herrn Prof. Dr. Hans Joachim Förster zum Ausscheiden als Direktor aus dem aktiven Dienst der Daimler-Benz AG November 1982 (Result And Outlook · commemorative publication for Prof. Dr. Hans Joachim Foerster on the occasion of leaving as director from active duty at Daimler-Benz AG November 1982) · pp. 7 · 20
6. Ergebnis und Ausblick · Festschrift für Herrn Prof. Dr. Hans Joachim Förster zum Ausscheiden als Direktor aus dem aktiven Dienst der Daimler-Benz AG November 1982 (Result And Outlook · commemorative publication for Prof. Dr. Hans Joachim Foerster on the occasion of leaving as director from active duty at Daimler-Benz AG November 1982) · pp. 9 · 22
7. Web site: MB Passenger Car Series 116, PDF p. 10.
8. Only surpassed by the Mercedes-Benz 770, built from 1930 to 1943
9. Hans Joachim Foerster · Automatische Fahrzeuggetriebe · p. 452 · Berlin and Heidelberg 1991 · Print · Online
10. Web site: MB AUS 1979, PDF p. 57.