Mercedes-Benz first series automatic transmission

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Mercedes-Benz K4A 025

K4B 050 · K4C 025 · K4A 040 W3A 040 · W3B 050 · W4B 025

W4A 018 · W4B 035
Overview
ManufacturerDaimler AG
Production1961–1983
Body and chassis
Class3 and 4-speed longitudinal automatic transmission
Chronology
Successor4G-Tronic

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.

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 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.

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

1961: K4A 025
— 4-Speed Transmission With 2 Planetary Gearsets —
[edit]

Layout[edit]

The K4A 025[a] (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[edit]

For this first four-speed model[b] eight main components[c] are used. It is the only exemption which uses only two planetary gearsets for four speeds.

Gear Teeth and Ratios[d] Planetary Gearset
Teeth Simple[e]
Count Total Avg.
Model
Type
Version
First Delivery
[f]
[g]
[h]
[i]
Brakes
Clutches
Ratio
Span
Gear
Step
Gear R 1 2 3 4
Step
–R : 1 1 : 2 2 : 3 3 : 4
K4A 025
N/A
25 kp⋅m (181 lb⋅ft)
1961[2][3]
50
76
44
76
3
3
3.9789 1.5846
Ratio
−4.1455
3.9789
2.5200
1.5789
1.0000
Step 1.0418 1.5789 1.5960 1.5789
Ratio
  1. ^ Kupplungs-4-Gang-Automatik bis 25 kpm Eingangsdrehmoment
    (clutch-4-gear-automatic with 25 kp⋅m (181 lb⋅ft) maximum input torque
  2. ^ plus 1 reverse gear
  3. ^ 2 simple planetary gearsets, 3 brakes, 3 clutches
  4. ^ Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage
  5. ^ Layout
    (1) Planetary gearset 1 is on the input (turbine) side
    (2) Output shaft is carrier 2 (the planetary gear carrier of gearset 2)
  6. ^ Sun gear of gearset 1
  7. ^ Ring gear of gearset 1
  8. ^ Sun gear of gearset 2
  9. ^ Ring gear of gearset 2

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

Layout[edit]

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 three to six 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).[4] 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[5] 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 5,600 kg (12,350 lb) 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 13,000 kg (28,660 lb).[6] The main difference is the use of straight toothed planetary gearsets instead of skew toothed ones for better fuel efficiency at the price of lower noise comfort.

Specifications[edit]

For this second four-speed models[a] eight main components[b] are used.[4]

Gear Teeth and Ratios[c] Planetary Gearset
Teeth Simple[d]
Count Total Avg.
Simpson Simple
Model
Type
Version
First Delivery
[e]
[f]
[g]
[h]
[i]
[j]
Brakes
Clutches
Ratio
Span
Gear
Step
Gear R 1 2 3 4
Step
–R : 1 1 : 2 2 : 3 3 : 4
K4B 050
N/A
51 kp⋅m (369 lb⋅ft)
1964
50
76
44
76
44
76
3
2
3.9789 1.5846
Ratio
−4.1455
3.9789
2.4589
1.5789
1.0000
Step 1.0418 1.6182 1.5573 1.5789
K4C 025
722.2
25 kp⋅m (181 lb⋅ft)
1967[7]
44
76
44
76
35
76
3
2
3.9833 1.5852
Ratio
−5.4779
3.9833
2.3855
1.4605
1.0000
Step 1.3752 1.6698 1.6333 1.4605
K4A 040
722.2
40 kp⋅m (289 lb⋅ft)
1969
44
76
44
76
35
76
3
2
3.9833 1.5852
Ratio −5.4779 3.9833 2.3855 1.4605 1.0000
Step 1.3752 1.6698 1.6333 1.4605
W4B 025
722.1
25 kp⋅m (181 lb⋅ft)
1972[7]
44
76
44
76
35
76
3
2
3.9833 1.5852
Ratio −5.4779 3.9833 2.3855 1.4605 1.0000
Step 1.3752 1.6698 1.6333 1.4605
W4A 018[k]
720.1
18 kp⋅m (130 lb⋅ft)
1975
46
80
46
80
37
80
3
2
4.0060 1.5882
Ratio
−5.4994
4.0060
2.3911
1.4625
1.0000
Step 1.3728 1.6754 1.6349 1.4625
W4B 035[l]
N/A
35 kp⋅m (253 lb⋅ft)
1975
42
78
42
78
36
78
3
2
4.1758 1.6103
Ratio
−5.8810
4.1758
2.4115
1.4615
1.0000
Step 1.4083 1.7316 1.6500 1.4615
Ratio
R & Even
Ratio
Odd
  1. ^ plus 1 reverse gear
  2. ^ 3 simple planetary gearsets, 3 brakes, 2 clutches
  3. ^ Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage
  4. ^ Layout
    (1) Planetary gearset 1 is on the input (turbine) side
    (2) Output shaft is carrier 3 (the planetary gear carrier of gearset 3)
  5. ^ Sun gear of gearset 1
  6. ^ Ring gear of gearset 1
  7. ^ Sun gear of gearset 2
  8. ^ Ring gear of gearset 2
  9. ^ Sun gear of gearset 3
  10. ^ Ring gear of gearset 3
  11. ^ for light duty trucks up to 5,600 kg (12,350 lb)[8][6]
  12. ^ for medium duty trucks up to 13,000 kg (28,660 lb)[6][9]

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

Layout[edit]

When the torque converter technique was fully established, three-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][4] 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 (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 four-speed transmission for the 350 SE and SEL was replaced by this three-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,[10] exclusively used in the W116 450 SEL 6.9.

Specifications[edit]

For the three-speed models[a] seven main components[b] are used, which shows economic equivalence with the direct competitor.

Gear Teeth and Ratios[c] Planetary Gearset
Teeth Simple[d]
Count Total Avg.
Model
Type
Version
First Delivery
[e]
[f]
[g]
[h]
Brakes
Clutches
Ratio
Span
Gear
Step
Gear R 1 2 3
Step
–R : 1 1 : 2 2 : 3
W3A 040
722.0
40 kp⋅m (289 lb⋅ft)
1971[11]
44
76
35
76
3
2
2.3061 1.5186
Ratio
−1.8361
2.3061
1.4605
1.0000
Step 0.7962 1.5789 1.4605
W3B 050
722.0
50 kp⋅m (362 lb⋅ft)
1973[11]
44
76
35
76
3
2
2.3061 1.5186
Ratio −1.8361 2.3061 1.4605 1.0000
Step 0.7962 1.5789 1.4605
W3B 050 reinf.
722.0
56 kp⋅m (405 lb⋅ft)
1975[11]
44
76
35
76
3
2
2.3061 1.5186
Ratio −1.8361 2.3061 1.4605 1.0000
Step 0.7962 1.5789 1.4605
Ratio
  1. ^ plus 1 reverse gear
  2. ^ 2 simple planetary gearsets,[4] 3 brakes, 2 clutches
  3. ^ Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage
  4. ^ Layout
    (1) Planetary gearset 1 is on the input (turbine) side
    (2) Output shaft is carrier 2 (the planetary gear carrier of gearset 2)
  5. ^ Sun gear of gearset 1
  6. ^ Ring gear of gearset 1
  7. ^ Sun gear of gearset 2
  8. ^ Ring gear of gearset 2

Applications[edit]

K4C 025[edit]

K4A 040[edit]

W3A 040[edit]

W3B 050[edit]

W4B 025[edit]

See also[edit]

References[edit]

  1. ^ a b "50 years of automatic transmissions from Mercedes-Benz".
  2. ^ Johannes Looman · Zahnradgetriebe · pp. 133 ff · Berlin and Heidelberg 1970 · Print ISBN 978-3-540-04894-7
  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. ^ a b c d "MB Passenger Car Series 116, PDF p. 10" (PDF).
  5. ^ "MB Passenger Car Series 116, PDF p. 11" (PDF).
  6. ^ a b c 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. ^ a b 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
  8. ^ Hans Joachim Foerster · Automatische Fahrzeuggetriebe · p. 487 · Berlin and Heidelberg 1991 · Print ISBN 978-3-642-84119-4 · Online ISBN 978-3-642-84118-7
  9. ^ Hans Joachim Foerster · Automatische Fahrzeuggetriebe · p. 489 · Berlin and Heidelberg 1991 · Print ISBN 978-3-642-84119-4 · Online ISBN 978-3-642-84118-7
  10. ^ Only surpassed by the Mercedes-Benz 770, built from 1930 to 1943
  11. ^ a b c Hans Joachim Foerster · Automatische Fahrzeuggetriebe · p. 452 · Berlin and Heidelberg 1991 · Print ISBN 978-3-642-84119-4 · Online ISBN 978-3-642-84118-7
  12. ^ "MB AUS 1979, PDF p. 57" (PDF).