Mercedes-Benz 4G-Tronic transmission is the unofficial name given to the transmission by car enthusiasts. At Mercedes-Benz referred to as 3rd automatic transmission generation, it was produced from 1979 to 1996 in 4-speed variants W4A 040, W4A 028 (both type 722.3), W4A 020 (type 722.4), and from 1990 on in a 5-speed variant W5A 030 (type 722.5).

Key data

+ Gear ratios Model Type FirstDeliv-ery Gear Total Span Avg.Step Components Nomenclature R 1 2 3 4 5 Nomi-nal Effec-tive Cen-ter Total perGear Cou-pling GearsCount Ver-sion Maximum Input Torque W4A 040 I 722.3 1979 3 Gearsets3 Brakes2 Clutches W 4 A W4A 020 722.4 1982 W4A 040 II 722.3 1985 W4A 028 1990 W5A 030 722.5 1990 4 Gearsets4 Brakes3 Clutches W 5 A

History

The W4A 040 and the W4A 020 were used until mid-1996. The W4A 028 variant was used for off-road applications (RWD and 4X4). The W5A 030 is basically the same transmission with an additional electrically controlled 5th gear overdrive section attached to the main body in a separate housing; it was available as an extra charge option. All 4G-Tronics were succeeded by the more modern and economic 5G-Tronic (Type 722.6) transmission that features an integrated 5th gear overdrive ratio, torque converter lock-up and fully electronic control.

From 1984 to 1991, the W4A 040 was available as an optional extra for the Porsche 928.

Specifications

The 4G-Tronic transmission is a hydraulically operated 4-speed automatic without lock-up that replaced the similarly designed W3A 040, W3B 050, and W4B 025 family of automatic transmissions with the introduction of the W126 S-Class in 1979. In some models it is calibrated to move off in second gear to reduce "creeping" and provide a smoother ride, selecting 1st only if the selector is in "2" or in case of abrupt acceleration. Other calibrations have the transmission rest in 2nd gear and kick down to 1st as soon as the accelerator is touched but before the throttle is opened. In some V8 installations a small control unit activates the kick down solenoid when the brake pedal is released so that the car moves off in 1st gear. Other attributes of this transmission include a 2-3 shift delay when the engine is cold in order to speed up catalyst warm-up. 4th gear is a 1:1 ratio. Controls are all mechanical and pneumatic, except for the kickdown solenoid and 2-3 upshift delay solenoid on some models.

In some markets a W-S (Winter - Standard / Sport) switch was provided on the shifter. Activating S mode changes a linkage which effectively shortens the throttle pressure bowden cable. This causes later, higher RPM shifts and on some models a move off in 1st gear instead of 2nd. On V8 models a B (Brake) range is available on the shifter. This activates the kickdown solenoid, forcing the transmission to shift down to 1st sooner for increased engine braking. A hydraulically activated piston prevents shifting into Reverse when the car is moving forward.

Models from 1990 and earlier allow for push starting the engine. They are fitted with a secondary fluid pump, driven by the transmission output shaft. When the vehicle is rolling at 20 mph shifting from Neutral to the 2 range will couple power to the engine. The secondary pump and thus the push starting facility was eliminated for the 1991 model year.

It is considered by enthusiasts to be one of the most reliable transmissions ever built by Mercedes-Benz with some examples exceeding 300,000 miles of service.

Planetary gearset concept

W4A models: manufacturing complexity

"To simplify production, the front group is now formed by a Ravigneaux set, which is immediately followed by the second group. This largely eliminates the need for hollow shafts and other connecting bells, which are so commonly found in planetary gearboxes. Where possible, sheet metal or die-cast parts are used. Cost-intensive material machining is limited to the manufacture of gears, shafts, and bolts."

+ Planetary gearset concept: manufacturing complexity WithAssessment Output:GearRatios InnovationElasticityΔ Output : Δ Input Input: Main Components Total Gearsets Brakes Clutches W4ARef. Object Topic Δ Number Relative Δ Δ Output Δ Input W4AW4B 025 44 Progress 88 33 33 22 Δ Number 0 0 0 0 0 Relative Δ W4AZF 4HP 22 44 EarlyMarket Position 810 33 34 23 Δ Number 0 -2 0 -1 -1 Relative Δ W4AZF 4HP 18 44 LateMarket Position 87 32 32 23 Δ Number 0 1 1 1 -1 Relative Δ W4A3-Speed 43 HistoricalMarket Position 87 32 33 22 Δ Number 1 1 1 0 0 Relative Δ

W5A: manufacturing complexity

The need of 2 housings and 2 different controls turn out the W5A 030 as the least economically designed automatic transmission ever manufactured for passenger cars. Obviously a transition solution: the direct successor, launched in 1996, requires 9 main components, 1 housing and 1 control.

+ Planetary gearset concept: manufacturing complexity WithAssessment Output:GearRatios InnovationElasticityΔ Output : Δ Input Input: Main Components Total Gearsets Brakes Clutches W5ARef. Object Topic Δ Number Relative Δ Δ Output Δ Input W5AW4A 54 Progress 118 43 43 32 Δ Number 1 3 1 1 1 Relative Δ W5AZF 5HP 18 55 EarlyMarket Position 1110 43 43 34 Δ Number 0 1 1 1 -1 Relative Δ W5AZF 5HP 30 55 LateMarket Position 119 43 43 33 Δ Number 0 2 1 1 0 Relative Δ W5A3-Speed 53 HistoricalMarket Position 117 42 43 32 Δ Number 2 4 2 1 1 Relative Δ

Quality

The most obvious flaw of the gearset concept is the second gear, which is clearly too short, but this affected all Mercedes-Benz transmissions, especially automatic transmissions. "The manual transmission plays a key role in the positive impression made by the small V8 engine in the large S-Class sedan. It simply suits the sporty performance characteristics of the engine better than the automatic transmission, although there is still room for improvement in terms of gear ratios. 2nd gear in particular seems a little too short with a range of only 90 km/h."

After Hans-Joachim Foerster, the originator of this flawed gear ratio, left the company in 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 in November 1982 Mercedes-Benz began to address this problem. This led to the introduction of the W4A 040 II with modified gear ratios in 1985. With the 7G-Tronic transmission from 2003, they finally succeeded in completely resolving this issue.

+ Planetary gearset concept: gear ratio quality In-Depth AnalysisWith AssessmentAnd Torque RatioAnd Efficiency Calculation Planetary Gearset: Teeth Count Nomi-nalEffec-tive Cen-ter Ravigneaux Simple Avg. ModelType VersionFirst Delivery S1R1 S2R2 S3R3 S4R4 BrakesClutches RatioSpan GearStep Gear R 1 2 3 4 5 GearRatio Step Δ Step ShaftSpeed Δ ShaftSpeed TorqueRatio Efficiency W4A 040 I722.3 1979Mercedes 722.3 & 722.4 Technical Overview 3450 5078 3478 32 Gear R 1 2 3 4 5 GearRatio 1.0000 Step 1.0000 1.4359 Δ Step 1.1700 Speed 1.0000 1.5238 2.5600 3.6759 Δ Speed 1.0000 0.5238 1.0362 1.1159 TorqueRatio –4.9659–4.8805 3.60913.5758 2.36872.3471 1.42721.4228 1.0000 Efficiency 0.96640.9497 0.98180.9728 0.98190.9730 0.99390.9909 1.0000 W4A 020722.4 1982 2642 4278 3878 32 Gear R 1 2 3 4 5 GearRatio 1.0000 Step 1.0000 1.6190 1.4872 Δ Step 1.0900 1.0887 Speed 1.0000 1.7647 2.8571 4.2491 Δ Speed 1.0000 0.7647 1.0924 1.3919 TorqueRatio –5.4811–5.3882 4.16644.1253 2.36472.3434 1.47741.4726 1.0000 Efficiency 0.96680.9504 0.98050.9709 0.98210.9733 0.99340.9902 1.0000 W4A 040 II722.3 19851988 2646 4678 3478 32 Gear R 1 2 3 4 5 GearRatio 1.0000 W4A 028722.3 1990 2646 4678 3478 32 Gear R 1 2 3 4 5 GearRatio 1.0000 W5A 030722.5 1990 2646 4678 3478 2678 43 Gear R 1 2 3 4 5 GearRatio 1.0000 Step 1.0000 1.5652 1.4359 1.3333 Δ Step 1.1003 1.0901 1.0769 Speed 1.0000 1.7222 2.6957 3.8707 5.1609 Δ Speed 1.0000 0.7222 0.9734 1.1750 1.2902 TorqueRatio –5.3977–5.3049 3.79883.7631 2.20982.1911 1.42721.4228 1.0000 0.74620.7442 Efficiency 0.96640.9497 0.98140.9722 0.98320.9749 0.99390.9909 1.0000 0.99490.9923 Actuated shift elements Brake A ❶ Brake B ❶ ❶ ❶ Brake R ❶ Brake S ❶ Clutch E ❶ ❶ ❶ Clutch F ❶ ❶ ❶ ❶ Clutch S ❶ ❶ ❶ ❶ ❶ Geometric ratios: speed conversion GearRatioR & 3OrdinaryElementaryNoted GearRatio1 & 4OrdinaryElementaryNoted GearRatio2 & 5OrdinaryElementaryNoted Kinetic ratios: torque conversion SpecificTorqueR & 3 SpecificTorque1 & 4 SpecificTorque2 & 5

Applications

+ Variants and applications Model Car Model Chassis code Car model Enginecode Transmissioncode Notes W4A 040 I+II (Type 722.3) C-Class 1985–1993 W 201 1993–1996 W 202 E-Class 123.026 250 123.920123.921 722.308 123.086 250 T 123.028 250 Lang 123.033 280 E 110.984110.988 722.300722.309 123.093 280 TE 722.309 123.053 280 CE 722.300722.309 123.133 300 D Turbo 617.952 722.315 1982–1985 USA only 123.153 300 CD Turbo 123.193 300 TD Turbo 722.303 1981–1982722.315 1982–1985 1985–1996 W 124 1995–1996 W 210 S-Class 1979–1991 W 126 1981–1991 W 126 Coupé 1991–1996 W 140 1992–1996 C 140 SL-Class 1981–1989 R 107 and C 107 1989–1996 R 129 Porsche 1984–1991 928 W4A 028 (Type 722.3) G-Class 1990–1996 463 W4A 020 (Type 722.4) C-Class 1982–1993 W 201 1993–1996 W 202 E-Class 123.220 200 102.920102.939 722.406 123.280 200 T 123.223 230 E 102.980 722.401 123.283 230 TE 123.243 230 CE 123.120 200 D 615.940 722.407 123.123 240 D 616.912 722.404 123.183 240 TD 123.125 240 D Lang 123.130 300 D 617.912 722.405 123.190 300 TD 123.132 300 D Lang 123.133 300 D Turbo 617.952 722.416 1985 California only 123.153 300 CD Turbo 123.193 300 TD Turbo 1985–1996 W 124 1995–1996 W 210 W5A 030 (Type 722.5) E-Class 1990–1996 W 124 1995–1996 W 210 S-Class 1991–1996 W 140 1992–1996 C 140 SL-Class 1990–1996 R 129

See also

List of Mercedes-Benz transmissions

Notes

References