Eisspeedway

Mercedes-Benz 4G-Tronic transmission

Mercedes-Benz W4A 040 · W4A 020
W4A 028 · W5A 030
Overview
ManufacturerDaimler AG
Production1979–1996
Body and chassis
Class4-speed longitudinal automatic transmission
Chronology
PredecessorMercedes-Benz first series automatic transmission
Successor5G-Tronic

Mercedes-Benz 4G-Tronic transmission is the unofficial name given to the transmission by car enthusiasts. It was produced from 1979 to 1996 in W4A 040, W4A 028 (both type 722.3), W4A 020 (type 722.4), and W5A 030 (type 722.5) variants.

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.

Gear Ratios[a]
Gear
Model
R 1 2 3 4 5 Total
Span
Span
Center
Avg.
Step
Compo-
nents
W4A 040 I · 1979 −5.139 3.676 2.412 1.436 1.000 3.676 1.917 1.543 3 Gearsets
3 Brakes
2 Clutches
W4A 020 · 1982 −5.669 4.249 2.408 1.487 1.000 4.249 2.061 1.620
W4A 040 II · 1985 −5.586 3.871 2.247 1.436 1.000 3.871 1.967 1.570
W4A 028 · 1990 −5.586 3.871 2.247 1.436 1.000 3.871 1.967 1.570
W5A 030 · 1990 −5.586 3.871 2.247 1.436 1.000 0.750 5.161 1.704 1.507 4 Gearsets
4 Brakes
3 Clutches
  1. ^ Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage

Specifications

Basic concept

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.

Layout

For this W4A-models 4 forward gears[a] using 8 main components[b][1][2] show economic equivalence with the direct predecessor.[c] 5 forward gears[d] out of 11 main components[e][1][2] and the need of 2 housings[f] and 2 different controls[g] 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,[h] 1 housing and 1 control.[i]

  1. ^ plus 1 reverse gear
  2. ^ 3 planetary gearsets (of which 2 gearsets are combined as a Ravigneaux compound gearset), 3 brakes, 2 clutches
  3. ^ 3 simple planetary gearsets, 3 brakes, 2 clutches
  4. ^ plus 1 reverse gear
  5. ^ 4 planetary gearsets (of which 2 gearsets are combined as a Ravigneaux compound gearset), 4 brakes, 3 clutches
  6. ^ regular bousing for gear 1 to 4 and reverse gear · supplemental housing for gear 5
  7. ^ hydraulic for gear 1 to 4 and reverse gear · electronic for gear 5
  8. ^ 3 simple planetary gearsets, 3 brakes, 3 clutches
  9. ^ electronic
Gear Ratios
With Assessment Planetary Gearset: Teeth[a] Count Total[b]
Center[c]
Avg.[d]
Ravigneaux Simple
Model
Type
Version
First Delivery
S1[e]
R1[f]
S2[g]
R2[h]
S3[i]
R3[j]
S4[k]
R4[l]
Brakes
Clutches
Ratio
Span
Gear
Step[m]
Gear
Ratio
R
1
2
3
4
5
Step[m] [n] [o]
Δ Step[p][q]
Shaft
Speed
Δ Shaft
Speed[r]
W4A 040 I
722.3
40 kp⋅m (289 lb⋅ft)
1979[1][2]
34
50
50
78
34
78
3
2
3.6759
1.9173
1.5433[m]
Gear
Ratio
−5.1388[n]
3.6759
2.4123[m][q]
1.4359[m]
1.0000
Step 1.3980[n] 1.0000 1.5238[m] 1.6800[m] 1.4359
Δ Step[p] 0.9070[q] 1.1700
Speed -0.7153 1.0000 1.5238 2.5600 3.6759
Δ Speed 0.7153 1.0000 0.5238 1.0362 1.1159
W4A 020
722.4
20 kp⋅m (145 lb⋅ft)
1982[1][2]
26
42
42
78
38
78
3
2
4.2491
2.0613
1.6197[m]
Gear
Ratio
−5.6692[n]
4.2491
2.4078[o]
1.4872
1.0000
Step 1.3342[n] 1.0000 1.7647[o] 1.6190 1.4872
Δ Step[p] 1.0900 1.0887
Speed -0.7153 1.0000 1.76478 2.8571 4.2491
Δ Speed 0.7153 1.0000 0.7647 1.0924 1.3919
W4A 040 II
722.3
40 kp⋅m (289 lb⋅ft)
1985[1]
26
46
46
78
34
78
3
2
3.8707
1.9674
1.5701[m]
Ratio −5.5857[n] 3.8707 2.2475[o] 1.4359 1.0000
W4A 028
722.3
28 kp⋅m (203 lb⋅ft)
1990[1]
26
46
46
78
34
78
3
2
3.8707
1.9674
1.5701[m]
Ratio −5.5857[n] 3.8707 2.2475[o] 1.4359 1.0000
W5A 030
722.5
30 kp⋅m (217 lb⋅ft)
1990[1]
26
46
46
78
34
78
26
78
4
3
5.1609
1.7038
1.5072[m]
Gear
Ratio
−5.5857[n]
3.8707
2.2475[o]
1.4359
1.0000
0.7500
Step 1.4431[n] 1.0000 1.7222[o] 1.5652 1.4359 1.3333
Δ Step[p] 1.1003 1.0901 1.0769
Speed -0.6930 1.0000 1.7222 2.6957 3.8707 5.1609
Δ Speed 0.6930 1.0000 0.7222 0.9734 1.1750 1.2902
Ratio
R & Even
Ratio
Odd
Algebra And Actuated Shift Elements
Brake A[s]
Brake B[t]
Brake R[u]
Brake S[v]
Clutch E[w]
Clutch F[x]
Clutch S[y]
  1. ^ Layout
    • Input and output are on opposite sides
    • Planetary gearset 1 (the inner Ravigneaux gearset) is on the input (turbine) side
    • Input shafts is S2
    • Output shaft is C3 (the carrier of gearset 3)
    • Output shaft W5A 030 is R4
  2. ^ Total Ratio Span (Total Ratio Spread · Total Gear Ratio)
    • A wider span enables the
      • downspeeding when driving outside the city limits
      • increase the climbing ability
        • when driving over mountain passes or off-road
        • or when towing a trailer
  3. ^ Ratio Span's Center
    • The center indicates the speed level of the transmission
    • Together with the final drive ratio
    • it gives the shaft speed level of the vehicle
  4. ^ Average Gear Step
    • With decreasing step width
      • the gears connect better to each other
      • shifting comfort increases
  5. ^ Sun 1: sun gear of gearset 1: inner Ravigneaux gearset
  6. ^ Ring 1: ring gear of gearset 1: inner Ravigneaux gearset
  7. ^ Sun 2: sun gear of gearset 2: outer Ravigneaux gearset
  8. ^ Ring 2: ring gear of gearset 2: outer Ravigneaux gearset
  9. ^ Sun 3: sun gear of gearset 3
  10. ^ Ring 3: ring gear of gearset 3
  11. ^ Sun 4: sun gear of gearset 4 · W5A 030 only
  12. ^ Ring 4: ring gear of gearset 4 · W5A 030 only
  13. ^ a b c d e f g h i j k Standard 50:50
    — 50 % Is Above And 50 % Is Below The Average Gear Step —
    • With steadily decreasing gear steps (yellow highlighted line Step)
    • and a particularly large step from 1st to 2nd gear
      • the lower half of the gear steps (between the small gears; rounded down, here the first 1 · W5A 030: the first 2) is always larger
      • and the upper half of the gear steps (between the large gears; rounded up, here the last 2) is always smaller
    • than the average gear step (cell highlighted yellow two rows above on the far right)
    • lower half: smaller gear steps are a waste of possible ratios (red bold)
    • upper half: larger gear steps are unsatisfactory (red bold)
  14. ^ a b c d e f g h i Standard R:1
    — Reverse And 1st Gear Have The Same Ratio —
    • The ideal reverse gear has the same transmission ratio as 1st gear
      • no impairment when maneuvering
      • especially when towing a trailer
      • a torque converter can only partially compensate for this deficiency
    • Plus 11.11 % minus 10 % compared to 1st gear is good
    • Plus 25 % minus 20 % is acceptable (red)
    • Above this is unsatisfactory (bold)
  15. ^ a b c d e f g Standard 1:2
    — Gear Step 1st To 2nd Gear As Small As Possible —
    • With continuously decreasing gear steps (yellow marked line Step)
    • the largest gear step is the one from 1st to 2nd gear, which
      • for a good speed connection and
      • a smooth gear shift
    • must be as small as possible
      • A gear ratio of up to 1.6667:1 (5:3) is good
      • Up to 1.7500:1 (7:4) is acceptable (red)
      • Above is unsatisfactory (bold)
  16. ^ a b c d From large to small gears (from right to left)
  17. ^ a b c Standard STEP
    — From Large To Small Gears: Steady And Progressive Increase In Gear Steps —
    • Gear steps should
      • increase: Δ Step (first green highlighted line Δ Step) is always greater than 1
      • As progressive as possible: Δ Step is always greater than the previous step
    • Not progressively increasing is acceptable (red)
    • Not increasing is unsatisfactory (bold)
  18. ^ Standard SPEED
    — From Small To Large Gears: Steady Increase In Shaft Speed Difference —
    • Shaft speed differences should
      • increase: Δ Shaft Speed (second line marked in green Δ (Shaft) Speed) is always greater than the previous one
    • 1 difference smaller than the previous one is acceptable (red)
    • 2 consecutive ones are a waste of possible ratios (bold)
  19. ^ Blocks S1 (sun gear of the inner Ravigneaux gearset)
  20. ^ Blocks S3
  21. ^ Blocks C1 and C2 (the common Ravigneaux carrier 1 + 2)
  22. ^ Blocks S4 (S: german "schnell" for fast) · W5A 030 only
  23. ^ Couples S1 (the sun gear of the inner Ravigneaux gearset) with C1 and C2 (the common Ravigneaux carrier 1 + 2)
  24. ^ Connects R2 and S3
  25. ^ Couples S4 with R4 (S: german "schnell" for fast) · W5A 030 only

Applications

The 4G-Tronic has been used in many Mercedes-Benz cars.

W4A 040 I+II (Type 722.3)

W4A 028 (Type 722.3)

W4A 020 (Type 722.4)

W5A 030 (Type 722.5)

See also

References

  1. ^ a b c d e f g Hans Joachim Foerster · Automatische Fahrzeuggetriebe · Page 171 and 192 · Berlin and Heidelberg 1991 · Print ISBN 978-3-642-84119-4 · Online ISBN 978-3-642-84118-7
  2. ^ a b c d Mercedes 722.3 & 722.4 Technical Overview