With Assessment |
Planetary Gearset: Teeth[a][b] |
Count |
Total[c] Center[d] |
Avg.[e] |
|
Model Type |
Version First Delivery |
S1[f] R1[g] |
S2[h] R2[i] |
S3[j] R3[k] |
S4[l] R4[m] |
Brakes Clutches |
Ratio Span |
Gear Step[n] |
Gear Ratio |
R
 |
1
 |
2
 |
3
 |
4
 |
5
 |
6
 |
7
 |
8
 |
Step[n] |
[o] |
 |
[p] |
 |
 |
 |
 |
 |
 |
Δ Step[q][r] |
|
|
 |
 |
 |
 |
 |
 |
|
Shaft Speed |
 |
 |
 |
 |
 |
 |
 |
 |
 |
Δ Shaft Speed[s] |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|
8L90-M5U 8L80-MFC |
900 N⋅m (664 lb⋅ft)[11] 2014[t] |
41[12] 79 |
46 86 |
37 73 |
25 89 |
2 3 |
6.9991 1.7236 |
1.3204[n] |
Gear Ratio |
−3.8176[o]
 |
4.5600
 |
2.9709[r]
 |
2.0751
 |
1.6876[n][r][s]
 |
1.2700[r]
 |
1.0000
 |
0.8455[r][s]
 |
0.6515
 |
Step |
0.8372[o] |
1.0000 |
1.5349 |
1.4317 |
1.2297[n] |
1.3288 |
1.2700 |
1.1828 |
1.2977 |
Δ Step[q] |
|
|
1.0721[r] |
1.1643 |
0.9254[r] |
1.0463[r] |
1.0738 |
0.9114[r] |
|
Speed |
-1.1945 |
1.0000 |
1.5349 |
2.1975 |
2.7021 |
3.5905 |
4.56 |
5.3933 |
6.9991 |
Δ Speed |
1.1945 |
1.0000 |
0.5349 |
0.6626 |
0.5047[s] |
0.8884 |
0.9695 |
0.8333[s] |
1.6057 |
|
8L45 M5N |
550 N⋅m (406 lb⋅ft) 2015[u] |
41 79 |
41 79 |
41 79 |
26 94 |
2 3 |
7.0107 1.7431 |
1.3208[n] |
Gear Ratio |
−3.9278[o]
 |
4.6154
 |
3.0385[r]
 |
2.0648
 |
1.6583[n][r][s]
 |
1.2587[r]
 |
1.0000
 |
0.8494[r][s]
 |
0.6583
 |
Step |
0.8510[o] |
1.0000 |
1.5190 |
1.4715 |
1.2451[n] |
1.3175 |
1.2587 |
1.1773 |
1.2902 |
Δ Step[q] |
|
|
1.0322[r] |
1.1819 |
0.9450[r] |
1.0468[r] |
1.0691 |
0.9125[r] |
|
Speed |
-1.1751 |
1.0000 |
1.5190 |
2.2353 |
2.7831 |
3.6669 |
4.6154 |
5.4338 |
7.0107 |
Δ Speed |
1.1751 |
1.0000 |
0.5190 |
0.7163 |
0.5479[s] |
0.8837 |
0.9485 |
0.8184[s] |
1.5769 |
|
Ratio[v] R & even |
 |
 |
 |
 |
 |
Ratio[v] odd |
 |
 |
 |
 |
Algebra And Actuated Shift Elements[w] |
Brake A[x] |
❶ |
❶ |
❶ |
|
|
|
|
❶ |
❶ |
Brake B[y] |
❶ |
❶ |
❶ |
❶ |
❶ |
❶ |
|
|
|
Clutch C[z] |
|
❶ |
|
❶ |
|
❶ |
❶ |
❶ |
|
Clutch D[aa] |
❶ |
|
|
|
❶ |
❶ |
❶ |
❶ |
❶ |
Clutch E[ab] |
|
|
❶ |
❶ |
❶ |
|
❶ |
|
❶ |
|
8HP70 [ac][ad] |
700 N⋅m (516 lb⋅ft) 2008 |
48[13] 96 |
48[13] 96 |
69[2] 111 |
23[2] 85 |
2 3 |
7.0435 1.7693 |
1.3216[n] |
Gear Ratio |
−3.2968[o]
 |
4.6957
 |
3.1304[r]
 |
2.1039
 |
1.6667[n][r][s]
 |
1.2845[r]
 |
1.0000
 |
0.8392[r][s]
 |
0.6667
 |
Step |
0.7021[o] |
1.0000 |
1.5000 |
1.4879 |
1.2623[n] |
1.2975 |
1.2845 |
1.1917 |
1.2587 |
Δ Step[q] |
|
|
1.0081[r] |
1.1787 |
0.9729[r] |
1.0101[r] |
1.0779 |
0.9467[r] |
|
Speed |
-1.4243 |
1.0000 |
1.5000 |
2.2319 |
2.8174 |
3.6555 |
4.6957 |
5.5965 |
7.0435 |
Δ Speed |
1.4243 |
1.0000 |
0.5000 |
0.7319 |
0.5855[s] |
0.8382 |
1.0401 |
0.9000[s] |
1.4478 |
|
Ratio[ae]
R & Even |
 |
 |
 |
 |
 |
Ratio[ae] Odd |
 |
 |
 |
 |
|
All 8L-transmissions are based on a dedicated 8-speed layout, first realized in the ZF 8HP 70 gearbox
Layout
- Input and output are on opposite sides
- Planetary gearset 1 is on the input (turbine) side
- Input shafts are C2 and, if actuated, R1 and S4
- Output shaft is C4 (planetary gear carrier of gearset 4)
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
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
Average Gear Step

- With decreasing step width
- the gears connect better to each other
- shifting comfort increases
Sun 1: sun gear of gearset 1
Ring 1: ring gear of gearset 1
Sun 2: sun gear of gearset 2
Ring 2: ring gear of gearset 2
Sun 3: sun gear of gearset 3
Ring 3: ring gear of gearset 3
Sun 4: sun gear of gearset 4
Ring 4: ring gear of gearset 4
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 3) is always larger
- and the upper half of the gear steps (between the large gears; rounded up, here the last 4) 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)
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)
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)
From large to small gears (from right to left)
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)
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)
Adjusted formulas with gearset 1 and 3 swapped
Permanently coupled elements
- S1 and R2
- C1 (carrier 1) and C4 (carrier 4)
- S2 and S3
- C3 (carrier 3) and R4
Couples C2 and S4 with the turbine
Couples S1 and R2 with S4
without generation designation
First transmission on the market to use the dedicated 8-speed layout
- gearset 1 and 3 not swapped
- for comparison purposes only
Original formulas
- gearset 1 and 3 not swapped
- for comparison purposes only
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