1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192 
Meres box with brains
Page 30
If you've noticed an error in this article please click here to report it so we can fix it.
Mercedes-Benz hasn't been a front runner in the race to develop full auto boxes for LGVs, but ifs finally caught up with the leaders. We've been getting to grips with Power-Shift 12. Colin Barnett reports.
The G211-12 Power-Shift is clearly designed to help Mercedes-Benz to catch up with the opposition's heavy truck automatic transmissions.
The G211-12 spearheads a family of 12-speed, non-synchromesh auto boxes, designed for engines developing between 320 and 440hp,with a maximum torque capacity of 2,100Nm.
The direct-drive G211 has a 142mm shaft spacing; the higher capacity G281 and overdrive G330 units will have 152mm spacings with torque limits of 2,800 and 3,300Nm respectively.
Actros operators will be able to opt for a G211 from September: it will cost some £1,700 more than the standardTelligent.The G281 and G330 will follow at the end of the year, with Axor versions arriving in the second half of 2007.
The Power-Shift 12 transmissions will supplement the synchromesh Power-Shift 16s. which cater for heavier duty applications.
On the three main ratios of the constant-mesh box,dog clutches are synchronised electronically with the aid of a layshaft brake. The rearmounted planetary range-change and frontmounted splitter unit provide the dozen ratios.
The controls could hardly be simpler. A familiar looking lever on the armrest provides the main control with a safety interlock button on the left and a neutral button on the right. In normal driving it's simply a matter of nudging the lever forward and pressing the throttle.
A button marked A/M toggles between auto and manual; a small paddle in front is used for split shifts in manual. Moving the main lever gives temporary manual control in auto mode.
Access to the more sophisticated functions is via a small bank of rocker switches on the dash. Press the top of the first one and you enter power mode,extending the rev range for better performance. before automatically reverting to economy after 10 minutes. The bottom of the switch turns off the 'ecoroll' coasting function.
The top of the second switch is for manoeuvring, which spreads the engine revs up to 1,00Orpm across the whole throttle pedal travel. The bottom is for vehicle rocking, giving fast switches between first and reverse to rock the truck out of snow or mud. Four reverse ratios are available for the brave. The final switch adjusts the cruise control over-run speed by 415km/h. Cruise control includes two memory settings and a speed limiter function.
On the road,changes are well timed,quick and smooth. The only disconcerting feature is that when moving away a torque control cushions the drive take-up, but feels like a lack of response.
We haven't quantified M-B's claim that shifts are 15% quicker than the old AutoTrans, but they certainly feel as fast as any competitor. •