S0607080K
Page 22
Transmission and Torque Converter
(ZF 4WG-310)
ABBREVIATIONS
Throughout this section the following abbreviations are used to indicate various conditions.
DEFINITION OF OPERATION MODES
Normal
There is no failure detected in transmission system or failure has no or slight effects on transmission
control. TCU will work without or in special cases with little limitations. (see following table)
Substitute Clutch Control
TCU cannot change gears or direction under control of normal clutch modulation. TCU uses substitute
strategy for clutch control. All modulations are only time controlled. (Comparable with EST 25)
Limp-home
The detected failure in the system has strong limitations to transmission control. TCU can engage only one
gear in each direction. In some cases only one direction will be possible. TCU will shift the transmission
into neutral at the first occurrence of the failure. First, the operator must shift the gear selector into neutral
position. If output speed is less than a threshold for neutral to gear and the operator shifts the gear selector
into forward or reverse, the TCU will select the limp-home gear. If output speed is less than a threshold for
reversal speed and TCU has changed into the limp-home gear and the operator selects a shuttle shift,
TCU will shift immediately into the limp-home gear of the selected direction. If output speed is greater than
the threshold, TCU will shift the transmission into neutral. The operator has to slow down the vehicle and
must shift the gear selector into neutral position.
Transmission Shut Down
TCU has detected a severe failure that disables control of the transmission. TCU will shut off the solenoid
valves for the clutches and also the common power supply (VPS1). Transmission shifts to Neutral. The
park brake will operate normally, also the other functions which use ADM 1 to ADM 8. The operator has to
slow down the vehicle. The transmission will stay in neutral.
TCU Shut Down
TCU has detected a severe failure that disables control of system. TCU will shut off all solenoid valves and
also both common power supplies (VPS1, VPS2). The park brake will engage, also all functions are
disabled which use ADM 1 to ADM 8. The transmission will stay in neutral.
Abbreviations
O.C. Open Circuit
S.C. Short Circuit
OP-Mode OPeration Mode
TCU Transmission Control Unit
ABS Anti Blocking System
ASR Anti Slipping Regulation
EEC Electronic Engine Controller
PTO Power Take Off
CCO Clutch Cut Off
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