Incorrect gear ratio on 6th gear
Contact an Allison dealer.
What you'll see
No driver-visible symptom recorded.
System reaction
The Allison fault code number is: P0729.The fault code is set under stationary conditions when the calculated gear ratio differs from the actual gear ratio for longer than 2 seconds.For the fault code to be set, the following conditions must be met: The hydraulic system is pressurised. No gear changing in progress.No continuous default hydraulic conditions.Output shaft speed higher than 200 rpm.No start up or shut down process of the engine in progress.The lock-up cannot be locked.The control unit shuts off gear changing adaptation.The control unit attempts to engage 5th gear. If this is not successful, the control unit specifies 3rd gear.While the fault code is active, the control unit ignores all information from the drive mode selector. The fault code is cleared automatically, when the vehicle has completed 40 start-up cycles without the fault being detected again.
Diagnostic depth
Actual 6th gear ratio does not agree with the calculated 6th gear ratio. Gear ratio is determined on the basis of turbine speed and output shaft speed. This measured gear ratio is compared with what the gear ratio should be for 6th gear.
This is probably caused by a mechanical problem, for example a problem with the C2 and C4 connectors for 6th gear.