Incorrect gear ratio on 4th gear
â–¶ How to fix
Contact an Allison dealer.
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
Detection
Actual 4th gear ratio does not agree with the calculated 4th 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 4th gear.
Possible cause
This is probably caused by a mechanical problem, for example a problem with clutches C1 and C2 for 4th gear.