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Low Speed Range Axle Ratio
OEM
High Speed Range Axle Ratio
OEM
FORMERLY: NOMINAL AXLE RATIO - HIGH SPEED RANGE AXLE RATIO
TWO-SPEED AXLE - LOW SPEED RANGE AXLE RATIO
Description:
These two parameters must be programmed when a
Two-Speed Axle On/Off Switch is used by the ECM in
order to adjust the vehicle speed calibration. When a
two-speed axle is used, the change in gear ratios from
the high speed range to the low speed range alters the
calibration of the Vehicle Speed Limit and Vehicle Speed
Calibration, which require a calibration adjustment to
ensure the ECM-driven speedometer and ECM-stored
information correctly refl ect the actual vehicle speed.
Available:
All electronically controlled on-highway engines
covered in this handbook
Range:
Engine
Range
Cat
Default
Minimum Maximum
Low
Speed
Range
High
Speed
Range
Low
Speed
Range
High
Speed
Range
3126E, C7, C9 0.00 0.00 19.99 9.99 0.00
C-10, C-12,
C-15, C-16,
C11, C13, C15
1.00 1.00 19.99 9.99 1.00
EPA’07 and
newer C7, C9,
C13, C15
1.00 1.00 19.99 19.99 1.00
Advantages:
Proper calculation of the Low Speed Range Axle
Ratio and High Speed Range Axle Ratio parameters is
essential for proper cruise control and speedometer (if
controlled by the ECM) operation, and accurate fl eet and
driver trip data.
Disadvantages:
None
Recommendations:
✔ Let the OEM calculate the Low Speed Range Axle
Ratio and High Speed Range Axle Ratio parameters
based on the truck specifi cations.
✔ Recalculate and program the Low Speed Range
Axle Ratio and High Speed Range Axle Ratio
parameters if any changes are made to the rear
axle ratios. Note that repairing or replacing the
rear end with the same axle ratio will not cause
a problem or require any recalculation for this
parameter.
Vehicle Speed Parameters