CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Caterpillar


Transmission Shifting Function

Usage:

CX28 TBB

Auto Neutral Function

The auto neutral function is used to neutralize the transmission when an external attachment is activated. This function can be programmed to shift back out of neutral if conditions warrant automatically. The function may also require the operator to reselect direction again. There are a set of programmable parameters to activate the auto neutral functionality and tailor the parameter to the application.

The auto neutral function parameter will essentially disable the whole feature if programmed to DISABLED. The auto neutral inputs will not affect the transmission if this feature is programmed to DISABLED. The second parameter, auto neutral switch type, defines the switch inputs used for the auto neutral function. The switch can be a single input SWC input, single input SWB, or a dual input SWC input.

The following is the input for the single switch to common:

Table 1
Auto Neutral Switch Programming     Connection or Data Link Source    
Switch To Sensor Common Ground     C16:34    
Dual Switch to Sensor Common Ground     C16: 34
C16: 15    
Switch To Battery 1     C16: 15    
Switch To Battery 2     Not Available    
Parking Brake     C16: 31,
J1939 Cab Controller
J1939 Instrument Cluster
J1939 Body Controller    

The following is the input for the switch to battery.

Table 2
Auto Neutral Input
SWB    
Auto Neutral State    
+BATT     Disabled    
Open     Enabled    

Direction Shift Inhibit Function

The Direction Shift Inhibit Function feature is used to prevent ALL shifts into Forward or Reverse unless a switch input is open. The Direction Shift Inhibit Function provides the ability for inhibiting ALL shifts into Forward or Reverse due to external equipment of the vehicle in operation. This function requires a switch input and programmable parameters through the service tool. If this function is enabled via the programmable parameter, then the function must be integrated in the vehicle wiring. This input can be used in order to prevent unwanted shifts out of neutral when external equipment is operating or other vehicle functions such as a seat switch.

When the Direction Inhibit Function Configuration parameter is programmed to "Enabled for Reverse," the transmission will not allow shifts into Reverse unless the switch input at C16: 32 is open. Attempts to shift into Reverse with the switch closed will result in the shift pad displaying a flashing "R" and an N indicating that the requested shift is not allowed.

When the Direction Inhibit Function Configuration parameter is programmed to "Enabled for Forward", the transmission will not allow shifts into Forward unless the switch input at C16: 32 is open. Attempts to shift into Forward with the switch closed will result in the shift pad displaying a flashing "6" and an N indicating that the requested shift is not allowed.

When the Direction Inhibit Function Configuration is programmed to "Enabled for Forward and Reverse" the transmission will not allow shifting into either Forward or Reverse unless the switch input at C16: 32 is open. Attempts to shift into Forward or Reverse with the switch closed will result in the shift pad displaying a flashing "R" or a flashing "6" and an N indicating that the requested shift is not allowed.

Note: If the switch is closed and the direction inhibit is enabled while the transmissin is in gear, the transmission will remain in the active gear. Once the transmission is shifted in to Neutral by selecting "N" on the shifter, any attempt to shift in to a gear that is selected for inhibit will be prohibited.

The function is configurable using the Cat ET service tool. The direction inhibit switch type parameter is used to specify whether a single switch SWC or SWB type inputs is used.

Table 3
Neutral To Gear Inhibit Switch Interaction @ C16: 32    
Switch State     Contact State     Allow Shift Into Selected    
OFF     Open     YES    
ON     Closed     NO    

Lockup Clutch Function

The lockup clutch controls the direct drive electrically. When the ECU activates the lockup solenoid, the lockup clutch in the torque converter mechanically connects the torque converter input shaft to the torque converter output shaft. This mechanically connects the transmission to the engine.

The ECU keeps the lockup clutch engaged as much as possible during normal operation. The vehicle is in torque converter drive when the lockup solenoid is deactivated.

The transmission reverse gear and the transmission neutral gear are torque converter drive. First gear is torque converter drive. The second gear is torque converter drive during slower vehicle speed and direct drive on the high end during higher vehicle speeds. The third gear and all other forward transmission gears are direct drive. Direct drive means that the transmission output shaft is mechanically connected to the input shaft.

Neutral To Gear Inhibit Function

The neutral to gear inhibit function provides the ability for inhibiting shifts out of NEUTRAL due to external equipment of the vehicle in operation. This function requires a switch input and programmable parameters through the service tool. If this function is enabled via the programmable parameter, then the function must be integrated in the vehicle wiring. This input can be used in order to prevent unwanted shifts out of neutral when external equipment is operating or other vehicle functions such as a seat switch. Cycle the keyswitch in order to activate the feature after any parameter has been changed.

When the Neutral to Gear Inhibit Function Configuration parameter is programmed to "Enabled for Reverse" the transmission will not allow shifts from Neutral into Reverse unless the switch input at C16: 8 is open. Attempts to shift into Reverse with the switch closed will result in the shift pad displaying a flashing "R" and an N indicating that the requested shift is not allowed.

When the Neutral to Gear Inhibit Function Configuration parameter is programmed to "Enabled for Forward" the transmission will not allow shifts from Neutral into Forward unless the switch input at C16: 8 is open. Attempts to shift into Forward with the switch closed will result in the shift pad displaying a flashing "6" and an N indicating that the requested shift is not allowed.

When the Neutral to Gear Inhibit Function Configuration is programmed to "Enabled for Forward and Reverse" the transmission will not allow shifting from Neutral into either Forward or Reverse unless the switch input at C16: 8 is open. Attempts to shift into Forward or Reverse with the switch closed will result in the shift pad displaying a flashing "R","6" and an N indicating that the requested shift is not allowed.

Table 4
Neutral To Gear Inhibit Switch Interaction @ C16: 8    
Switch State     Contact State     Allow Shift IntoSelected Range from Neutral    
OFF     Open     YES    
ON     Closed     NO    

Rapid Downshift Function

The ECU does not allow a turn around shift until a short time after a shift occurs. A turnaround shift is an opposite shift from the previous shift. For example, a downshift is prevented for a short time after an upshift and an upshift is prevented for a short time after a downshift. The turnaround feature allows the conditions to stabilize before an opposite shift. The delay prevents hunting between gears.

Elevated Downshift Function

This function improves retarding performance by elevating the upshift and the downshift points.

When the engine retarder is on, the upshift and downshift points are raised because the retarder systems are more effective at higher engine speeds.

Transmission PTO Control Selection

The transmission PTO feature controls the PTO enable output driver at C18:6. The PTO enable driver is used to control an OEM supplied control system. The system is connected to the transmission's auxiliary output shaft. This output is capable of driving 2 Amps and will be turned ON when all of the programmed conditions have been met.

This function requires an SWC input, an Output Driver, and a set of programmable parameters that are controlled by the service tool. The PTO Control function reads a PTO switch input in order to direct it to turn on the PTO driver.

Table 5
PTO Switch Input Configuration     Connection or Data link Source    
Switch To Common Ground     C16: 38    
Dual Switch to Common Ground     Not Available    
Switch To Battery 1     Not Available    
Switch To Battery 2     Not Available    
Switch To Battery 3     Not Available    

Each system has specific operational conditions that must be met. The operational conditions are set by accessing the programmable parameters with the service tool.

The following items are available for tailoring the PTO operation for a specific vehicle:

PTO Mode Enable - The PTO mode enable parameter must be programmed to enabled before any of the other parameters will be in effect.

PTO Mode Neutral Restriction - The PTO neutral restriction parameter is used to restrict the PTO operation to NEUTRAL. The PTO "ON/OFF" switch status will be ignored when the transmission is not in NEUTRAL.

PTO Mode Gear Limit - The PTO mode gear limit parameter is used to limit the maximum gear that the PTO enable output may be energized. When programmed to FIRST gear, then the PTO enable output may be energized when in NEUTRAL, REVERSE, or FIRST gear. The PTO operation will be blocked the transmission is in SECOND gear or a higher gear.

PTO Mode Maximum Engine Speed for Engagement - The PTO enable output can be restricted from energizing at too high of an engine RPM.

PTO Mode Maximum Engine Speed for Operation - This feature limits the PTO operation to below the programmed engine RPM. When the engine rises above the programmed limit, the PTO enable output will de-energize.

PTO Mode Maximum Engine Speed for Engagement - This feature is used in order to prevent the PTO enable output from energizing above the programmed RPM.

PTO Maximum Engine Speed for Operation - This feature is used to limit the PTO operation to below the programmed transmission output shaft speed. When the output shaft speed rises above the programmed limit, the PTO enable output will be de-energized.

Transmission Default and Alternate Shift

Schedule Configurations

The transmission software allows for two shift schedules to be present in memory. A switch input at C16:14 allows for switching between these two shift schedules. When the switch is Open, the shift schedule programmed into the Transmission Default Shift Schedule will control the transmission's shifting.

When the switch is closed, the shift schedule programmed into the Transmission Alternate Shift Schedule will control the transmission's shifting.

Transmission Default and Alternate Maximum Gear

Two parameters allow for programming the Default and Alternate shift schedules maximum gear of operation. The default setting for both shift schedules is disabled. any available gear may be selected. The shift selector will reflect the programmed value on the left digit of the gear display. The transmission will limit operation to this programmed gear. This function occurs unless an upshift is required to prevent an engine over speed event.

Hold GearFunction

This function requires a momentary switch input to allow for holding the current gear as the maximum gear for operation. When the switch input at C16: 40 is closed, the transmission will attempt to hold the current gear. The transmission will only upshift at the engine over speed point. Normal downshifting is allowed as the vehicle slows down. As the transmission downshifts, the hold continues. In other words this means that the transmission will stay in the downshifted gear unless the engine over speed point forces it to upshift again.

Table 6
Hold Function Input Configuration     Function Input    
Disabled     N/A    
SWC     C 16: 40    

Options are Disabled feature will function

J1939 - ( Input Switch is the MODE button), or switch to ground.

Quick Gear Limit

The Quick Gear Limit feature is used to limit the transmission gear selection to First Gear Forward and Reverse Gear. Two parameters must be programmed to enable this feature. The Quick First Gear Limit Configuration parameter must be programmed to either Enabled to First Gear and Do Not Lock Out Reverse or Enabled to First gear and Inhibit Shifts to Reverse to affect transmission operation. Programming to Disabled will cause the feature not to function.

The Quick Gear Limit Switch Configuration parameter must be programmed to either Switch to common ground or Switch to battery 1 to enable the Quick Gear limit feature.

The Quick Gear Limit Feature utilizes an OEM installed switch circuit. This feature can be used to effectively limit vehicle speed during vehicle maneuvering or stop-and-go driving during refuse applications. Further, the reverse range may be inhibited during Quick Gear Limiting if desired. The Quick Gear Limit feature only inhibits upshifts past onest gear. If the transmission is above 2nd gear, the transmission will continue to operate normally until 2nd gear is attained, at which time upshift will normally be inhibited. Vehicle operation conditions sufficient to over speed the engine in 1st gear will result in an engine-protection upshift to higher gears.

Quick Gear Limit Function Customer Parameter Programming -

Programming as shown enables the Quick Gear Limit function:

Quick Gear Limit Switch Customer Parameter Programming - The quick Gear Limit switch may be programmed to any one of two inputs. One switch to battery positive, and one switch to sensor common input.

Table 7
Input Contact     Description    
C16: 6     Switch to sensor common input for the Quick Gear Limit function.    
C16:26     Switch to battery input for the Quick Gear Limit function.    

Quick Gear Limit Input-Switch to Battery - The Quick Gear Limit Input may be configured as a switch-to-battery input, using switch-to-battery inputs available on the transmission control at C16: 26.

Quick Gear Limit Input-Switch to Common - The Quick Gear Limit Input is configured as a switch to common.

Quick Gear Limit Logic - The Quick Gear Limit feature only limits the transmission-selected gear to onest forward, or 1st forward and onest reverse. If the transmission is in 3rd or higher gear when the Quick Gear Limit Switch is ON, the transmission will not effect the transmissions shift points. IF the transmission is in 2nd gear or lower, the transmission will inhibit upshifts until the Quick Gear Limit switch is OFF.

Caterpillar Information System:

CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3823 - FMI 4
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3823 - FMI 3
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3823 - FMI 16
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3509 - FMI 4
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3509 - FMI 3
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3463 - FMI 2
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3027 - FMI 4
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3027 - FMI 3
Reuse and Salvage of Transmission Components {3030} Reuse and Salvage of Transmission Components {3030}
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 191 - FMI 8
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 191 - FMI 14
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 190 - FMI 8
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System System Protection Functions
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Additional Functions
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 3825 - FMI 8
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 513 - FMI 19
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Programmable Parameters
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 513 - FMI 9
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 525 - FMI 9
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission Control
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 639 - FMI 14
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 639 - FMI 9
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 734 - FMI 3
CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Transmission, SPN 734 - FMI 5
Back to top
The names Caterpillar, John Deere, JD, JCB, Hyundai or any other original equipment manufacturers are registered trademarks of the respective original equipment manufacturers. All names, descriptions, numbers and symbols are used for reference purposes only.
CH-Part.com is in no way associated with any of the manufacturers we have listed. All manufacturer's names and descriptions are for reference only.