Need to find out how to diagnose & repair an electronic split shift for case IH CX80 tractor. At present in low range and not shifting with button electric control. No noise of solenoid can be heard on shifting button so assume a problem in electrics. Been trying to find wiring diagrams with no luck, cheers, Peter

Have it check for DTC'S - diagnostic trouble codes ?
GEM Diagnostic Trouble Code (DTC) Index
GEM Diagnostic Trouble Code (DTC) Index DTC Description Source Action C1728 Transfer Case Unable to Transition Between 2H and 4H GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. C1729 Transfer Case Unable to Transition Between 4H and 4L GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P0500 Vehicle Speed Sensor (VSS) Malfunction GEM GO to Pinpoint Test F . P1804 Transmission 4-Wheel Drive High Indicator Circuit Failure GEM GO to Pinpoint Test H . P1808 Transmission 4-Wheel Drive Low Indicator Circuit Failure GEM GO to Pinpoint Test I . P1812 Transmission 4-Wheel Drive Mode Select Circuit Failure GEM GO to Pinpoint Test E . P1815 Transmission 4-Wheel Drive Mode Select Short Circuit to Ground GEM GO to Pinpoint Test E . P1819 Transmission Park/Neutral Position Switch Short Circuit to Ground GEM GO to Pinpoint Test F . P1820 Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1822 Transmission Transfer Case Clockwise Shift Relay Coil Short to Battery GEM GO to Pinpoint Test E . P1828 Transfer Case Counterclockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1830 Transmission Transfer Case Counterclockwise Shift Relay Coil Short Circuit to Battery GEM GO to Pinpoint Test E . P1832 Transmission Transfer Case Differential Lockup Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1834 Transmission Transfer Case Differential Lockup Solenoid Short Circuit to Battery GEM GO to Pinpoint Test G . P1865 Transmission Transfer Case Contact Plate Power Short to Ground GEM GO to Pinpoint Test E . P1866 Transmission Transfer Case System Concern - Servicing Required GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P1867 Transmission Transfer Case Contact Plate General Circuit Failure GEM GO to Pinpoint Test E . P1876 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1877 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Short to Battery GEM GO to Pinpoint Test G . - For All Other DTCs GEM GO to Section 419-10 .
Your best bet , take it to a qualified repair shop that has the diagnostic tool to trouble shoot .
Principles of Operation
Transfer Case - Electronic Shift
The four-wheel drive, electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4X4 HIGH, and 4X4 LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators, one for 4X4 HIGH which is 4X4, and one for 4X4 LOW which is LOW RANGE (in 4X4 LOW both the lamps are on). Shifts into 4X4 HIGH can be made at any speed. When shifting into 4X4 HIGH with the vehicle stationary, tooth blockage may occur, preventing shift completion. When the vehicle is driven above 8 km/h (5mph) the shift will complete. When shifting in or out of 4X4 LOW, the generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission). (The digital transmission range [TR] sensor informs the GEM when the automatic transmission is in the NEUTRAL range position.)
The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and the range fork within the transfer case between the 4X4 HIGH, 4X4 LOW, and 2WD range positions.
The GEM uses two relays to control the gearmotor encoder assembly shift between 4X4 HIGH, 4X4 LOW, and 2WD modes. The GEM controls the pulse vacuum hublock (PVH) solenoid which supplies engagement and disengagement vacuum to control the hublocks.
The GEM accomplishes shifts by interpreting inputs from:

• mode select switch (MSS)
• vehicle speed signal (transmitted from the ABS system)
• gearmotor encoder plate position
• brake pedal switch
• digital transmission range (TR) sensor (automatic transmission)
• clutch pedal position (CPP) switch (manual transmission)
• ignition switch

Based on these inputs, the GEM controls the shifts into 2WD, 4X4 HIGH, or 4X4 LOW with the following outputs:

• low to high relay (clockwise)
• high to low relay (counterclockwise)
• pulse vacuum hublock (PVH) solenoid
• gearmotor encoder assembly

The electronic shift-on-the-fly (ESOF) system has a feature which allows the driver to override the vacuum operated hublocks. When the front hublocks are manually turned to the LOCK position, the hublocks are locked at all times, overriding the vacuum operated system. If the front hublocks are manually turned to the AUTO position, the hublocks can only be locked by turning the MSS to 4X4 HIGH or 4X4 LOW position.

On the transfer case
Transfer Case - Electronic Shift
The four-wheel drive electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4WD HIGH, and 4WD LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators: one for 4WD HIGH which appears as 4WD, and one for 4WD LOW, which appears as 4WD LOW. Shifts into 4WD HIGH can be made at any speed. When shifting into 4WD HIGH with the vehicle stationary, tooth blockage may occur preventing shift completion. When the vehicle is driven above 8 km/h (5 mph) the shift will complete. When shifting in or out of 4WD LOW, the four-wheel drive (4WD) control module requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission be in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission).
The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4WD HIGH, 4WD LOW, and 2WD range positions.
The four-wheel drive (4WD) control module controls the gearmotor encoder assembly that shifts between 4WD HIGH, 4WD LOW, and 2WD modes.

talk with a case service center
normally the engine has to be split from the gear box case
specialist job requiring specialist equipment

It depends on what is wrong , is the 4x4 light flashing ? Are you aware of the complexity of the 4x4 system ? Has a electronic control module , has the ability to set an store DTC'S - diagnostic trouble codes !
Transfer Case The four wheel drive system is an electronic shift 4X4 system that allows the operator to choose between three different modes. The operator can switch 4X4 HIGH modes at any speed. To engage or disengage 4X4 LOW the vehicle speed must be less than 5 kph (3 mph), the brake depressed, and the transmission must be in NEUTRAL.
The shift motor sense plate, an integral part of the electronic shift motor, informs the generic electronic module (GEM) of the transfer case shift motor and contact plates A, B, C and D position.
The digital transmission range (TR) sensor is located on the LH side of the transmission, and informs the GEM when the transmission is in the NEUTRAL position.
The electronic shift motor is mounted externally at the rear of the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4X4 HIGH, 4X4 LOW and 2WD range positions.
When the GEM verifies the completion of the transfer case shift from 2WD to 4X4 HIGH (reading the contact plate positions), the GEM will then energize both pulse vacuum hublock (PVH) solenoids (supplying ground for 45 seconds). The PVH solenoid will allow a HIGH flow of intake manifold vacuum to the "wheel end hublocks", engaging the wheel end hubs to the front differential and transfer case to achieve four wheel drive.
Here are just a few DTC'S the system can set an store in the module !
P1804 4WD High Indicator Circuit Failure GEM GO to Pinpoint Test C . P1806 4WD High Indicator Short to Battery GEM GO to Pinpoint Test C . P1808 4WD Low Indicator Circuit Failure GEM GO to Pinpoint Test C . P1810 4WD Low Indicator Short to Power GEM GO to Pinpoint Test C . P1812 4WD Mode Select Switch Circuit Failure GEM GO to Pinpoint Test A . P1815 4WD Mode Select Switch Circuit Short to Ground GEM GO to Pinpoint Test A . P1820 Transfer Case CW Shift Relay Circuit - Failure GEM GO to Pinpoint Test A . P1822 Transfer Case CW Shift Relay Coil Short to Power GEM GO to Pinpoint Test A . P1824 4WD Electric Clutch Relay Circuit Failure GEM GO to Pinpoint Test A . P1826 4WD Low Clutch Relay Short to Power GEM GO to Pinpoint Test A . P1828 Transfer Case CCW Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test A . P1830 Transfer Case CCW Shift Relay Coil Short to Battery GEM GO to Pinpoint Test A . P1838 Transfer Case Shift Motor Circuit Failure GEM GO to Pinpoint Test A . P1846 Transfer Case CONTACT PLATE "A" Circuit Failure GEM GO to Pinpoint Test A . Now are you sure you really want to mess with this ? You would need a factory diagnostic scan tool to check this out before you start replacing parts !
Here

remove floor deck plate. follow linkage down to see if it is movimi into high or low range. if it is remove cover on side of rear end housing .(5sided cover, you should lose maybe 1-2 gallons of oil} look inside trans and move shift lever you should be able to see fork move if not remove shift cover to find broken or worn parts make sure no slop exists in linkage or under range cover

Manual shift or Four-Wheel Drive Systems - Electronic Shift I'm assuming you have electronic shift because you refer to relay clicking behind the instrument panel . Principles of Operation Transfer Case - Electronic Shift
The four-wheel drive, electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4X4 HIGH, and 4X4 LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators, one for 4X4 HIGH which is 4X4, and one for 4X4 LOW which is LOW RANGE (in 4X4 LOW both the lamps are on). Shifts into 4X4 HIGH can be made at any speed. When shifting into 4X4 HIGH with the vehicle stationary, tooth blockage may occur, preventing shift completion. When the vehicle is driven above 8 km/h (5mph) the shift will complete. When shifting in or out of 4X4 LOW, the generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission). (The digital transmission range [TR] sensor informs the GEM when the automatic transmission is in the NEUTRAL range position.)
The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and the range fork within the transfer case between the 4X4 HIGH, 4X4 LOW, and 2WD range positions.
The GEM uses two relays to control the gearmotor encoder assembly shift between 4X4 HIGH, 4X4 LOW, and 2WD modes. The GEM controls the pulse vacuum hublock (PVH) solenoid which supplies engagement and disengagement vacuum to control the hublocks.
The GEM accomplishes shifts by interpreting inputs from:

• mode select switch (MSS)
• vehicle speed signal (transmitted from the ABS system)
• gearmotor encoder plate position
• brake pedal switch
• digital transmission range (TR) sensor (automatic transmission)
• clutch pedal position (CPP) switch (manual transmission)
• ignition switch

Based on these inputs, the GEM controls the shifts into 2WD, 4X4 HIGH, or 4X4 LOW with the following outputs:

• low to high relay (clockwise)
• high to low relay (counterclockwise)
• pulse vacuum hublock (PVH) solenoid
• gearmotor encoder assembly

The electronic shift-on-the-fly (ESOF) system has a feature which allows the driver to override the vacuum operated hublocks. When the front hublocks are manually turned to the LOCK position, the hublocks are locked at all times, overriding the vacuum operated system. If the front hublocks are manually turned to the AUTO position, the hublocks can only be locked by turning the MSS to 4X4 HIGH or 4X4 LOW position.
Do you know what DTC'S - diagnostic trouble code's are ?
GEM Diagnostic Trouble Code (DTC) Index
GEM Diagnostic Trouble Code (DTC) Index DTC Description Source Action C1728 Transfer Case Unable to Transition Between 2H and 4H GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. C1729 Transfer Case Unable to Transition Between 4H and 4L GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P0500 Vehicle Speed Sensor (VSS) Malfunction GEM GO to Pinpoint Test F . P1804 Transmission 4-Wheel Drive High Indicator Circuit Failure GEM GO to Pinpoint Test H . P1808 Transmission 4-Wheel Drive Low Indicator Circuit Failure GEM GO to Pinpoint Test I . P1812 Transmission 4-Wheel Drive Mode Select Circuit Failure GEM GO to Pinpoint Test E . P1815 Transmission 4-Wheel Drive Mode Select Short Circuit to Ground GEM GO to Pinpoint Test E . P1819 Transmission Park/Neutral Position Switch Short Circuit to Ground GEM GO to Pinpoint Test F . P1820 Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1822 Transmission Transfer Case Clockwise Shift Relay Coil Short to Battery GEM GO to Pinpoint Test E . P1828 Transfer Case Counterclockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1830 Transmission Transfer Case Counterclockwise Shift Relay Coil Short Circuit to Battery GEM GO to Pinpoint Test E . P1832 Transmission Transfer Case Differential Lockup Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1834 Transmission Transfer Case Differential Lockup Solenoid Short Circuit to Battery GEM GO to Pinpoint Test G . P1865 Transmission Transfer Case Contact Plate Power Short to Ground GEM GO to Pinpoint Test E . P1866 Transmission Transfer Case System Concern - Servicing Required GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P1867 Transmission Transfer Case Contact Plate General Circuit Failure GEM GO to Pinpoint Test E . P1876 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1877 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Short to Battery GEM GO to Pinpoint Test G .
Your best bet , take it to a qualified repair shop .

Is the transfer case in High or Low range? If there are no codes present I would almost suspect that the transfer case is in Low range, because of those shift speeds.

1. • 1 Start your Dodge truck's engine.
     
   • 2 Turn the electronic transfer case from "2WD" to "4WD Lock" to engage the high range 4WD, if the dodge truck is equipped with an electronic transfer case; otherwise, shift the transfer case lever from "2H" to "4H." The electronic transfer case is located on the instrument panel and is marked with "2WD," "4WD Lock" and 4WD Low." The lever-equipped transfer case is located to the right of your leg and is marked with "2H," "4H" and "4L."
     
   • 3 Shift the transmission into "Neutral" while the vehicle is either stopped or rolling at 2 to 3 mph to begin engaging in the low range 4WD. Turn the electronic transfer case to "4WD Low," if the Dodge truck is equipped with an electronic transfer case; otherwise, shift the transfer case lever from "2H" or "4H" to "4L."
     
   Tips & Warnings
   • Indicator lights will come on and alert you that your vehicle is in either the high or low range of 4WD.
     
   • Do not engage in the low range of 4WD drive if the transmission is in gear; you must shift to "Neutral" first.
     
   • Many Dodge trucks allow you to shift from 2-wheel drive to the high range of 4WD at up to 55 mph--consult your truck's manual to ensure that this is possible. Do not exceed 55 mph while engaged in the high range of 4WD. Do not exceed 25 mph while engaged in the low range of 4WD.
     
   • Do not engage in 4WD unless you are on slipper or rocky roads.
     

the first thing to remember is that this transmission has straight cut gears that shift with a slide collar the tractor probabably will need to be brought almost to a complete stop to shift. if it continues to grind check clutch pedal adjustment and ta dump spool adjustment . then adjust trans brake . at1000-1200 rpm it should drop into gear with very little or no grinding

The transfer case is stuck in the low range. If manual shift try shifting from low to high several times to see if free up. If electronic, check all fuses and make sure you hear transfer case change range. Do this by shifting with key on engine off. If no change refer to qualified transmission mechanic.