RANGE SHIFT AIR SYSTEM—ALL MODELS
The Range Shift Air System consists of the air filter/ regulator, slave valve, a Range Control Valve or Mas- ter Control Valve, range cylinder, fittings and connecting air lines. See Air System Schematics.
CONSTANT AIR from the air filter/regulator is sup- plied to the “S” or Supply Port of slave valve and passed through to the INLET or “S” Port of control valve.
WHILE IN LOW RANGE, the control valve is OPEN and AIR is returned to slave valve at the “P” or End Port. This signals the valve to supply AIR in line be- tween the Low Range or “L” Port of slave valve and the Low Range Port of range cylinder housing. AIR received at this port moves the range piston to the rear and causes the auxiliary low range gear to be- come engaged.
WHILE IN HIGH RANGE, the control valve is CLOSED and NO AIR is returned to the slave valve. This signals the slave valve to supply AIR in line be- tween the High Range or “H” Port of valve and the High Range Port of range cylinder cover. AIR re- ceived at this port moves the range piston forward to engage the auxiliary drive gear with sliding clutch and bypass the low range gear set.
Range shifts can be made ONLY when the gear shift lever is in, or passing through, neutral. Thus, the range desired can be PRESELECTED while the shift lever is in -a gear position. As the lever is moved through neutral, the actuating plunger in the shift bar housing releases the slave valve, allowing it to move to the selected range position.
If the transmission fails to make a range shift or shifts too slowly, the fault may be in the Range Shift Air System or actuating components of the shift bar housing assembly.
To locate the trouble, the following checks should be made with normal vehicle air pressure applied to the system, but with the engine off.
CAUTION: NEVER WORK UNDER A VEHICLE WHILE ENGINE IS RUNNING as personal injury may result from the sudden and unintended movement of vehicle under power.
INCORRECT AIR LINE HOOK-UPS (See Air System Schematics) With the gear shift lever in neutral, move the con- trol that provides range selection UP and DOWN.
If the air lines are crossed between control valve and slave valve, there will be CON- STANT AIR flowing from the exhaust port of control valve WHILE IN HIGH RANGE.
If the air lines are crossed between the slave valve and range cylinder, the transmission gearing will not correspond with the range se- lection. A LOW RANGE selection will result in a HIGH RANGE engagement and vice versa.
With the gear shift lever in neutral, coat all air lines and fittings with soapy water and check for leaks, moving the control that provides range se- lection UP and DOWN.
If there is a steady leak from the exhaust port of control valve, O-rings and/or related parts of the control valve are defective.
If there is a steady leak from breather of slave valve: an O-ring in valve is defective, or there is a leak past O-rings of range cylinder piston.
If transmission fails to shift into LOW RANGE or is slow to make the range shift and the case is pressurized, see Check No. 7 of this section.
Tighten all loose connections and replace de- fective O-rings and parts.
3. AIR FILTER/REGULATOR (See illustration, Page 27.) With the gear shift lever in neutral, check the breather of air filter/regulator assembly. There should be NO AIR leaking from this port. The complete assembly should be replaced if a steady leak is found. Cut off the vehicle air supply to the air filter/ regulator assembly, disconnect the air line at fit- ting in Supply OUTLET and install an air gage in opened port. Bring the vehicle air pressure to nor- mal. Regulated air pressure should be 57.5 to 62.5 PSI.
DO NOT ADJUST SCREW AT BOTTOM OF REGU- LATOR TO OBTAIN CORRECT READINGS. The air regulator has been PREADJUSTED within the correct operating limits. Any deviation from these limits, especially with regulators that have been in operation for some time, is likely to be caused by dirt or worn parts. If replacement or cleaning of the filter element does nothing to correct the air pressure readings, replace the complete as- sembly, as the air regulator is nonserviceable.
4. CONTROL VALVE (See Pages 28 and 29.) With the gear shift lever in neutral, select HIGH RANGE and disconnect the 1/8" O.D. air line at the OUTLET or “P” Port of control valve.