Air System Symptom - No or Slow Range Shift into Low (Shift into High is Good)
Test Procedures:
Test Procedures:
1.
1.Check the Shift Knob operation.
On the Shift Knob, remove the two screws holding the Plastic Skirt. Slide the Skirt down and out of the way. Move the Range Selector up into High Range. Disconnect the black line connected to the “P” port on the Knob. Move the Range Selector down into Low. Answer the question on the chart below and follow the instructions corresponding to the result:
2.
2.Check the air supply to the Shift Knob.
Disconnect the red line from the “S” port on the Shift Knob. Answer the question on the chart below and follow the instructions corresponding to the result:
3.
3.Check the black line for obstruction.
Reconnect the black line at the Shift Knob. At the Air Module, disconnect the black air line from the “P” port. Answer the question on the chart below and follow the instructions corresponding to the result:
Q
Quueessttiioonn RReessuulltt WWhhaat tto ddo o NNet o exxtt Does air come out of the “P” port on the
Knob?
Yes Step Go to 3.
No Reconnect the Air Line to the Knob, and
continue to the next Step.
Q
Quueessttiioonn RReessuulltt WWhhaat tto ddo o NNet o exxtt Is air coming out of the red line? Yes Repair or replace the Shift Knob.
No Loosen the air fitting for the line that
supplies vehicle air to the Module Inlet. If no air is available here, repair the vehicle air to the Air Module. If air is available at the Inlet, check the red line going from the Air Module to the Shift Knob for obstructions or damage. If the line is clear, replace the Air Module.
Q
Quueessttiioonn RReessuulltt WWhhaat tto ddo o NNet o exxtt Is air available on the line when the
Range Selector is in the Low position?
Yes Continue to next Step.
No Repair the black line for damage or
obstruction.
Air System Troubleshooting
4.4. Check the Regulator pressure.
Reconnect the “P” line at the Air Module. Locate the two small Pipe Plugs on the rear of the Air Module. One is labeled “H,” and the other is labeled “L”. (See Figure 4-1 “Air System Nomenclature”). Install a 0–150 PSI (0–1034 kPa) Air Gauge in the port marked “L”.
Note:
Note:Prior to removing the Pipe Plug, turn off the air flow by placing the Range Selector up into the High Range position. The Transmission must be in Neutral.
Move the Range Selector down to the Low position and record the pressure on the Gauge. Match the air pressure to one of those described on the chart on the next page, and follow the corresponding instructions:
Q
Quueessttiioonn RReessuulltt WWhhaat tto ddo o NNet o exxtt What is the air pressure at the “L” port? 75–85 PSI (517–586 kPa)
(To specification.)
Continue to the next Step.
Less than 75 PSI (517 kPa) Warning:Warning: The Pipe Plug to be removed in this procedure is pressurized and could be expelled with great force. To prevent personal injury or damage to parts, exhaust the Air Module before removing the plug, and repressurize the Air Module after installing the Gauge
On the top or the Air Module, remove the Test Port Pipe Plug for filtered vehicle air.
(Marked “F” as shown in figure 4-1 “Air System Nomenclature”).
Install the Test Gauge in the “F” port, and check the pressure. If the pressure is less than 90 PSI (620 kPa), repair the Vehicle Air System to achieve full vehicle air pressure at the Module Inlet, and repeat the test. If the pressure is greater than 90 PSI (620spa) and no external air leaks were detected form the Air Module, Shift Knob, or Transmission, replace the Air Module.
Greater than 85 PSI (586 kPa) Replace the Air Module.
Air System Troubleshooting
6.6. Isolate the Air Module from the Transmission. Refer to Figure 4-4 “Air System Nomenclature” to see an example of an isolated Air Module.
Failure to exhaust the Air Module may cause personal injury or damage to parts due to the rapid release of air.
Failure to exhaust the Air Module may cause personal injury or damage to parts due to the rapid release of air.
Exhaust the air pressure from the Air Module. To do so, you may have to exhaust the vehicle air. Remove the four capscrews attaching the Air Module to the Shift Bar Housing. Lift the Air Module and tilt it to gain access to the two air holes on the underside at the rear capscrew location. Do not lose or damage the two small O-rings that seal the holes. Block off the air ports at the underside of the module. Repressurize the Air Module with an inlet supply pressure of over 90 PSI (620 kPa). To repressurize the Air Module, the vehicle may have to be started and the air pressure allowed to build. With the Shift Lever in Neutral and the Gauge still in the “L” Test Port, move the Range Selector from Low to High (up) position.
Answer the question on the chart below, and follow the corresponding instructions:
7.7. Install the Air Module, and remove Range Alignment Lock Cover (Figure 4-4 “Air System Nomenclature”). Then move the Range Selector from Low to High (up) position. If range now shifts properly, inspect and correct source of binding between Lock Cover and Range Yoke Bar.
NOTE:
NOTE: To prevent binding, Range alignment Lock Cover Capscrew must be tighten when Transmission is in Low Range.
If Transmission does not shift properly, continue to Step 8.
8.
8.Remove the Auxiliary Section, and inspect Range Synchronizer, Range Yoke, Range Yoke Bar, Range Yoke Snap Rings, Range Sliding Clutch, and mating gears for excessive wear, binding, or damage. Repair as necessary. If these components do not need repair, continue to Step 9.
9.
9.Remove Shift Bar Housing and inspect Range Piston, Piston Bar, and Cylinder for excessive wear, binding, or damage. Repair as necessary.
Q
Quueessttiioonn RReessuulltt WWhhaat tto ddo o NNet o exxtt Does the Gauge rapidly go from
75–85PSI (517–586 kPa) in Low to 0 PSI in High
Yes Continue to next Step.
No Replace the Air Module.
WARNING
Air System Troubleshooting
G e n e r a l I n f o r m a t i o n