GM Full-Size Trucks 1988-1998 Repair Information

Adjustments

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Shift Linkage

See Figures 1, 2, 3 and 4

  1. Raise and support the front end on jackstands. Block the rear wheels.
  2.  



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Fig. Fig. 1: Shift linkage-THM 400 and THM 700R4 transmissions



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Fig. Fig. 2: Shift positions-THM 400 and THM 700R4 transmissions



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Fig. Fig. 3: Shift linkage-4L60E and 4L80E transmissions



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Fig. Fig. 4: Shift positions-4L60E and 4L80E transmissions

  1. Loosen the shift lever bolt or nut at the transmission lever so that the lever is free to move on the rod.
  2.  
  3. Set the column shift lever to the neutral gate notch, by rotating it until the shift lever drops into the Neutral gate. Do not use the indicator pointer as a reference to position the shift lever, as this will not be accurate.
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  5. Set the transmission lever in the neutral position by moving it clockwise to the park detent, then counterclockwise 2 detents to neutral.
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  7. Hold the rod tightly in the swivel and tighten the nut or bolt to 17 ft. lbs. (23 Nm) on all but the 4L80E transmission. On the 4L80E transmission, tighten the bolt to 20 ft. lbs. (30 Nm).
  8.  
  9. Lower the vehicle.
  10.  
  11. Move the column shifter to park and check that the engine starts. Check the adjustment by moving the selector to each gear position.
  12.  

Shift Cable

This procedure applies to 4L60-E and 4L80-E transmissions.

  1. Place the transmission in park and apply the parking brake.
  2.  
  3. Raise and support the vehicle on jackstands.
  4.  
  5. On the shift cable end slide the black retaining clip forward just enough to allow the white lock button to be out.
  6.  

Do not push the white lock button completely out.

  1. Push the white lock button out just far enough to free the metal core adjust body inside the core.
  2.  
  3. Inspect the core adjust body for dirt or debris that may restrict its travel.
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  5. If there are any restrictions found the shift cable end should be washed with soap and water. If after cleaning the cable the travel of the core adjust body is still restricted the shift cable assembly must be replaced.
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  7. Lower the vehicle, turn the ignition switch ON and move the transmission lever from park to one-to-ten times.
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  9. Place the shift lever in park and turn the ignition switch OFF . Raise and support the vehicle on jackstands.
  10.  
  11. Make sure the transmission is in mechanical park by rotating the control lever clockwise until it stops.
  12.  
  13. Push the white lock button in to secure the core adjuster body adjuster and slide the black retainer clip rearward until it covers the white lock button and locks in place over the shift cable end.
  14.  
  15. Lower the vehicle and turn the ignition switch ON .
  16.  
  17. Move the shifter through the gear ranges and ensure that the light comes on under the shift column letter when the shifter is positioned under that letter.
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  19. Ensure that the engine starts only when the transmission is placed in park or neutral. Adjust the park/neutral switch if necessary. Refer to the park/neutral switch adjustment procedure in this section.
  20.  
  21. Turn the ignition switch to the LOCK position and ensure that the key can be removed in the park position only.
  22.  
  23. Release the parking brake, start the engine and check for proper transmission shift operation.
  24.  

Throttle Valve Cable

This procedure applies to the THM 700R4 transmission.

The adjustment is made at the engine end of the cable with the engine off, by rotating the throttle lever by hand. DO NOT use the accelerator pedal to rotate the throttle lever.

  1. Remove the air cleaner.
  2.  
  3. Depress and hold down the metal adjusting tab at the end of the cable.
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  5. Move the slider until it stops against the fitting.
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  7. Release the adjusting tab.
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  9. Rotate the throttle lever to the full extent of it travel.
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  11. The slider must move towards the lever when the lever is at full travel. Make sure that the cable moves freely.
  12.  

The cable may appear to function properly with the engine cold. Recheck it with the engine hot.

  1. Road test the truck.
  2.  

Neutral Start/Back-Up Switch

The procedure is for switches that are mounted on the transmission only.

This adjustment is performed with the switch removed from the vehicle. Neutral position tool J 41364-A or its equivalent is required for this procedure.

  1. Position tool J 41364-A or its equivalent onto the park/neutral switch. make sure that the slots on the switch are lined up with the lower tabs on the tool.
  2.  
  3. Rotate the tool until the upper locator pin on the tool is lined with the slot on the top of the switch.
  4.  

Do not remove the tool from the switch.

  1. Install the switch and remove the tool.
  2.  

 
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