C4 and C6 Transmissions
- Raise and support the van on jackstands.
- Clean all dirt away from the band adjusting screw. Remove and discard the locknut.
- Install a new locknut loosely and tighten the adjusting screw to 10 ft. lbs. (13.6 Nm).
- Back off the adjusting screw EXACTLY 1 3 / 4 turns for the C4, or 1 1 / 2 turns for the C6.
- Hold the adjusting screw from turning and tighten the locknut to 35-40 ft. lbs. (47-54 Nm).
- Remove the jackstands and lower the vehicle.
REAR BAND (LOW/REVERSE)
C4 Transmissions Only
- Clean all dirt from around the band adjusting screw and remove and discard the locknut.
- Install a new locknut on the adjusting screw. Using a torque wrench, tighten the adjusting screw to 10 ft. lbs. (13.6 Nm).
- Back off the adjusting screw EXACTLY 3 FULL TURNS.
- Hold the adjusting screw steady and tighten the locknut to 35-45 ft. lbs. (47-61 Nm).
- With the engine stopped, place the transmission selector lever at the steering column in the N (neutral) position for models through 1967, or the D (drive) for 1969 and C4 and C6 later models. On the later C4 and C6 models, make sure the lever is against the D stop. On AOD models, place the lever in the Overdrive position.
- Loosen the shift rod adjusting nut at the transmission lever.
- On models through 1967, place the transmission lever in the N position (4th detent from the rear). On all other models, place the transmission lever in the 2nd detent from the rear.
- On models through 1967, insert a 1 / 4 in. gauge pin through the steering column shift rod actuating lever and the steering column shift tube bracket to hold the shift rod linkage in the N position.
- On 1974 and later models: With the selector lever and transmission manual lever in the required position, turn the trunnion so that it slips into the hole in the transmission lever and tighten the adjusting nut to 12-18 ft. lbs. (16-24 Nm). Do not allow the rod or shift lever to move while tightening the nut.
- On models through 1967, turn the trunnion 1 full turn counterclockwise to lengthen the rod. Connect the trunnion to the lever. Remove the gauge pin.
- On 1969-71 models, turn the trunnion 4 full turns counterclockwise to lengthen the rod. Connect the trunnion to the lever.
- On 1972-73 models, lock the trunnion without turning it. Connect the trunnion to the lever.
- Check the operation of the shift linkage.
THROTTLE VALVE LINKAGE
ADJUSTMENT AT THE CARBURETOR
The TV control linkage may be adjusted at the carburetor using the following procedure:
- Check that the engine idle speed is set to specification. Turn off the engine.
- De-cam the fast idle cam on the carburetor so that the throttle lever is at its idle stop. Place the shift lever in N (neutral), set the parking brake.
- Back out the linkage lever adjusting screw all the way. The screw end should be flush with the lever face.
- Turn in the adjusting screw until a thin shim (0.005 in. max.) or piece of writing paper fits snugly between the end of the screw and the throttle lever. To eliminate the effects of friction, push the linkage lever forward (tending to close gap) and release it, before checking the clearance between the end of the screw and the throttle lever. Do not apply any load on the levers with tools or hands while checking the gap.
- Turn in the adjusting screw an additional 4 turns. (Four turns are preferred. Two turns minimum are permissible if the screw travel is limited).
- If it is not possible to turn in the adjusting screw at least two addition turns or if there was sufficient screw adjusting capacity to obtain an initial gap in Step 2 above, refer to Linkage Adjustment at Transmission. Whenever it is required to adjust the idle speed by more than 50 rpm, the adjustment screw on the linkage lever at the carburetor should also be readjusted as shown.
Idle Speed Change/Turns on Linkage Lever Adjustment Screw
After making any idle speed adjustments, always verify that the linkage lever and throttle lever are in contact with the throttle lever at its idle stop and the shift lever is in N (neutral).ADJUSTMENT AT THE TRANSMISSION
The linkage lever adjustment screw has limited adjustment capability. If it is not possible to adjust the TV linkage using this screw, the length of the TV control rod assembly must be readjusted using the following procedure. This procedure must also be followed whenever a new TV control rod assembly is installed.
This procedure requires placing the vehicle on jackstands to give access to the linkage components at the transmission TV control lever.
- Set the engine curb idle speed to specification.
- With the engine off, de-cam the fast idle cam on the carburetor so that the throttle lever is against the idle stop. Place the shift lever in N and set the parking brake.
- Set the linkage lever adjustment screw at its approximate mid-range.
- If a new TV control rod assembly is being installed, connect the rod to the linkage lever at the carburetor.
- Raise and support the van on jackstands.
- Using a 13mm box end wrench, loosen the bolt on the sliding trunnion block on the TV control rod assembly. Remove any corrosion from the control rod and free-up the trunnion block so that it slides freely on the control rod. Insert a pin into the transmission lever grommet.
- Push up on the lower end of the control rod to insure that the linkage lever at carburetor is firmly against the throttle lever. Release the force on rod. The rod must stay up.
- Push the TV control lever on the transmission up against its internal stop with a firm force (approximately 5 pounds) and tighten the bolt on the trunnion block. Do not relax the force on the lever until the nut is tightened.
- Lower the vehicle and verify that the throttle lever is still against the idle stop. If not, repeat Steps 2 through 9.
THROTTLE KICKDOWN LINKAGE
- Move the carburetor throttle linkage to the wide open position.
- Insert a 0.060 in. thick spacer between the throttle lever and the kickdown adjusting screw.
- Rotate the transmission kickdown lever until the lever engages the transmission internal stop. Do not use the kickdown rod to turn the transmission lever.
- Turn the adjusting screw until it contacts the 0.060 in. spacer.
- Remove the spacer.