1. Safety First:
* Disconnect the negative battery terminal. This prevents accidental short circuits.
* Engage the parking brake. Absolutely crucial.
2. Locate the Cable:
* The kickdown cable connects from the carburetor (or throttle body if you have a later carburetion system with a throttle body added) to the transmission. Trace the cable to find both ends.
3. Disconnect the Cable:
* At the Transmission: There's usually a clevis or a clamp securing the cable to the transmission linkage. You'll likely need a small screwdriver or pliers to release this connection. Take a picture or make a note of how it's connected before disconnecting.
* At the Carburetor/Throttle Body: This end is usually attached via a similar clevis or clamp to a lever or bracket on the carburetor. Again, carefully disconnect it and note its position.
4. Remove the Old Cable:
* Gently pull the old cable out of its routing. Note how it is routed; there may be clips or brackets holding it in place. You'll need to replace it along the same path with the new cable.
5. Install the New Cable:
* Feed the new cable through the same route as the old one. Make sure it's properly seated in any clips or brackets.
* Connect the new cable to the transmission. Use the picture or notes you made earlier to ensure correct re-attachment.
* Connect the new cable to the carburetor/throttle body. Again, carefully align it as it was previously attached.
6. Adjust the Cable:
* This is the most crucial step. Improper adjustment will result in poor shifting and can damage the transmission. There are generally two methods for adjustment:
* Manual Adjustment: Many systems have a threaded adjuster on the cable itself (usually near the transmission end). You'll need to make small adjustments, shifting the transmission through the gears while monitoring the kickdown cable's position. The goal is to have the cable slightly slack when the throttle is closed and fully extended when the throttle is fully open (in 1st gear). Consult a repair manual for specifics.
* Automatic Adjuster: Some vehicles have an automatic adjuster built into the cable or bracket at the transmission. If present, follow the instructions for adjusting this.
7. Test the Adjustment:
* Start the engine and carefully shift the transmission through the gears, paying close attention to how the kickdown cable operates. If the shifting is harsh or lacks firmness, you'll need to readjust the cable. You may need to repeat this process several times.
8. Reconnect the Battery:
* Once you're satisfied with the adjustment, reconnect the negative battery terminal.
Important Notes:
* Repair Manual: A repair manual specific to your 1972 Chevrolet C20 is invaluable. It will provide detailed diagrams and instructions for your specific model.
* Cable Length: Ensure you purchase a replacement cable of the correct length. Using a cable that is too long or too short will prevent proper adjustment.
* Patience: Take your time; rushing this process can lead to mistakes. Be methodical and double-check your work at each step.
If you're uncomfortable performing this repair yourself, it's best to take your truck to a qualified mechanic. Improper adjustment can damage your transmission.
