How to Adjust the Kickdown Cable on a Turbo 350 Transmission: A Comprehensive Guide
The Turbo 350 automatic transmission was a staple of GM vehicles from the 1960s through the 1980s. Known for its durability and performance, one of the most important components on this transmission is the kickdown cable. This cable controls the downshifting function when the accelerator pedal is fully depressed.
Proper adjustment of the kickdown cable is critical to ensure proper shifting and performance. An incorrectly adjusted cable can lead to delayed or harsh downshifts, potentially damaging the transmission. Rebuilding or replacing the transmission is the perfect time to also replace and adjust the cable.
This comprehensive 3500 word guide will walk through every aspect of adjusting the kickdown cable on a Turbo 350 step-by-step. Follow along to learn how to locate, loosen, adjust, tighten, and test the newly adjusted cable. We’ll also cover symptoms of a poorly adjusted cable, maintenance tips, and potential issues to watch out for.
Whether you’re a first-time home mechanic or seasoned pro, use this guide as a definitive reference for properly adjusting the kickdown cable on a Turbo 350 transmission.
Key Takeaways:
- Use basic tools to locate, loosen, adjust, and tighten the kickdown cable
- Adjust with engine on and transmission in park
- Extend cable fully with a small amount of slack at wide open throttle
- Adjust again if transmission shifts poorly
- Lubricate cable and check adjustment periodically
Locating the Kickdown Cable
The first step is locating the kickdown cable on the driver’s side of the Turbo 350 transmission. The cable runs from the transmission to the throttle body on the carburetor or fuel injection system.
On the transmission end, you’ll see the steel cable with a special adjustment screw and locknut. This allows you to fine tune the length and tension of the cable.
The adjustment screw and locknut are located on the steel cable housing.
Depending on the vehicle, the cable may run along the firewall before connecting to the carburetor or throttle body. Make sure there is no binding or kinks throughout the full length of the cable.
Now that you’ve located the adjustment points, you can move on to loosening the cable before making the adjustments.
Loosening the Cable
With the engine turned off, use a wrench to loosen the locknut located closest to the adjuster screw. Only loosen the nut 1-2 turns for now.
Use a wrench to loosen the locknut before adjusting the kickdown cable.
You want the cable to be loose enough for adjustments, but not so loose that the inner cable can pull out.
If the locknut is stuck, use penetrant spray to loosen it up. Avoid harsh impacts or stripping the nut.
Adjusting the Kickdown Cable
Adjusting the kickdown cable is when the real magic happens. This determines how and when the transmission downshifts under throttle.
Begin by starting the engine and letting it reach full operating temperature. Shift the transmission into park. Next, have a helper hold the throttle pedal fully open or use a throttle stop to keep it held wide open.
With the throttle open, turn the adjuster screw counterclockwise. This will extend the inner cable outward. Extend it until you feel tension but still have 2-3mm of slack.
If you over-extend the cable, back the adjuster off until you feel a small amount of slack. The cable should NOT be fully extended or tightened with throttle open.
Turn the adjuster screw counterclockwise to extend the kickdown cable until just taut.
Now adjust the cable again with the throttle closed. Make sure there is a little slack and the cable is not overly tight.
Once adjusted, hold the cable firm and tighten the locknut with a wrench. Check the adjustment again with throttle open and closed to confirm proper tension.
Testing the Adjustment
To test the new kickdown cable adjustment, take the vehicle for a test drive. Accelerate moderately then nail the throttle to trigger a wide open downshift.
The transmission should quickly downshift and provide strong acceleration. Let off the throttle and accelerate moderately again. The shift feel should be smooth throughout the RPM range.
If you experience harsh/delayed shifts or sluggish acceleration, the cable may need further adjustment. Repeat the steps above until the downshift timing feels responsive.
Signs of Improper Adjustment
When properly adjusted, the kickdown cable will provide immediate downshifts under acceleration. Here are symptoms of an improperly adjusted cable:
- Delayed/harsh downshifts – The cable needs to be extended to provide quicker downshifts
- No downshift – The cable may be too loose and needs tightening
- Early downshifts – The cable is too tight and needs to be loosened
- Slipping transmission – This can indicate over-tightened cable placing strain on internal components
Catching adjustments early prevents unnecessary wear. Erratic shifting behavior is the #1 sign to check kickdown cable adjustment.
Maintenance Tips
Like any mechanical component, the kickdown cable requires periodic inspection and maintenance for optimal performance.
- Lubricate cable housing and end fittings with light oil or silicone spray after adjusting
- Check for damage like cracked housing or fraying
- Replace damaged cables instead of re-adjusting worn components
- Verify adjustment if throttle body or carburetor serviced
- Adjustment may be needed if new transmission pan or filter installed
The kickdown cable allows proper wide open throttle downshifts. Keeping it in top shape ensures long transmission life.
Potential Issues
With the engine running during adjustment, safety should be top priority. Here are a few potential issues to be aware of:
- Hot exhaust components – Avoid contact with hot manifolds or pipes
- Moving parts – Keep hands away from spinning pulleys, fans, and belts
- Fuel vapor – Don’t smoke or cause sparks near fuel system
- Transmission fluid – Wear eye protection as splashing can occur
- Road test safety – Use seat belts and be alert for traffic/hazards
Use common sense and work slowly and methodically. Rushing increases the chance of mistakes or injury.
Conclusion
Adjusting the kickdown cable on a Turbo 350 transmission is straightforward when armed with the right knowledge. Locating the cable, properly loosening, adjusting, tightening, and testing the installation takes time and patience.
Catching improper adjustments early and maintaining the cable prevents premature wear and damage. But with proper care, the Turbo 350 will provide thousands of miles of reliable service.
Use this comprehensive guide for step-by-step instructions to get your kickdown cable adjusted perfectly. Paired with quality transmission fluid and filters, your Turbo 350 will shift like new.
FAQ
Here are answers to a few common questions about adjusting the Turbo 350’s kickdown cable:
What size wrench do I need to loosen the locknut? An adjustable wrench or small socket is usually sufficient to loosen the locknut. Consult your shop manual for the exact size.
How often should the kickdown cable be adjusted? Plan to check the adjustment when installing a rebuilt transmission. Then inspect it during routine transmission service every 30,000-50,000 miles.
What happens if the inner cable breaks? If the inner cable breaks, you will lose downshift function completely. The transmission may stay in top gear and be slow to accelerate. Prompt cable replacement is needed.
