Important Safety Note: Before working under your car, make sure it's securely supported on jack stands, not just a jack. Never work under a car supported only by a jack.
1. Locate the Parking Brake Cable Adjusters: At each rear wheel, you'll find a small, usually star-shaped adjuster nut on the parking brake cable. This nut is connected to the brake cable mechanism that operates the shoes within the drum brake. It's usually located near the backing plate of the brake drum, and may be difficult to see until the wheel is removed.
2. Remove the Rear Wheels: This is essential for access to the adjusters. Loosen the lug nuts before jacking up the car and removing the wheels.
3. Locate the Adjuster: With the wheel off, you should clearly see the adjuster. It might be covered in dust and grime.
4. Adjust the Cable: Using a wrench or socket that fits the star-shaped adjuster nut (size varies, so check beforehand), *very slowly* turn the adjuster nut. Turning the nut clockwise tightens the cable and increases the parking brake's effectiveness. Turning it counter-clockwise loosens the cable.
5. Test and Adjust: After a few turns, carefully engage the parking brake. Check how much slack there is in the cable and how firmly the brake holds. If it still has excessive slack, continue adjusting, but only a little at a time. Repeat this process until you have a good firm hold and the lever has about 3-4 clicks before it stops. Overtightening can cause the brakes to drag when driving.
6. Reassemble: Once you're satisfied with the adjustment, reinstall the wheels and lower the car.
7. Final Test: Test the parking brake thoroughly on a level surface to ensure adequate holding power but no dragging.
Important Considerations:
* Even Adjustment: Make sure you adjust both rear brakes equally to prevent uneven braking.
* Brake Drum Condition: If your parking brake is consistently ineffective, it may be a sign of worn-out brake shoes or other issues within the brake drum assembly. The adjusters will only work if the mechanical linkage within the drums are in good condition.
* Cable Condition: A frayed, broken, or severely corroded cable may require replacement, rather than simply adjusting. If you find the cable is damaged, replacing it is crucial.
* Manual: A 1968 GTO shop manual will provide illustrations and specifications that will make the job significantly easier and safer.
If you're not comfortable working on your brakes, it's always best to take your car to a qualified mechanic. Brake adjustments that are not performed correctly can be dangerous.
