ronjenx

I have been wondering how the parking brake lever works.
People have had it fail, and it was not clear to me what failed.
This is how it works:

1. Here is an overview of the passenger side of the parking brake lever assembly.
The pin which loops over the black lever is installed to keep the tension spring from unwinding. It is removed after the cables are connected.




2. Here is an overview of the driver's side of the parking brake lever assembly.





3. A more detailed view of the various parts.
The tension spring is attached to the cable drum.
It keeps about 20 pounds pull on the cable when the parking brake is released. This removes the slack from the system.
The cable drum is made from two pieces, with one piece extending under the clutch spring.
The clutch spring is wound around the drum tightly enough to be a friction fit on the drum.
One end of the clutch spring extends from the bottom of the spring, and is anchored to the parking brake lever.
Lifting the lever causes the clutch spring to wind even more tightly around the drum, so the drum rotates with the lever, which pulls on the brake cable.






4. As the lever is pulled up, the clutch spring, being anchored to the lever, rotates, tightening itself on the drum.
This drags the drum around with it, pulling the cable.
The clutch spring tail moves away from the stop, which is actually the thing that allows the clutch spring to wind itself tighter on the drum.






5. Here the lever has been raised as if to apply the parking brake.
The spring clutch tail has also rotated away from the stop.
If you were to pull on the tail, toward the camera, it would unwind the clutch spring, making its diameter bigger, thereby releasing the cable drum. The lever position would not change, though. It would move freely as long as you followed the rotation with the spring tail.
When the lever is returned to the down position, the clutch spring tail also rotates toward the stop. It hits the stop just before the lever bottoms out. This releases the clutch spring, and the tension spring is free to rotate the cable drum, maintaining 20 pounds tension on the cable.






6. Here you see what breaks when you go to apply the parking brake, and hear a loud SNAP!
The lever will then be free to move, and no torque will be applied to the cable drum.


An ineffective parking brake could be caused by any one of several things:
Worn shoes
Shoes out of adjustment
Broken cable(s)
Broken clutch spring arm
Slipping clutch spring
Broken tension spring

dmhines

Is there a way to adjust the engagement? I gotta yank the he'll out of mine to hold my JK on an incline.

kingteddybear

Once again a great job!

ronjenx

Thanks!
.....

GoodysGotaCuda

good info, proving furthermore Jeep cheaped out everywhere they could on the JK!

ronjenx

I think a simple cable drum riveted to the lever would have been cheaper.

I think this is an effort to eliminate slack in the cables, and to give the lever a new bite on the primary cable each time the lever is pulled up.
The weak link is the thin clutch spring arm.

kashlak

Don't yank it to hard the whole damn brake will snap. Just happened to me. Mine always drifted in my driveway so yes I had to yank the crap out of it to stay in one place. Being my husband just had ACL surgery I had to take it to the stealership. I pick it up tonight $275 later

Smopho

Yes, back up slowly and pull up on the lever. Repeat several times until the slack is taken up. The rear parking brake shoes will self adjust out to compensate for wear.

Granger

I have replaced the shoes and everything and still doesn't engage like it's supposed to. I will try the reverse technique and get back when I figure out if it did anything.

ronjenx

This will not make the shoes self-adjust. There is no mechanism in place to accomplish that.

At best, it equalizes the cables, making the parking brake a little more effective. It won't work if the lever needs to be pulled way up. In that case, the shoes need to be manually adjusted.