Parking Brake control module

[Larryjb]

(control module, that's what they call it in the service manual)

I'm used to these parking brakes ratcheting as you depress them. Were they supposed to ratchet in 2002?

The cable between the release handle and parking brake module has broken. I'm trying to decide whether to replace the entire module (about $50 for ACDelco), or just the handle/cable (so far, about $20). It's not much more for the entire module, but it's a fair bit more work to do the module than just the release cable.

I'm also not convinced the autoadjust mechanism has been working, but I've read that sometimes it needs to be reset. I did have to replace my intermediate cable a couple of years ago.

 

[OR VietVet]

On my 2002 there is no ratcheting. I would just do the handle and cable. The shoes for the park brake can be adjusted after pulling the rear rotors but they hardly ever need adjustment unless you accidentally drive with the park brake on. The adjusting mechanism can bind or freeze up with age as well or rust. I recently did mine. It was not that much work and I did rear pads at the same time.

 

[Larryjb]

Thanks Ron,

I had adjusted the rear parking shoes so that I could just slip the rotor back on. I also removed the rust ridge with a file. As a result, the parking brake did work, but the pedal would go to the floor so I don't think something was done right.

As I said in my original post, I had replaced my intermediate cable because it broke. However, I also suspect that I didn't set up the autoadjuster correctly at the time and I'm now thinking that's why my pedal was going to the floor.

Is there any chance I wrecked the auto adjuster? Do I just need to set it up again? The service manual says to pump the parking brake 3 times until it auto adjusts, but that didn't work either.

 

[OR VietVet]

The auto adjuster will be in with the shoes, like the self adjuster for rear brake shoes would be. Will look like this: https://www.rockauto.com/en/moreinfo.php?pk=904564&cc=1380372&jsn=2266&jsn=2266


When you filed the rust ridge and installed the rotor there seems to still be too much travel before the shoes contact inside at the rear rotor/drum combination.

You could have that little drum section machined and clean the shoes and make sure the adjuster is free and lubed and then get a tighter fit.

 

[Larryjb]

Our parking brake modules have an auto adjust for pedal height as well as the adjuster at each wheel. It is meant to take up some of the cable slack. I don't think many DIY know about it unless they have and read the FSM for the parking brake.

 

[OR VietVet]

I would almost bet that the adjustment for pedal height and at each wheel is just a fine tune adjustment, so to speak. The initial main adjustment needs to be done at the adjusters at the rear park brake shoes. I could be wrong but I am going to stick with my gut feeling on this.

 

[swathdiver]

Thanks Ron,

I had adjusted the rear parking shoes so that I could just slip the rotor back on. I also removed the rust ridge with a file. As a result, the parking brake did work, but the pedal would go to the floor so I don't think something was done right.

As I said in my original post, I had replaced my intermediate cable because it broke. However, I also suspect that I didn't set up the autoadjuster correctly at the time and I'm now thinking that's why my pedal was going to the floor.

Is there any chance I wrecked the auto adjuster? Do I just need to set it up again? The service manual says to pump the parking brake 3 times until it auto adjusts, but that didn't work either.

Sounds like you did what I did. Before working on the shoes out back, did you disable the parking brake actuator? We're supposed to pull the foot pedal all the way up and insert a screwdriver into a hole in the side of the unit while someone else pulls the main cable underneath the truck rearward so the holes line up for the screwdriver. I didn't know how to do this. My parking brake holds but goes mostly to the floor with new shoes.

Speaking of shoes, you know how much clearance is supposed to be between the shoe and drum? A quarter of a millimeter! I bought a brake shoe caliper to measure mine. I need to take it all apart and reset everything proper too. Come on over to my house and we'll get it done!

 

[Larryjb]

I had already adjusted the main adjustment at the wheels tight enough that I could barely get the disk back on. I did the same method on my wife's Explorer and the pedal is firm and very little travel in the parking brake pedal. In my Tahoe, the pedal would go straight to the floor before the brake would hold. It's my understanding that most of my pedal travel has been taking up slack in the cable.

I will take a closer look this weekend at the mechanism, if possible. I understand that it is possible that the autoadjuster is disabled:
https://www.gm-trucks.com/forums/topic/97978-parking-brake-adjustment/

 

[swathdiver]

I had already adjusted the main adjustment at the wheels tight enough that I could barely get the disk back on. I did the same method on my wife's Explorer and the pedal is firm and very little travel in the parking brake pedal. In my Tahoe, the pedal would go straight to the floor before the brake would hold. It's my understanding that most of my pedal travel has been taking up slack in the cable.

I will take a closer look this weekend at the mechanism, if possible. I understand that it is possible that the autoadjuster is disabled:
https://www.gm-trucks.com/forums/topic/97978-parking-brake-adjustment/

There's another thread over there with pictures, again a guy with a Duramax doing the job. For some reason, it's been very difficult for my brain to understand how to do this properly!

 

[Larryjb]

Sounds like you did what I did. Before working on the shoes out back, did you disable the parking brake actuator? We're supposed to pull the foot pedal all the way up and insert a screwdriver into a hole in the side of the unit while someone else pulls the main cable underneath the truck rearward so the holes line up for the screwdriver. I didn't know how to do this. My parking brake holds but goes mostly to the floor with new shoes.

Speaking of shoes, you know how much clearance is supposed to be between the shoe and drum? A quarter of a millimeter! I bought a brake shoe caliper to measure mine. I need to take it all apart and reset everything proper too. Come on over to my house and we'll get it done!

James,

I'm starting to understand now, I think.

When doing the shoes, they need to be adjusted to spec as you say. However, if you do a complete job by replacing the adjuster in the wheel, removing the actuator the connects the cable to the adjuster, you will have to introduce slack into the cable to get it hooked back up again. When you get everything put back together, even if the parking brake shoes are adjusted right, there will still be slack in the cable that is very difficult to remove. Even if you tighten things up at the equalizer, you may not be able to tighten it correctly.

By releasing the tension at the pedal by inserting the screwdriver, you can do all the work in the back without undoing the equalizer. Then once you have everything done in the back, making the sure equalizer is tightened to the specified torque, the autoadjuster will remove the remaining slack in the cable.

I'll look for the other thread you mentioned.

 

[Larryjb]

There's another thread over there with pictures, again a guy with a Duramax doing the job. For some reason, it's been very difficult for my brain to understand how to do this properly!

"Like hand grenade out of frustration"? I love that quote. Thanks, I needed the laugh!

 

[Larryjb]

Now I know why my parking brake release cable broke. Some one pulled the pin on the grenade!

All kidding aside, once I install the new release cable, I'll see about adjusting the nut on the equalizer better. I don't think I have it tightened properly.

 

[Larryjb]

Here's a summary of a parking brake adjustment procedure from Autozone that may help. It appears to be one of the best procedures I've come across. However, I haven't tried it yet.

Some differences between this and the factory service manual:
Steps 4-6 never appears in the factory service manual.
Step 7: Factory service manual states to tighten the nut to 31 lb in. I could never figure this out. With a little dirt and corrosion on the thread, you could easily get 31 lb in and not have the the nut tightened properly.

I have no idea if this procedure will work. It may be a hack, it may bypass the auto-adjustment mechanism for pedal height. I'm just putting this out there. I may try this in a few weeks.

1. The parking brake must be adjusted any time the parking brake cables are serviced, or the holding ability is not adequate. Before adjusting the parking brake, check the condition of the service brakes. The service brakes must be adjusted properly before adjusting the parking brake.
   
2. Raise the vehicle and support the vehicle with safety stands.
   
3. Loosen the adjusting nut at the equalizer.
   
4. Set the parking brake by pushing the pedal down 18 degrees.
   
   
   Fig. Locating hole in park brake pedal assembly
   
   
   
5. Insert a 0.125 in. (3 mm) pin into locating hole in the pedal assembly.
   
6. Push the pedal downward until the pin contacts the parking brake outer flange.
   
7. Turn the adjusting nut at the equalizer until the wheels rotate forward with a moderate drag.
   
8. Release the parking brake, remove pin and rotate the rear wheels. There should be no drag.
   
9. Lower the vehicle.

 

[OR VietVet]

So, I gotta use an angle gauge to do the 18 degree set and adjust the parking brake? C'mon man! Surely the person that came up with that procedure could have given more "real world" instructions. But, if it works, it works.

 

[Larryjb]

Great, a day after ordering the parking brake release handle from Amazon, I find a crack in the actual parking brake module. Hopefully Amazon will allow the cancellation of the handle, especially now that I've ordered the entire module.

Maybe this is why the auto-adjuster never adjusted the pedal height.

 

[OR VietVet]

All, you have to do is send back the release handle and they will credit it. Typically a cancellation will not be allowed if enough time goes by, like maybe 6 hours after the order. But send it back and they ask for why you are sending it back and just explain that you ordered the whole assembly and explain why. I have never had any problems sending things back to Amazon.

Hell, I have even been given a choice of keeping the item for free or sending back because the cost is minimal for them to give for free instead of eating the return shipping charges.

 

[Larryjb]

Here's a picture of the module. I had no idea it was cracked. You may wish to check yours, especially if your pedal goes to the floor like mine was.

I apologize for the quality. I am still using a 7 year old Blackberry (and still loving it). (If I really need good pictures I'll get out the SLR.)

 

[swathdiver]

Great, a day after ordering the parking brake release handle from Amazon, I find a crack in the actual parking brake module. Hopefully Amazon will allow the cancellation of the handle, especially now that I've ordered the entire module.

Maybe this is why the auto-adjuster never adjusted the pedal height.

Got a picture? Maybe mine is the same way.

I was wanting to change mine to the JNC, push to release actuator, that was an option on the 900s and standard in our Pontiacs. It has a different actuator of course but also the three cables are all different too. Costs about $125 to do the swap in parts without getting a new knee bolster. I would just RTV the brake release in place.

 

[Larryjb]

Hmmm, this got moved to Engine and Drivetrain. That's fine with me, but I didn't realize that the parking brake module was part of the drive train!

 

[Larryjb]

This is a nice video showing how to remove and reinstall the parking brake module:

If you look closely at his parking brake module at exactly 3:00 minutes, you will notice a similar crack beginning in the same place mine cracked. This is obviously a weak point. His hasn't cracked through, but mine has. At 3:56 minutes you can see the new one with no crack.

This may be something you guys want to inspect, especially if your parking brake pedal is going to the floor.

I'm not sure if this is related to the function of the auto-adjuster for the pedal height. It is entirely possible that I didn't have the equalizer adjusted right either, resulting in the inability of the auto-adjuster to remove cable slack.

There are three adjustments for the parking brake:
1) Adjust the equalizer nut to 31 pound inches. This remains a little unclear to me. I'm assuming that the torque will increase as the tension of the cable increases so that by the time you achieve 31 pound inches, you have the right amount of tension on the nut. However, if the threads of the bolt from the intermediate cable are even slightly dirty or rusted, this torque is meaningless because you will get to 31 pound inches before any slack is taken up. From the video above, GM has a new intermediate cable with no bolt, so there is no adjustment to worry about here.

2) The star adjuster which adjusts clearance of the shoes to the inner drum of the disk. This should be 0.026" or slightly less than 1/32". Most people adjust this by making sure there is no rust ridge in the drum part of the disk, then adjust the shoes so that the disk can just slide on. I achieve this by expanding the shoes until I couldn't get the disk on, then backing off the shoes until the disk would go on. Then I'd apply the parking brake and release and recheck the fit. Often I'd find I could expand the shoes another few clicks. In the end, I had the shoes adjusted so that the disk would just slide on.

Note: the instructions for my trailer brakes say that the shoes should be adjusted so that they just barely rub as you turn the wheel.

3) The last adjustment is made once the primary tension of the cable is set in Step 1, and the shoes are adjusted in Step 2. This last step is designed to take up the remaining slack on the parking brake pedal. There is a spring that is designed to apply the right amount of tension in the parking brake pedal. If steps 1 and 2 are good, you should get just the right pedal height by applying and releasing the parking brake 3 times.

At least, this seems to be what is happening in theory with the adjustments. Given that my parking brake module has a crack, I won't be able to test this out until I get the new one installed and try to adjust the equalizer as properly as I can.