Replacing the Rear Brakes on a 1989 Chevy Dually
Working on a Dually
The truck we will be working on is a 1989 Chevrolet Silverado "Dually," that is, a truck with four rear wheels instead of two.
This year, 2019, this model turns 30 years old and celebrates its inauguration into the "Classic Truck" hall of fame. This is exciting! The value of these trucks will increase! In recent years the value for this truck has been plummeting. Now, it will only gain value as a classic truck.
With this in mind it's time for those of us that own one of these trucks to start restoring them properly. I have used and abused my truck. It could use some TLC. It is the heavy duty 1-ton 3500 model with dual wheel set-up on the rear tires. I expect it to work for me and work hard.
This dual wheel set-up has been known to deter some home mechanics—like me!— from working on these models. There is not any special tool or procedure to remove duallys. The task is quite simple, but heavy. The tire and rim used on heavy duty trucks such as this weigh far more than the average tire, and now you have two of them on each side. Daunting, yes. Insurmountable, no.
Inside the Rear Brake Drums After 15 Years!
When the brake light illuminated, some 15 years ago, I looked at those dual tires and thought, "It can wait. It's just the master brake cylinder out of balance." And I was right, I ran it for another 15 years with the light illuminated, until, recently, that little red light began to flash. When the brake light starts flashing (5 times in intervals) it means the truck is having a total brake system failure. In other words, Stop driving it now! That truck hauls some seriously heavy trailers. I stopped driving it immediately and resolved myself to the fact I was going to have to do a brake job on it.
I didn't want to dive into this brake job, but I had to, and ya know what? It wasn't all that bad, but it was heavy! So, come along with me and be the first to see the inside of the rear brake drums of this truck for the first time in 15 years!
Replacing the brakes on a dually 3500 can be done by the backyard mechanic, but you need to be cautious and pay attention. That's why this article includes cautions about several steps in this procedure. I've seen fingers lost, and toes and fingers smashed. Heavy duty trucks require heavy duty equipment including heavy brakes, heavier than you may be used to. The drum alone on this truck weighs more than 40 pounds.
Tools You'll Need
It's faster and easier to complete a job if you have the tools you're going to need set out and ready. For this rear brake job you will need:
- New brake shoes
- Brake grease
- Sockets and socket wrench
- Breaker bar or pipe for leverage
- Brake cleaner (or soap and water)
- Flat-head screwdriver
- Jack stands
- Tire wedge
1. Remove the Wheels
Locate your truck in a clean, level, spot. If you have a dirt yard lay a tarp down and drive onto it. The brake process for the 1989 Chevrolet Silverado Dually involves removing the drive axle, and it is very important that foreign objects like dust and dirt not come into contact with the removed axle or penetrate the axle housing while you work.
- Set tire wedges on the front wheels to deter the truck from rolling when the rear end is lifted off of the ground.
- Do NOT set the parking brake! This would lock up the rear wheels and give you trouble trying to remove the drum.
- DO put the truck in the Park position.
- Locate the proper socket (21 mm sounds about right) and use your breaker bar to break the lug nuts loose. The depth of the wheel on a dually does not allow access to the lug nuts with a standard socket wrench. I used an 18" extension attached to a breaker bar. To steady the 18" extension while I stood on the breaker bar I put a jack under the connection (see photo).
- You can either jack up the entire rear end, since you will be working on both sides, or you can jack up one side at a time. Set on jack stands. Do NOT use the jack as a stand! If the jack lowers itself for any reason, you will get hurt.
- Decide which side you will replace first, remove the lug nuts the rest of the way, and set them in a safe place where they won't be lost.
2. The Dually Wheels
Once you have the lug nuts off, the outside tire will begin to fall off the screws. Prepare to remove the outside tire and set it aside, while paying attention to the inside tire, because the inside tire may follow the outside tire as you remove it. Be careful your fingers aren't smashed between the two tires as you remove the outside one. If necessary you can screw a lug nut or two onto the posts to keep the inside tire from falling off while you set the outside tire to the side.
Now remove the inside tire. It has nothing keeping it in position (unless you used a lug nut to hold it), so it should just slide right off after the outside tire. If it doesn't, you can take a hammer to it and tap around the mounting area, being careful not to tap the lug nut bolts.
3. Remove the Axle
Once you have the tires removed the axle needs to be removed in order to get the brake drum off.
With the appropriate socket size and wrench remove the eight bolts holding the axle in place. You may need to use the breaker bar for this. Penetrating oil will help loosen rusty old bolts. Place the bolts somewhere you won't lose them or get dirt on them.
The axle will slide right out now. Again, if the axle plate is stuck, tapping with a hammer will break lose the metal. Grasp the edges of the axle plate and pull. You may have to twist a little bit to make the gears release the axle end. Then slide it all the way out and set it aside in a clean, safe spot.
The Axle Slides Right OutClick thumbnail to view full-size
4. Remove Retaining Clip & Key
With the axle set aside in a safe, clean, spot, it's time to remove the retaining clip and key. When these have been removed the thrust washer needs to be unscrewed. Once the washer was unscrewed the brake drum will come off.
- Using needle nose pliers remove the retaining clip.
- With either a magnet, needle nose pliers, or tweezers, remove the "locking key."
- Using the tip of the needle-nose pliers or Phillips-head screwdriver, turn the thrust washer in a counter-clockwise direction. The thrust washer should turn easily. Keep turning until it comes off.
These three pieces you just removed are very important and can prove to be pricey to replace. Set them aside in a safe, clean, spot as well.
Removing the Clip, Key and Thrust WasherClick thumbnail to view full-size
5. Remove Brake Drum
The brake drum is ready to come off now. IT IS HEAVY! Wear sturdy shoes and be aware of where your fingers are when you are removing it. It is an awkward position leaning into the wheel well, and the brake drum can be surprisingly heavy, so use caution.
If the brake drum doesn't slide right off, there is an access hole on the back side of the brake that allows adjusting. Using a standard head screwdriver, lift the retaining lever so you can turn the brake actuator with another screwdriver. This will relieve the pressure the brake shoes are putting on the brake drum. If the drum still won't come off, use a hammer to tap around the circumference of the brake drum until it comes free. Once it comes free it can easily fall right off, so pay attention!
Set the brake drum aside if it is easy enough for you to move it. If you can't easily move it, leave it where it is and it won't be much of a nuisance for you to complete the brake job.
Rear Drum Brake After 15 Years
The Wheel Cylinder
The wheel cylinder was leaking on this truck. I replaced it. Here is an article I wrote about wheel cylinder replacement.
6. Rebuild the Brakes
The inside of this drum brake wasn't all that bad for 15 years plus! There was a good amount of brake pad left, so it looks like it wasn't even working and something was definitely leaking. I suspect the wheel cylinder was leaking.
There are multiple methods to go about disassembling the brake system here. I usually start at the bottom. This tends to keep the whole thing together until I want it in pieces. I have started from the top but the entire thing fell out and pieces were everywhere. So, I stick with the bottom method.
- Remove the blue spring at the bottom with a screwdriver or other device. This will allow the adjusting lever to come out.
- Remove the left side hold down pin. I use a socket wrench with a long socket on it to press down the spring and remove the pin from the back. The left shoe will be loose now and the strut will come out.
- The left shoe can now be swung upwards to remove the top orange spring and the shoe is now off.
- Remove the hold-down pin on the right side. This will release the shoe will be so it will be able to swing upwards to relieve the blue spring and the shoe return spring it is attached to.
Leave the parking brake lever attached unless you are replacing it.
Use Brake Cleaner to clean the area. DO NOT blow it out with compressed air or by mouth. This dust contains asbestos which is dangerous to humans! Only use brake cleaner or warm soapy water to clean the brakes!
7. Install Brake Parts and Close Up
The drum brake is downright pretty with all its new parts! I decided to buy a new actuator. Since I haven't been in here in 15 years and don't plan on being back in here for another 10 years I decided to replace it. It came with a new lever and spring. The old one was frozen. I soaked it in gas for a couple of hours just to get it to screw back and forth.
Putting the brake back together can be irritating. You might feel like you need four hands instead of two, but it can be done. After you grease the back plate at the wear points (usually visible as shiny spots on the back plate) put the springs on the brake shoe and tilt the brake shoe up so you can attach the springs at the top. Then, lower the shoe into position, set the strut bar with spring into position, and get that hold-down pin in there. After you get the hold-down pin in it will be easier to assemble. I used my knee to hold the brake shoe in position while I pressed the pin in.
Make sure the wheel cylinder pins are in the proper position on the brake shoes.
The brake adjuster can be set into position at the bottom and the blue spring stretched behind it.
Carefully lift the brake drum up into position paying close attention to the axle entering the drum brake hole correctly. There are bearings in there that you don't want to damage!
Once the brake drum is in position put the thrust washer back in, screw it down firmly, insert the key and retaining ring.
Slide the axle back in. Gently turn the axle until it drops into position, keeping it as level as possible while sliding it in so it will go into its correct position.
Put the bolts back into the axle plate and snug down to 115 inch pounds (check your exact vehicle for the inch-pound value).
Put your tires back on, with the hubcap if they had one.
8. Important Last Step: Adjusting the Brakes
This next step is skipped by MANY home and business mechanics! The rear brakes need to be adjusted. If you don't adjust them the brake pedal may very well travel to the floor or near to the floor!
Lay on the ground and look at the back side (or inside) of the brake under the truck. There is a small access hole along the bottom. If the access hole is not open, use a screwdriver and small hammer to open it. Using the screw driver twist the adjuster screw until it becomes firm to twist. Get out from under the truck, check that the front tires are still blocked firmly and put the truck into neutral so the rear wheels will spin by hand. Now go back to the rear wheels and turn it by hand. Are the brakes dragging on the wheel? If not, put the truck back into park and get under that wheel and adjust the adjuster with your screwdriver again. Turn the wheel by hand again. Are the brakes dragging slightly yet? If not, do it again until you can hear the brakes barely dragging on the brake drum. If yes, you can hear the brakes dragging on the brake drum, then you're done!
Lower the truck, check the torque on the lug nuts again, and take it for a spin with your new brakes!
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.