How to Install Brake Chambers on Tandem Axle Trailer

Most all semi-trucks that have air braking systems, come equipped with brake chambers. The brake chambers are responsible for moving the slack adjusters back and forth. When the air is applied to the air brakes, the brake chamber rods extend toward the slack adjusters. The slack adjusters then compress the brake shoes to the brake drums. When the air is released, the brake chambers retract the slack adjusters so that the brake shoes will retract away from the drums. If the brake chambers are not working properly, then the entire braking system will not work.

Things You'll Need

• Wheel chocks
• Adjustable wrench
• T-tool
• Standard open end wrench set
• Pliers
• Hammer
• 1/2-inch drive ratchet
• 1/2-inch drive socket set
• Vise
• New brake chamber
• Measuring tape
• Chalk
• Hacksaw
• Flat file
• Teflon tape

Instructions

1. Park the trailer on a flat surface and set the air brakes. Place the wheel chocks in front of rear wheels and behind the rear wheels. Release the air to the air brakes and turn the engine off.

2. Remove any air lines from the truck to the trailer. Slide under the back of the trailer and locate the brake chambers that are mounted to the tandem axles. Begin working on the driver side rear brake chamber. Locate and remove the T-tool that is attached to the back of the brake chamber with a open end wrench. If the brake chamber does not have the T-tool attached to it, you can pick up a T-tool at most any truck parts store.

3. Pull the rubber plug out of the front of the brake chamber with your hand. Screw the threaded end of the T-tool into the threaded hole inside of the brake chamber tow to three full turns. Turn the nut that is attached to the T-tool clockwise with a open end wrench until it is locks the T-tool to the brake chamber. Keep turning the nut until the T-tool stops turning. This will lock the spring loaded plate inside of the brake chamber.

4. Locate the clevis on the end of the brake chamber rod. The brake chamber rod is attached to a slack adjuster. Pull the cotter pin out of the clevis pin with the pliers. Knock the clevis pin out of the clevis with a hammer.

5. Slowly remove the two air lines that are attached to the top of the brake chamber with a open end wrench or an adjustable wrench. Loosen and remove the two brake chamber mounting bolts from the back of the brake chamber with a ratchet and a socket. Pull the brake chamber out of the bracket and slide it out from under the trailer.

6. Place the brake chamber into the vise and tighten the vise around the chamber. Unscrew and remove the T-tool from the inside of the brake chamber with a open end wrench or an adjustable wrench. This will fully extend the brake chamber rod to its original position. Loosen the nut that is holding the clevis to the end of the rod with the adjustable wrench. Unscrew and remove the clevis from the end of the rod.

7. Measure the rod from the back of the brake chamber to the end of the rod. Make a not of this measurement because the new rod will have to be cut off at the same distance. Remove the old brake chamber from the vise and insert the new brake chamber into the vise.

8. Measure the new rod from the back of the brake chamber to the previously noted measurement. Mark the distance with a piece of chalk. Cut the rod off at the measurement with a hacksaw. Use the flat file to file away any rough edges and burs from the rod. Wrap teflon tape around the end of the threads and screw the nut and the clevis onto the end of the threads. Tighten the nut to the clevis with the wrench.

9. Screw the T-tool into the inside of the new brake chamber two to three turns. Turn the nut attached to the T-tool threads until it is flush with the brake chamber plate. Continue to turn the nut until the T-tool stops turning. This will lock the spring loaded plate inside of the new chamber. Slide the new brake chamber under the trailer.

10. Slide the threaded mounting studs of the brake chamber through the bracket. Screw the two mounting bolts onto the studs and tighten with the ratchet and socket. Attach the clevis at the end of the new brake chamber rod to the bottom of the slack adjuster with the clevis pin. Slide the cotter pin back through the clevis pin and bend the cotter pin to prevent it from falling out of the pin.

11. Screw the two air lines onto the top of the brake chamber and tighten with a open end wrench. Slowly unscrew and remove the T-tool from the inside of the brake chamber and push the rubber plug back into the front of the brake chamber.

12. Move to the other brake chamber and repeat the same process as outlined in the steps above to install the new brake chamber.

Tips & Warnings

• After the brake chambers have been installed, hook a truck to the trailer and apply the air brakes to ensure that the brake chambers are working properly.

• Most all brake chambers come equipped with the T-tool attached to the side of the chamber. If not, you can pick up a T-tool at most any truck parts store.

• Be sure to use the wheel chocks behind the trailer wheels to prevent the trailer from rolling while you are under it.

References

• Bendix Brake Chambers: Service Data
• Overdrive Online: How To Replace Air Chambers

Resources

• Truck Troubles: Air Brake Chambers Explained