Disc brakes have many advantages over drum brakes. These are inclusive of better heat dissipation and braking efficiency, as well as a simpler design with fewer moving parts. Most new vehicles and light trucks come from the factory with four-wheel disc brakes, but this wasn’t always the situation. Several manufacturers supply rear disc brake conversion kits. Here’s a step-by-step guide to disc brake conversion.
Park the car on a flat and level surface such as a garage floor. Use the lug wrench to loosen the rear lug nuts one turn each. Raise the car enough to work on comfortably. Put the jack stands either under the axle housings or the rear frame rails and carefully lower the car onto the stands. Finish removing the wheels.
Draw the brake drums off the axle flanges. You may have to hammer around the edge a number of times to loosen the drum greatly to remove it.
Place the catch pan under one side. Use a flare nut wrench (3/8″ or 7/16″) to loosen and remove the brake line on the wheel cylinder. Also known as a line wrench, flare nut wrenches are great when you have to be careful about not damaging a brass or aluminum nut. Cap the line with a vacuum plug or cap to keep the fluid from draining out of the master cylinder.
Disassemble the rear brakes. Take out all the hardware. Remove the parking-brake cable from the actuating lever and pull it through the backing plate after squeezing the retention clips.
Remove the axles from the rear end. Most GM axles are secured in the rear end with clips. The differential has to be drained and the rear cover taken out in order to remove these C-clips. On Ford eight and nine inch rear ends and Mopar rear ends, the axles are secured in the axle housings by bolts that are accessed through holes in the axle flange. Be careful to not spoil the seal when removing the axle. Remove the backing plate.
GM owners will now be required to remove the four bolts securing the backing plate to the axle housing and then remove the backing plate. Clean the mounting flange on the axle tube with brake cleaner.
Mount the caliper brackets. The exact procedure for this will differ depending on what make and model vehicle being worked on and the particular kit. For example, some kits may have upper and lower caliper brackets, while others might have front and rear brackets. Ensure the bracket bolts are properly torqued.
Now mount againl the axle. Reinstall too the C-clips on GM axles and line up the bearing retainers on Ford and Mopar products and bolt them into place. Slide the rotor into position.
Some kits will need that you change the lug studs due to rotor thickness.
Mount the calipers with the supplied nuts, bolts, and washers and torque them as specified. Make sure the calipers are mounted with the bleeder screws facing up.
Attach the parking-brake cable to the actuator rod/arm and install any cables or adapters supplied with the kit, and adjust as required
Link the brake lines to the calipers. In most instances, this will actually require the use of rubber hoses that may or may not come with the kit
Crack the bleeder screws open to allow the calipers to fill with fluid while topping off the master cylinder. Once fluid starts coming out, close the bleeders and bleed the brakes, paying close attention to the rears.
If at any time the master cylinder runs dry or close to dry, it will need to be bench-bled before bleeding the rest of the brakes.
Test the parking brake to be sure that it works properly by setting it and trying to rotate the wheels by hand. Start the engine and shift into reverse while idling. Apply the brakes and ensure the wheels stop spinning. Shift into drive and carry out the same test. Release the brake and increase the speed slightly and step on the brake. If everything works properly, lower the vehicle and give it a test drive.
Don’t push the car fast until you’ve tested the brakes at lower speeds. Just like with any disc brake job, hit the brakes a few times from a speed of about 30 mph to be sure the pads are bedded properly.
You can equally perform a disc brake conversion from drum brakes on front-wheel-drive vehicles. The major difference is in how the drums will be taken out. There is also an axle hub that has to be removed instead of an axle.