2 - Rear Brake Rotor, 1979-1981 Formula or Trans Am with WS-6 pakage
1 - Left Rear Backing Plate, '79-'81 Firebird WS-6 or '79 Seville
1 - Right Rear Backing Plate, '79-'81 Firebird WS-6 or '79 Seville
1 - Left Rear Caliper, '79-'81 Firebird WS-6 or '79 Seville
1 - Right Rear Caliper, '79-'81 Firebird WS-6 or '79 Seville
1 - Left Parking Brake Actuator Arm, '79-'81 Firebird WS-6 or '79 Seville
1 - Right Parking Brake Actuator Arm, '79-'81 Firebird WS-6 or '79 Seville
1 - Left Parking Brake Cable Housing Mount, '79-'81 Firebird WS-6 or '79 Seville
1 - Right Parking Brake Cable Housing Mount, '79-'81 Firebird WS-6 or '79 Seville
2 - Parking Brake Actuator Return Spring, '79-'81 Firebird WS-6 or '79 Seville
2 - Axle Bearing Seal for your year/model Firebird's rear axle
1 - Disc Brake Pads, Set, Rear, 1979-1981 Firebird WS-6 or '79 Seville
1 - Left Rear Parking Brake Cable, '79-'81 Firebird WS-6
1 - Right Rear Parking Brake Cable, '79-'81 Firebird WS-6
1 - Left Rear Axle Brake Line, '79-'81 Firebird WS-6
1 - Right Rear Axle Brake Line, '79-'81 Firebird WS-6
4 - Rear Caliper Bolts from virtually any rear disc GM car
8 - Rear Backing Plate Bolts and Nuts from virtually any rear disc GM car
1 - Differential Cover Gasket
A/R - DOT 3/4/5 high-quality brake fluid. (I like to use Valvoline synthetic fluid or Castrol LMA GT fluid.)
A/R - Brake Cleaning Solvent
A/R - SAE 90, SAE 80W-90, or SAE 85W-140 EP hypoid gear oil. If car has a clutch-type limited-slip differential a friction modifier (limited-slip additive) is necessary as well.
2 - Axle Shafts, 1979-1981 Firebird WS-6 (do not use with a 12-bolt rear axle-equipped car!)
1. The hard lines that clip to the rear axle (the Left and Right Rear Axle Brake Lines) are usually pretty banged up on wrecked cars. Their nuts are usually stripped and/or they are rusted, often to the point of making the material porous. It is suggested that these not be acquired from a wrecked car. Reproductions are available in mild steel or stainless from companies such as Fine Lines.
2. Alternatively, you can leave in your drum brake hard lines and use medium pressure AN-3 hose to couple the drum brake hard lines to the calipers. You will need two inverted flare to AN adapters (Earl's #949543 or equivalent), two mounting tabs for the adapters (welded to the axle housing), two 13" lengths of AN-3 medium pressure hose with a -3 female hose end on one end and a 3/8" banjo on the other (Earl's #63010213 or equivalent), and four 3/8" crush washers. Using the flex hoses will reduce the binding problem that is sometimes noted with this rear disc system.
3. Many wrecked cars will have damaged parking brake cables on them. If you cannot find a suitable set of parking brake cables, you can have custom cables made for the application. Use the damaged cables for dimension reference or email me for dimensions.
4. Some model years locate the rear axle brake line junction to the differential cover bolts, some to a tab welded on the rear axle. If your car's rear axle brake line junction is mounted to the differential cover bolts and you are using the OEM rear disc hard lines (or repops of them), you will need to weld a tab to the axle housing and relocate the brake line junction.
5. If getting calipers from a wrecking yard ensure that the parking brake ratchet mechanisms in the pistons are not broken or distorted in any way. Disassemble the calipers and inspect the ratchet mechanisms in the pistons before leaving the wrecking yard. Broken or distorted parking brake ratchets render the calipers no good and replacement pistons are very expensive. Also, check the bores in the calipers for pits. Severe pitting renders the calipers useless.
6. If getting calipers from a rebuilding source, you will need to obtain the bracketry for the parking brake actuator (cable housing end bracket, actuator arm, return spring) from a wrecked car.
7. Most mechanics don't understand the presence of the rear pad damping springs and forget to re-install them when doing a brake job. If your wrecking yard calipers don't include those damping springs, replacements are available at most parts stores.
8. It is imperative that the caliper mounting bolts be straight and the surface of the pins smooth. If your wrecking yard bolts are not straight and smooth, replacements are available at most parts stores.
9. If your car has a 12-bolt rear axle, the brake pilot is of a larger diameter on the axle flange than the hole is in the rotor. This can be remedied in one of two ways. The pilot stub on the flange can be machined down so that it is cylindrical (machine off the larger brake pilot until it's the same diameter as the wheel pilot). Or, the pilot hole in the rotor can be machined up to the diameter of the axle pilot.
10. If you are not going to use axle shafts that are specifically made for the disc brakes, the brake and wheel pilot stub will not be long enough to contact the pilot hole on many wheels. This includes most OEM wheels. You should consider modifying the pilot stubs so that the wheels engage the stub. This can be done by welding additional material onto the stub and machining it round again.
1. Park car on flat, level surface. Block the front wheels. Leave the transmission in neutral gear. Remove top from brake master cylinder. Using a suitable tool, remove half of the fluid from the rear reservoir. Place fluid in a suitable container for recycling. Replace top on master cylinder, but do not flip bail to secure the top.
2. Loosen lug nuts on rear wheels. Jack car up and support using car stands. Ensure that car is securely placed on stands. Remove lug nuts and rear tires, remembering which tire was installed where. I usually mark the tread of the left rear tire with a piece of masking tape so that I know the one with masking tape goes on the left side.
3. Place a suitable drip catching container under each wheel cylinder and the differential housing. Remove the brake bleed screws. Remove the differential cover. Allow fluid drainage into the containers. When drainage is complete, place drained fluids in suitable containers for recycling.
4. Remove clevis retaining clip from pivot pin on brake pedal. Remove brake booster clevis from pivot pin/brake pedal. Disconnect hydraulic fittings leading to the chassis from the combination valve. Disconnect brake fault wire from combination valve. Remove four nuts retaining booster to firewall. Remove brake booster, master, and combination valve.
5. Remove rear parking brake cable housing guides from frame rails. Disconnect the rear parking brake cables from the intermediate parking brake cable by loosening the parking brake adjustment and sliding the cables out of the cleat. Unscrew the parking brake cable housing strain reliefs from the frame rails and remove. Unseat the parking brake cable housings from their chassis mounts.
6. Remove differential fill plug and place in a clean, safe spot. Rotate the rear differential until you can access the pinion shaft lock screw. Remove the pinion shaft lock screw. Slide the pinion shaft out of the differential carrier and place in a clean, safe spot.
7. Remove axle shaft seal and discard. Loosen hydraulic fitting at brake hard line and wheel cylinder. Remove four backing plate retaining bolts. Slide drum brake assembly off of axle housing, un-thread parking brake cable from chassis, and discard. Repeat for other side.
8. The passenger side parking brake cable needs to be suspended from the sheetmetal frame rail. There are a couple of location holes for the bracket (one for the locator pin on the bracket, one for the screw). Drill up the upper hole so that a 5/16-18 Riv-Nut (or similar threaded fastener) can be installed and install the threaded fastener.
9. Clean the axle seal seat area in the axle tube. Install new axle seals. Install passenger side brake caliper bracket. Use new crimp-lock nuts and grade 8 fine pitch bolts. Torque to 35 lb./ft. (oiled). Lubricate the lip of the axle seal. Insert axle into axle tube and differential carrier, being careful not to drag the unmachined surfaces or splines of the shafts on the seals or bearings. Repeat for other side. Install C-clips into their grooves at the ends of the axles and slide axles back out as far as the C-clips will allow. Install differential pinion shaft and its locking bolt. Torque locking bolt to 20 lb./ft. Clean the differential cover and its mating face on the axle housing. Install the differential cover with the new differential cover gasket. Torque differential cover bolts to 23 lb./ft. Fill differential housing with the proper lubricant and limited-slip additive if necessary. Insert differential housing fill plug into differential housing and tighten.
10. Insert the driver side parking brake cable into the frame and seat the cable housing into its frame mount. Install cable housing strain relief and torque screws to 16 lb./ft. Repeat for other side. Screw retaining bolt for passenger side cable bracket into the frame rail.
11. Wash hands. Wash rotors with solvent to ensure that the surface is not contaminated. Install rotors on rear axles. Ensure that pistons are fully compressed into brake calipers. If pistons are not fully compressed, use a compression tool (do NOT use a C-clamp) against the old inboard brake pad. The old brake pad prevents the piston from rotating as the piston is compressed into its bore. Ensure that the "D" shaped dimple in the piston is aligned with the nipple on the old inboard pad and install the pad. Place the compression tool against the pad and compress the piston. When piston is fully compressed, remove compresison tool. Discard old brake pads. Install new brake pads into caliper, ensuring that the nipple on the inboard pad fits into the "D" shaped dimple in the face of the piston. Ensure that damping springs are properly installed onto the pistons and the inboard pads. Clench the retaining ears on the outboard pads onto the calipers. Install calipers on their brackets. Insert retaining bolts and torque to 35 lb./ft.
12. If you are installing new brake hoses, install the brake hoses onto the brake lines at the axle first, then onto the caliper. If you are installing new hard lines, remove the drum brake hard lines from their retaining clips on the axle and install the new ones, starting the installation at the Tee junction with the flexible hose.
13. Using parking brake actuator arm for the passenger side caliper, rotate the parking brake screw in the apply direction until both pads contact the rotor. Install parking brake actuator arm onto screw, placed against its stop. Insert parking brake return spring between parking brake actuator arm and caliper cable housing mount. Thread cable and housing through caliper cable housing mount and ensure that all latches on the cable housing are seated properly on the cable housing mount. Thread cable through spring and into the parking brake actuator arm. Repeat for other side. Hook rear cables together and join to the front cable and adjust so that there is very slight tension in the cables when parking brake is not applied. Apply and disengage the parking brake several times. Readjust tension on cable as necessary.
14. Install 4-wheel disc power brake booster onto firewall. Install four retaining nuts onto studs on firewall and tighten. Install brake booster clevis onto pivot pin/brake pedal. Install clevis retaining clip onto pivot pin/brake pedal. Install booster pushrod into the front of the booster. Install master cylinder on booster. Install proportioning valve and bracket onto booster/master combination. Install two retaining nuts and tighten. Install hydraulic lines between master cylinder and proportioning valve. Install brake fault wire on sensor in proportioning valve. Connect hydraulic lines to outputs of proportioning valve.
15. Fill brake reservoirs part way. Using a rubber mallet, lightly and rapidly rap on the front of the master cylinder to expel bubbles until the number and size of bubbles becomes very small. This will take quite some time, but is more effective thanb "bench bleeding."
16. Fill reservoirs and install cover on master cylinder. Bleed rear brakes, passenger side first using light but firm strokes of the brake pedal. This will require removing the reservoir cap and refilling the master cylinder reservoir several times before both sides are properly bled. Bleed front brakes, passenger side first using light but firm strokes of the brake pedal. This will require removing the reservoir cap and refilling the master cylinder reservoir several times before both sides are properly bled. After all four brake positions are bled, re-check each brake position to ensure that there are no more air bubbles in any of the calipers, starting with the passenger side rear brake. Re-fill master cylinder reservoirs.
17. Reinstall tires onto car. Install lug nuts finger-tight. Lift car with floor jack and remove car stands. Lower car until part of its weight is supported by the jack and part by the tires. Torque lug nuts to 75 lb./ft. Lower car to rest on ground. Once again, apply and disengage the parking brake several times to adjust the rear brakes. Drive carefully to get the feel of the new brakes. Enjoy!
Control Cables
13230 E. Firestone Rd., Unit K
Santa Fe Springs, CA 90670-7075
562-802-1122
Fine Lines
650 W. Smith Rd.
Medina, OH 44256
216-722-7641
Special thanks to James M. Rowe for suggestions on improving this article.
Copyright 2000 Steven Chin. None of the material presented on this site may be reproduced without the express consent of its' copyright holder.