Though the design in this...
Though the design in this last exploded view is slightly different, it shows what you will see after removing the rotor. The rotor's integral parking brake drum hides the shoe. GM sells all of these pieces as a kit for $164.23 per side.
After disassembling your current...
After disassembling your current drum brake setup, the previously pictured parts will simply bolt onto any '65-and-newer 8.2-inch, 8.5-inch 10-bolt, as well as 12-bolt rearends. This setup will also work on a '64 rearend, but some of the steps are different (see sidebar). A mockup of the installation shows how it is done. Start by removing the axles and replacing the current wheel studs with new ones at least an inch longer. Next, slide the bearing retainer, backing plate, and dust shield onto the axle as shown here for the driver side (left), and slide the axle into the rearend. Use stainless steel grade-8 bolts with lock washers, and bolt the axle to the axle flange. Shim as necessary to center the caliper, and torque the axle flange bolts to 35 ft-lb.
After you have slid the rotor...
After you have slid the rotor onto the wheel studs, mount the brake pads into their retaining cage and place them over the rotor. Bolt the retainer bracket to the backing plate using lock washers.
Slide the new caliper over...
Slide the new caliper over the pads and bolt it to the retainer plate. At this point, you are ready to install new brake lines, an adjustable proportioning valve, and if needed, a new master cylinder.
The dust shields, calipers,...
The dust shields, calipers, rotors, and pads can be purchased from your local dealer or parts supplier, and we strongly recommend that these particular parts be new items only.
The caliper we purchased at...
The caliper we purchased at our local dealer was a remanufactured unit that set us back $36. It is a single-piston, full-floating unit that will be a huge improvement over the factory-installed drums.
Chaudary used a brake line...
Chaudary used a brake line bracket from the front of a Chevy 3/4-ton truck for his conversion. He slid the line through the hole in the bracket and used a retainer clip at the coupler to hold it to the bracket, just like the fac-tory does for front brake lines. Next he drilled holes and bolted the bracket to the shock mounts on the rearend. He then hooked up the lines and bled the brakes. Then he clipped the original GTO front parking brake cable to an S-10 rear parking brake cable and checked for proper operation.
This will allow you to remove the four nuts on the end of the flange and take off the backing plates and disc brake dust shields. The backing plates are the most important pieces in the conversion, because even though everything else can be purchased fairly inexpensively from your local GM dealer or parts retailer, the plates are quite expensive new, listing at $74.06 each. And it's one of those situations where used versions for $50 or less per pair at your favorite salvage yard will work just as well. These backing plates also have an integrated parking brake in them.
"Our dust shields were almost toast," Pooni says, "so we opted to get new ones from our local GM dealer parts department ($19.70 U.S.). Keep the old dust shields you get from the yard to match them up with the new ones from GM." Why? They made two different versions-on the S-15 the calipers will be at the 2:00 position and on the Jimmy and Envoy they will be at the 11:00 position. They work equally well, so there really isn't a more desirable location, though aesthetically one may appear better than the other, depending on the owner's preference.
The rotors are a really nice design, measuring 11.625 inches in overall diameter. They also feature an integral parking brake drum that lends itself well to adaptation to earlier cars. The calipers are a fairly conventional full-floating, single-piston design that may not be as exotic as some aftermarket units, but are very effective and light-years ahead of the drums you're replacing.
Master Cylinders, Proportioning Valves And LinesAs the scope of this article is limited to getting the brakes on the rearend of your choice, you are left to sort out the many options in the areas of master cylinders, proportioning valves and brake lines. Every case is likely to have unique requirements that are beyond the scope of a sin-gle magazine article. Depending on the year of your particular Pontiac and the configuration of the front brakes, you may be able to work with what you have or you may have to upgrade. Either way, it is imperative that the front and rear brakes work efficiently and in harmony with one another, and it's your job to make sure that happens.
For safety's sake, make sure your brake lines are in good condition. Replace whatever is needed to ensure they are all up to snuff. A modern master cylinder should be used. If your car came from the factory with a disc/drum setup, you'll be able to reuse the stock unit, provided that the egg-shaped pressure-booster in the rear lines is removed. Its job is to increase the line pressure to the drums, as they require more pressure to use than the discs. It is not required with rear discs.
From there, installing an adjustable proportioning valve will help you tune the proper front-to-rear balance. You won't need to remove the proportioning valve at the master cylinder, though an adjustable proportioning valve will need to be downstream of the distribution block. A Wilwood unit will cost between $40-$80, depending on whether you want a lever (PN 260-8420) or more economical knob style (260-8419). Pooni's is mounted on the frame, near the front of the side rail.
If you have a four-wheel drum system and are upgrading to discs up front as well and would like to go the aftermarket route, Stainless Steel Brakes, Wilwood, Baer Racing, and countless others market affordable, high-quality master cylinders that will work in your particular application and generally run around $200.
In Chaudary's case, he used a '76 Corvette master cylinder because Vettes came with four-wheel discs that year, and it looked stock at a casual glance. The system has proven to be completely effective and reliable.
Follow along with the photos and captions to learn more about this clever mixing of old and new.
Special thanks to Jason Walton at Randall Farnsworth Group for providing the GM part numbers and prices.
Conclusion
Once everything is bolted to the rearend, there are still a few things to do. To finish up, cut the existing brake line, install a threaded coupler, and flare the line. Attach flexible brake line to the coupler. Here you may want to fabricate a bracket to hold the flex line to the rear end. Next you can set up the parking brake.