One of the main goals for my car when I started was to build a reliable performer that was upgraded in almost every regard from what you would have gotten from the factory.
Braking is often one of those overlooked aspects that many seem to ignore, but it is essential for an all around performer. My mustang came with power brakes and discs upfront and for some this would have been sufficient.
For me choosing to stick with drums in the rear was however, not acceptable so I began looking into rear disc conversions. Like many of you out there I am on a budget and after seeing how much rear disc kits can cost; upwards of $600 in many cases, I decided that it may not be worth the cash outlay.
That's when I stumbled across a small write up on using the rear disc set up from the Ford 8.8 and more specifically the one found in the numerous Crown Victoria and Grand Marquis. Utilizing crown vic parts and using some adapting hardware (available on ebay, link will be supplied) one is able to put rear discs on an 8" or small bearing 9" axle for less than $350 in most cases!
The first thing you must do is determine which axle you have. Any 8" will do but if you have a 9" like me then you need to make sure that it is a small bearing 2.835" diameter with a flange bolt pattern of 3.3125" x 2.0". If you have the big bearing 9" then you should pursue an Explorer based set up.
The next step is obtaining the necessary parts and from this will determine what spacers you will need. There are two sets of years that are applicable for this swap. The first set are cars from 1991 to 1995 and the second are cars from 1996 to 2002. The 96-02 set up is preferable as the caliper backing plates come with large dust shields, but the hardware for this kit is usually somewhat more expensive.
Be sure to obtain all the parts from the set up: caliper backing plates, backing plate retaining bolts and nuts, calipers, flex lines, rotors, e-brake hardware & cables, axle wheel studs. Not all the parts need to come from the salvage yard, the e-brake shoes and hardware can be purchased new from your local parts store for example. The parts from the two year sets are not interchangeable so stick with one set when collecting your parts.
Pictured here is the 91-95 backing plate from a 92 crown vic, I chose this set of years because my local salvage yards had many more of these cars readily available.
After you obtain the necessary parts you will now need to either purchase or fabricate the necessary spacers that allow the set up to adapt to early mustang rear axles. For ease of install I opted to purchase these spacers online, and included with them are detailed instructions on the modification of the axle and install so I would highly recommend this.
Included are a set of bearing spacers that compensate for the difference in the caliper backing plates and the old drum backing plates, and hub spacers that allow for the centering of the rotor on your current axle hubs. For the 91-95 years included are some washers that need to be installed on the backing plates prior to install on the axle, they allow for proper tightening of the axle retaining flanges. The entire kit is $50 which may seem steep for some small pieces of metal, however the entire job is laid out nicely in the provided instructions.
1965-1973 Mustang+ Rear disc brake adapting parts 9" 8":eBay Motors (item 320388531426 end time Jul-23-09 23:29:53 PDT)
After obtaining the spacers you will need to have the bearing spacers installed on your axle along with the crown vic wheel studs. The studs ARE necessary as their longer length is required and they have a small shoulder which is needed for the rotor's proper install. When doing this you should replace the bearings on your axle as well as the locking sleeve. The order for install is essential and should follow this:
Next you will need to modify your axle flanges to accept the new backing plates. From the factory they are D-shaped and will need to cut into a more rectangular shape.
Finally after all the prep work you may now go ahead and start the actual installation of the new set up. Installing the e-brake hardware on the backing plates is much easier with them off the axles and the bearing should fit through the center fairly easily.
Here is a diagram of the e-brake assembly that should help in adjusting them to proper spec.
IMPORTANT! When installing the backing plates and axles into the housing you must make sure the bearing spacer is seated properly against the bearing before tightening down the retaining flange! I used a light coating of grease to get the spacer to stick to the bearing and a coat hanger to maneuver it into position. This is very important and when done correctly all the retaining bolts should tighten evenly. This is probably the most hassle ridden part of the install and may take a few attempts.
Since both sides are the same I opted to mount the backing plates upside down so the parking brake cables would mount a little easier, but you may choose otherwise. After this the assembly should look like this:
Now you can add some threadlocker to the hubs and install the hub spacers. The ones in the kit are not meant to fit flush against the hub flange and are meant only to center the rotors.
Now you can install the calipers
Finally the vehicle specific adapting will have to take place, mounting the flex lines, bending new brake lines, mounting the e-brake cables, bleeding the brakes, installing a proportioning valve if needed etc. These are all formalities that are specific to the car that you have and will require a little bit of thinking on your part, but the lion's share of the work is now done and you should be well on your way to four wheel discs!
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