Installation of Crown Vic Rear Discs on a Classic Mustang by Keven Coats

Comments in Red By Dennis Harrelson

This is the write up for the late model Crown Victoria or Mercury Marquis rear disk brake setup swap into the early Mustangs. It fits the small bearing 9" rear end, or 8" rear end in the early Mustangs.

This details a heck of a lot of steps, and it's really not as complicated as it sounds, but is difficult to describe in text. I'll have to take some photos when I have a website available.

Pros for this swap include;

• 1. Cheap! (<$300).
• 2. Solid and light, much lighter than any other disk setup I've seen.
• 4. Incredible difference in braking feel and confidence.
• 5. Good looking (as compared to drums!) through the wheels.

Cons include:

• 1. Solid rotor (11.4").
• 2. Phenolic pistons (unless you can find police or station wagon calipers).
• 3. Difficult to install and use e-brakes.

Every Crown Vic and Merc Marquis from '92-'95 used rear disk brakes. Later models use a similar, but slightly different setup. This swap message only covers '92-'95 brakes, as this was something I had more information on than the later years of Crown Vics.

The resulting setup from this swap is some nice shiny disks on the rear of your early Mustang (or other car with suitable rear end) measuring 11.4" in diameter, non-vented, with parking brakes located inside the drum part of the rotors, just like the Explorer setup, only fitting the small bearing 9" and regular 8" instead of the big bearing 9".

This write up details a '68 Mustang swap, but others should be similar. Police use this brake setup, with one change (steel piston calipers), routinely for fast stops from over 100 mph. Explorers use the same setup as well for towing, so it's got to be decent. I've never noticed any brake fade from it, although my car doesn't see too much high speed track time.

With this swap I feel very confident in very hard stops, contrary to my previous drum setup that occasionally wanted to switch lanes by itself at the worst times. Now I can stab the brakes and all the tires bite pretty hard. It's a much more controlled stop. In fact, I'd venture to say that it's one of the best braking setups I've felt. Much better than any production car I've ever driven.

What you need:

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• About 14 hours of time, including a few parts store runs (a friend is handy too!)
• Calipers (about $35 each with $50 core)
• Old caliper hose ends to see the new flare and get the flare nuts(to match, since you'll have to flare your existing brake lines)
• Rotors ($25-$50 each)
• Brake pads ($25 set)
• Caliper hoses ($20 each)
• Rear axle mounting brackets from a salvage yard (price varies, got mine with cables and calipers for $55 pair!)
• Emergency brake cables from salvage yard(up to the middle of the car) All from a '92-'95 Crown Vic or Merc Marquis

• wheel studs that are 1 3/4"-2" long, 1/2"x 20 threads with stock knurl of .625" (these are difficult to find sometimes, stock length is 1 5/8"). (The lugs from the donor C.V. will work)
• 1/8" steel cable end that you can bolt on a steel cable (hardware store)
• Some scrap steel
• An old wheel bearing is handy, and don't forget brake fluid

• axle bearing spacers
• brake hose mounting tabs
• e-brake mounting
• e-brake cables

• Something to cut 1/4" steel like sawzall, etc.
• pneumatic cut off tool (with 3" wheel)
• Welder or torch with brazing rod (not necessary if you clamp the end hose brackets on)

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• Hard lines - Ridged brake lines that aren't supposed to flex
• Brake hoses - Rubber hoses that fit between calipers and hard lines.
• Disk brake mounting brackets- Brackets made of aluminum off of the Crown Victoria that go between the axle flanges and the disk brake calipers. (My donor was a '93 Marquis, the brackets are steel.)
• axle retaining plates- Plates used to hold the axle bearing to the disk brake mounting brackets, or originally to the drum brake mounting brackets.
• Axle retaining plate- plate that holds the axle on the car by holding the pressed on rear axle bearing solidly inside the place where they are supposed to go (bearing ends on each side of the axle).
• Hose brackets- Things to mount the ends of the rubber hoses to so they fit to the hard lines.
• e-brake- Emergency brake.

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Go to your local salvage yard and get the calipers, mounting brackets, and e-brake cables, don't worry about rotors unless you get a really good deal. You'll probably pay more to buy and turn a set of used rotors than you would to buy them new. You'll want to watch them take off the mounting brackets so you can see how the e-brakes go, and how the mounting brackets mount on the axle. Get every little part you can, you never know what you'll need in these type swaps. Pay attention to the orientation of the brakes on the Crown Vic. The caliper mounts on the rear of the disk on the driver's side, but opposite (on the front of the disk) on the passenger side. This is so that Ford can use one casting for both brackets.

I personally wouldn't use used calipers when replacing them is so cheap. I only want to do this once. But, you still need to get the used calipers as the core prices are very high (about $40-$50!), so you'll need them to get this money back when you buy the new or rebuilt ones.

If possible, get the steel piston calipers when you buy new. The regular pistons in these calipers is phenolic. They don't stand up to heat quite as well as the steel ones that the police and station wagons use. Not sure if Explorer calipers use them or not, or if they interchange. (added note: I've used phenolic pistons now for many years and so far, they work fine.)

If you want to clean and paint the outside of the hub of the rotors, or calipers, now is the time. Use 1200 degree temp paint or higher.

Replacing the brakes:

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• 1. Disconnect the negative terminal of the battery (ha ha! Not really, I just like saying that because it's so completely irrelevant and if I were a Chiltons book, that's what I'd say. I'll get serious again... Ahem.)

• 2. Jack up the car, preferably by the rear axle spring perch plate, and take off the rear wheels and drums. If you don't know how to do this, you shouldn't attempt to do this swap!

• 3. Take off the drum backing plates and unscrew the brake line connection. Then hurl the junky drums and backing plates as far as you can towards the trash (O.K. really, I said I'd be serious...).(Actually these are worth something. I think I got about $25 or so on eBay)

• 4. Slide out the axles temporarily, making sure to be careful with the axle seals (if you're not replacing them) and stuff a clean rag in the housing end to seal the inside of the housing from the hacking you'll do on the axle ends.

• 5. Cut off the lower part of the housing end so that it fits into the new disk brake mounting brackets. The Crown Vic rear end has rectangular ends, 8" and 9" housings have a circular end with the top side cut off. Cut the bottom part off flat to match the top. This is heavy steel, so a sawzall or other suitable cutter will be necessary. A right angle grinder will work, but you'll be there for a _long_ time.(Use a thin cutting wheel. works very well)

• 6. Test fit the disk brake mounting bracket on the axle. The bolt holes line up!!!

• 7. Bolt on this mounting bracket temporarily and turn your attention to working on the axles (that are already out of the car, right?!).
• 8. Pound or press the old studs out of the axles. They are probably too short, since the rotors are about 1/8"-3/16" thicker than the drums.

• 9. Press in the new studs with a press or a lot of washers piled up with a nut to draw it through with an impact wrench (use oil on the threads and everywhere). This is a pain staking task!

• 10. Now is the time to replace your wheel bearings and/or seals!

• 11. Slide in your axle temporarily and see how your axle retaining plate (on your original Mustang axle, used to hold the axle onto the flange) doesn't fit inside the new disk brake mounting bracket indention. Cut off the lower part of the plate to make it rectangular too (just like the axle flange) to fit.

• 12. Now we have a problem. Once you slide in the axle you might notice that the wheel bearing is held between the rear end axle housing inset and the retaining plate, but the retaining plate is not up against the bearing on the outside, since the disk mounting bracket is thicker than the drum backing plate. On my car, and probably most others, the new disk brake mounting bracket is .130" thicker. That means we have to have some spacer to put between the axle bearing and retaining plate or the wheels will slide in and out .130" every time we take a corner.

  Let me rephrase to make sure we're clear. The stock Mustang drums are held on the axle by a piece of sheet metal that forms the back of the drum brakes. The Crown Vic disks are held on to the axle by the disk mounting bracket, and it's made of cast aluminum. The cast aluminum is thicker than the sheet metal used for the drum brakes, so we'll have to make up that .130" thickness difference by putting a spacer in there to keep the bearing solidly wedged in between the axle retaining plate and the bearing end (where the bearing is supposed to fit inside the axle).

  I made one the hard way by slicing the outer race of an old axle bearing into .130" segments (one for each axle). This makes the spacer the correct size and shape. Dimensions aren't that critical, but you don't want the bearing to slide sideways, so some spacer must be made, and it's best if the hole in the spacer doesn't interfere with the seal on the axle bearing, so it must be thin, but relatively strong.
  To slice an old bearing, I mounted the axle it was on (from another car) into my vise and used the pneumatic cut off tool to cut around the bearing as it slowly rotated. This way the thickness was relatively constant. I used calipers to double check after finish grinding it on my wheel grinder. This takes a while (about 30 minutes of continuous cutting), because you are cutting a 3/16" thick slice of incredibly hard, high grade steel (the bearing). The second slice takes less time since the bearing isn't as thick in the middle of the race as it was near the end.
  I slowed the bearing as I cut it with an old shop rag. Beware, this usually results in the shop rag catching fire, since the sparks hit the rag continuously. Be careful.

• 13. After the spacer is ground to .13" or very close, which is the difference in thickness from the old backing plate to the new mounting plate (and therefore, the measure of side bearing play), cut a slot in the spacer so that it just barely slides over the axle between the bearing and retaining plate. Or, if you got new axle bearings you could just install the spacers in between the bearing and axle retaining plate before you get the bearings pressed on. The notch is just so you can put it there without taking the bearing off (which would destroy them).

  If you used my method and cut the spacer from an old bearing, the spacer will be easy to place as you slide the axle in the rear end housing before you put the retaining plate on. Do not bolt the axle in yet. In fact, take everything off after you have made a mental note of where the calipers go on each side (they mount on the back side of the disk towards the trunk on the drivers side, and towards the front of the car on the passengers side. This was how it was on the Crown Vic, and makes e-brake cable routing easier).

  I don't trust my abilities nearly so far as to be able to do this, so I had a local machine shop make spacers. About $30

• 14. You'll need to fabricate some things here again. I used the existing stock early Mustang brake lines to each side past the spring perches, then tacked on a caliper hose bracket made from scrap steel (with my MIG welder) to adapt to the late model caliper hoses.

  Yes, you need rubber hoses so you adapt to the Crown Vic caliper hoses.
  Why do you need rubber hoses between the brake calipers and the rear axle you ask? Because there is some movement there in normal operation as the single sided calipers slide to adjust for wear, and so you can take off the calipers and replace the pads. You could clamp on brackets for the hoses instead of welding if you use good clamping techniques.

  The hose holder that connects to the brackets you just made is included as part of the brake hose. You'll see when you get them.

  After you have secured the fabbed brackets to the axle housing, visually check the hose routing and location for clearance and lack of sharp bends. Remember that the axle may be higher normally in relation to the car if you didn't jack the car up by the axle. Make sure not to block the upper e-brake adjuster slot on the disk brake mounting bracket!

• 15. Cut the existing hard brake lines and double flare with the new flares to fit the rubber brake lines. Bolt in the caliper hoses. If you didn't have enough hard brake line to work with (the stock rear end housing brake lines are a little short on the passenger side), consider buying new hard brake line and bending it with a tubing bender to fit.

• 16. Now stick on the disk brake mounting brackets and check out the e-brake lines. They route like this: Drivers side e-brake goes straight off the disk mounting bracket forward along the leaf springs to the middle of the car. Passengers side e-brake line goes 90 degrees, across the axle to the drivers side where it will make a gentle bend and go to meet the other cable where they attach together just ahead of the driver's side leaf spring perch.

  You'll need to fabricate two more things for the e-brakes.

  First, a mount to hold up the passenger's side cable as it goes across the axle. I tacked a bolt to the rear of the differential housing, right in the center, and bolted a little hose holder to it.

  Second, a bracket to mount the passenger's side cable about 2" behind the fuel line crossover (on my '68, this is about 6" in front of the leaf spring mount). This has to hold up to the force of the e-brake, which is several hundred pounds. It holds the outer part of the cable so that the actual steel cable inside slides in and out. I used a piece of 3/4" square steel tubing about 2" long welded at 90 degrees to the fuel line steel crossover cover (that three bolt thingy in front of the spring perch). I notched the tubing to fit across the bump in the cover, and welded an end cap on the tubing with a hole to fit the end of the rubber part of the cable. The cable end goes into this hole and the outer part is held there while the inner part goes to the connection between the two e-brake cables (the connection comes with the cable). This is more easily shown in a picture which I will send or place on a website when I have one available (volunteers?).

• 17. O.K. this is the last fabrication, I promise. Now take your stock old Mustang e-brake cables off, from the bracket under the driver's side footwell all way to the previous drums. That bracket, where the Mustang e-brakes adjusted, needs to have a steel holder for the end of the cable because we are converting to one cable for both rears instead of the two cables, one for each side, of the stock configuration.

  I used a strong steel collar about 1/2" OD and 3/16" ID. Something like a few nuts put together would work as well. Then I welded it to the bottom of the bracket. The e-brake end goes through there (after cutting off the swaged end), and then you'll add a bolt on or crimped cable end. This allows the stock Mustang adjuster to adjust this new setup. BTW, cutting e-brake cable is not as easy as it might seem. You can clamp it in some vise grips, and hack saw it, or cut it with the cut off tool, these are hardened steel cables. Wire cutters will not cut them!

• 18. Once you've gotten these parts fabricated and painted, stick them on, and this is how it goes: The passenger side cable should wrap around behind the axle, mounted there somehow, and make a sweeping bend and the end of the outer part (cable cover) should be clicked into the bracket that is welded to the fuel line cover (in front of the driver's side axle leaf spring mount). The steel cable comes out of that and joins the driver's side cable and goes to the front adjuster. The steel cable goes through the adjuster and after you pull it as tight as humanly possible, put on the cable end (I used two bolt on types, just to be sure). The adjuster should be all the way out when you do this so you can tighten it.

  I did this e-brake hook-up way differently.
  Because the caliper on the pass. side is toward the front, the e-brake cable pulls toward the rear. the stock Crown Vic cable for that side has a bent tube to help it make the turn along the axle.
  I pointed that tube up, then ran the cable along the frame, over the axle, through the channel where the original mustang cable ran, to the stock Mustang anchor. Anchor the sheath right there. The bare part of the cable is way too short , so I just cut the old Mustang cable's end off long enough to reach the stock Mustang adjuster, and clamped that piece to the Crown Vic cable.

  On the driver side, the caliper points toward the rear, so the e-brake cable pulls toward the front, just like the Mustang's. I used a new cable for the Mustang, cut off the brake end, and clamped on the end from the Crown Vic so the new cable can grab the lever that works the shoes. The Mustang cable will anchor to the Crown Vic anchor point, but you need to cut the little prongs shorter to compensate for the thicker anchor point. Then run the Mustang cable just like the original. My car is a '65, so it may not work with other years.

• 19. Now it's show time! Put the disk mounting brackets on, put the axles with the new studs in (making sure to get some grease on those new seals if you put them on!), and put the machined spacer carefully over the axle between the retaining plate and the axle bearing. This is a little tricky, but if you made the spacer from the bearing, it will fit perfectly and hold itself into place while you get the retaining plate bolted up.

• 20. Put the rotor hat over the axles. Note that the center hole of the disk doesn't quite fit the stock axle hub. It's a little too large to be properly centered by the stock 8" 28 spline axle hubs, but I don't feel much, if any vibration from this problem. Later I may get the axles turned and have them machine a spacer to properly center the rotor. This is what should be done.

• 21. Put the calipers, loaded with the brake pads in, and bolt them up to the disk brake mounting bracket. Now attach the hoses.

• 22. Tighten up the e-brake until the steel cable between the adjuster and mount isn't saggy. Then turn the rotors with and without the e-brake on and check for e-brake operation. Make sure the e-brakes don't drag! There are adjusters in the e-brakes (mentioned earlier), so you can adjust them for side to side brake balancing, but I'd adjust the cable as the main adjustment.

• 22. Now we must rid the car of any residual pressure valve. Loosen the rear brake line at the master cylinder and pull it out, making sure not to drop brake fluid on your paint. Use a screw to screw into the brass flange in the master cylinder and pull the flange out. Remove the check valve if one exists. If you are using the granada swap, with the front disk brakes for the granada, you'll need to get rid of the stock proportioning valve and plumb in an adjustable wilwood or similar unit in the rear brake line. I haven't done this yet, but it's necessary because the brakes will drag if there is any residual pressure valve in the system (disk brakes should not have any residual pressure valve). I know, I'm glossing over some things here, but this part has a lot of variables. I plan on using the stock disk/drum master cylinder from the '68 with the residual pressure valve pulled out of the rear brake side of the master cylinder with an adjustable proportioning valve mounted just under the dash inside the car. This will allow easier adjustment for brake proportioning.

• 23. Bleed the brake system, making sure to keep the shuttle valve centered (if you still have one in the car). There are tools for this purpose. If you don't care about your brake light being on, don't worry about the shuttle valve.

• 24. Test the brake operation with the car up and a friend pressing on the brakes. When satisfied, put the wheels on and test the system for leaks and e-brake operation. Then take a test drive and feel the benefits!

Added note: After doing this, I noticed some drag from the rear brakes. I thought it was some residual pressure valve but it turned out to be the emergency brakes. After a while, it went away (as the shoes were worn I suppose). The e-brakes still don't work well, but I think if someone were to convert to a foot type e-brake, like from the later model (>'71?) Mustangs, it would work much better. A pull out e-brake lever, as the stock early Mustangs had, is a poor activator! (mine work really well. The different routing may or may not help, but they do work well)

As always, I offer this advice for the benefit of those who are like me, and love to work on things like this yourselves. This information is as complete as I know, however this is only a guide, and therefore the user bears all responsibility for the use of this information. I do not claim it to be complete or completely reliable. Use at your own risk, and be careful! Brakes are safety devices and as such, should be built as well as possible. Good luck!

Best Regards,
Keven Coates
'68 five speed, four wheel disk Mustang