For c-clip rear Differentials.

GM and FORD

80's + 90's Ford 7.5, 8.8, and post-1964 GM 10 and 12 bolt.

Step 1.  Open the box:         

Step 2.  Check the components to the parts list enclosed in the instructions.

Rear kit "Package" with calipers and emergency brakes:

OR rear bracket set with mounting bolts: 

Step 3.  Read all of the instructions carefully.

Step 4.  Remove the old brake drum, unbolt the brake backing plate from the housing-end, disconnect parking brake cable, and disconnect brake line.

Repeat for the other side.

The backing plates will still be trapped by the axles.

IF YOU HAVE A FORD 9 INCH or DANA or any other axle that DOES NOT USE C-CLIPS skip to step 9.

Step 5 to step 8 are for the c-clip axles ONLY-  Ford 7.5 8.8,  and GM 10 and 12 bolts after 1964

Step 5.  Remove the rear differential cover and drain the oil:

Step 6.  Locate and unscrew the Pin/Bolt that holds the center pin in place:

Step 7.  Remove the center pin:

At this point, it is  IMPORTANT  to keep the spider gears (the small bevel gears that ride on the center pin you are removing) (those are the ones that keep the right side axle gear joined to the left side axle gear) in their proper alignment with the end gears (the small bevel side-gears on the axle ends).  The safest thing is to avoid turning the axles or the carrier while the center pin is out of it's place.- Or at least if you have to turn the carrier a little, make sure both axles follow along so as not to move the spider gears out of place.  That way the gears won't wander off their alignment. 
If they do come out, it's not a disaster, just more work you could have avoided.  I'll put up a link to more illustrated instructions on how to put them back, but it may be a little while before I get the time ...

Since C-Clip axles do not use the wheel bearings to hold the axles,  the axles are  held in by a ring-clip or C-Clip that rides in a groove in the axle. 
When the C-Clip is in place,  it prevents the axle from being  pulled out.  When the  center pin (the one you just removed) is in place, the center pin prevents the axle from being pushed in.  This is what  holds the axle in place and determines axle end -play.

  Step 8.  Push the axle inward toward the center of the car. This moves the inner c-clip out of the pocket in the side gear where it was trapped, and allows you to slide the c-clip off the groove of the axle. The axle is now free. You may slide it out of the housing. Repeat for the other side.

They should slide right off.

  Most conventional installations will use the calipers in a position slightly above and to the rear of the axle housing
(10 o'clock and 2 o'clock). Some will be mounted at 9 o'clock and 3 o'clock.

Some GM models will have a staggered-shock arrangement that will require one bracket to be mounted in FRONT of the axle.  No problem- Just flip the bracket over and mount it in the forward location.  

In that situation, you will need to use either two left side or two right side calipers instead of a Right and a Left caliper.  That will keep the bleeder fittings at the top. 
 1985 Cad Seville rear calipers come in a Right and Left. I prefer the Seville calipers for the "traditional" cars.
  Mid 80's Camaro rear calipers are actually two LEFT side calipers. Many Camaro have a staggered-shock arrangment that requires the passenger side caliper to be mounted in FRONT of the axle while using another LEFT side caliper on the right side. 

Step 11.  Return the axles to the installed position, and put the c-clips in place. Put the center pin in it's normal location to hold the axles in the place where they will normally run. If you skip this step, and fail to have the axles in their proper location, you may have to re-adjust things later.  Save yourself some work by taking the few extra steps right now.... Install the c-clips and have the axles in their proper positions so you can check caliper+bracket location.. 

Step 12.  Mount the rotors.  Just for now, use washers and lug nuts threaded on backwards to hold the rotors to the axles.  Make sure the rotors run true, and that the axles are not bent. You may need to change the studs on certain models. Look closely- You may also find a burr or other irregularity on the axle flange that will need to be filed smooth. This will let the rotor lay flat on the axle and run straight. 
     One suggestion-  Some rotors are made in one piece with a cast iron "HAT".  Others are made with a thin stamped steel center section (HAT) that is cast into the rotor for a one-piece effect.
The cast iron "HAT" is thicker than the stamped one, and is much better for use in these situations where the wheel studs are counted on to locate the rotors.  I use CarQuest rotors, and ask for the ones with the prefix "P".  At CarQuest the "P" means rotors with the cast iron center HAT.

The rear rotors to use for the 5-lug, on 4-1/2 inch "regular Ford" bolt circle, use the 1985 Lincoln Mark7 rear rotors. ****
 The rotors to use with the early+ mid 1980's on up Ford Mustang and others using the 7.5 and 8.8 rear ends- For the 4-lug (4-1/4 bolt circle) use the 1988 Turbo Coupe rear rotor.
 I have been told by some Mustang owners that they have switched from 4-lug to 5-lug by using TWO Driver side Ranger axles in their Mustang housings- I have not done that myself, but it is aparently a popular swap.

The rear rotors to use with our 10 and 12 bolt GM brackets are 1980 TransAm rear rotors for the 4-3/4 lug circle, or 1978 Cadillac Sedan DeVille rear rotors for the 5 on 5 lug circle.

Step 13.  Test fit the calipers with brake pads in place. This will tell you if you need to move the brackets to match the rotor location 

Step 14.  Now that you have the old drum brake parts removed, and the brackets in the correct position, you can reinstall the axles and put the center section back together if you haven't already done that.

Step 15.   If you have removed the rotors to install the axles, now is the time to put the rotors back on the axles.

Step 16.   Put the brake pads on the calipers,  put the calipers on the brackets, and slide the guide pins into place to hold them all in place over the rotors.

Step 17.   Hook up the hydraulic brake lines. While many cars used a flex hose for the calipers, the Cadillac factory used a large loop in the steel line and a small brass fitting at the end where the banjo bolt threads into the caliper.
 
     Note- On my cars, I used a plumbing method similar to the Cadillac method by making a small coil in the steel line on top of my axle to allow for caliper movement due to pad wear. The thing to watch for in that situation is trapped air bubbles at the top of each coil. 
     If you bleed the lines very gently (some people simply crack a fitting and let it dribble out), you may still have trapped bubbles at the top of each loop.  I bled mine simply with a good foot-pedal pressure and opening the bleeders for a "robust" gusher of fluid. That seemed to be good enough to push the trapped bubbles along the lines to be expelled.  I had no problems with air bubbles even with the coils in my brake lines.  Of course, you could use flex hoses and no coils in the line..
Brake Hose- one suggestion-  Wagner part # F97661  or most any front or rear hose with the typical "banjo" fitting.
 
Step 18.   Now for the e-brakes.    
      Use 1985 Cadillac Seville rear calipers with built in parking brakes. GM front "Metric" calipers (mid 80's) will fit the brackets, but front calipers do not have the built in parking brake. The same GM cars will supply the pads, guide pins etc.

******** If you choose to buy the incidental parts (e-brake levers, return springs, etc) from a junkyard GM rear disc car you can save on price.
 HTTP://SELECTCORE.COM   has them at a good price.
 
If you want NEW GM parts (some may or may not remain available NEW), then here are the GM part numbers-
Return Spring Bracket and Bolt--
GM-18005312-Left Side
GM-18005311-  Right Side

Return Spring (need 2) - GM-180055822
OR you can use what I use- #68 spring from ACE HARDWARE for about 80 cents each.

E-Brake Levers-
GM-18003044-Left
GM-18003045-Right

10MM Banjo Bolts.
Brake Hose- Either mid 80's Camaro, Cad or Wagner part # F97661

 Lokar has a universal parking brake cable kit for around $100.00 if you need a new set.
Using these OEM parts is the lowest cost way to get rear disc brakes if you compare to the other brake suppliers.

Now the questions about residual pressure valves--
 
      Many of you will already know that the traditional drum brake systems use a valve inside the master cyl that
traps about 10 or 12 lbs pressure in the system when the brakes are not being activated, to prevent fluid drainback
and keep the brakes ready to act.  That has worked great for many decades.

       Disc brakes do not like that much Residual Pressure in the system because they don't have return springs or an
internal mechanism to retract the piston. 
      It is widely accepted that 2-4 lbs residual pressure is ideal for conventional disc brake calipers.
 It is enough to prevent fluid drainback, and in most cases keep the  brake pads in contact with
the rotor, partly to keep the rotor clean, and partly for instant response. For disc brakes it is desirable to
 keep the brake pads in contact with the rotors.
     Using 10-12 lbs residual pressure will, in most cases, cause the disc brake pads to rub the rotors a bit more
than is wanted.
     Conventional wisdom says that for a front-disc/rear-drum car you should use 10-12 lbs  residual pressure for
the drums in the rear, and 2-4 lbs for the discs in the front.

      OK so far.

     Now when you want to add rear disc brakes, which would give you 4 wheel disc brakes, it would seem to
follow that you would want 2-4 lbs residual pressure for both the front brakes and the rear brakes.. right?

      NOT SO FAST! Hold your horses!

        The "conventional wisdom" that tells you to use a 2-4 lb residual valve for disc brakes doesn't
 take into consideration the fact that not all calipers are the same.
       The usual front calipers do not have any return springs or other provision to retract the caliper piston
the brake pedal is released. The usual 10-12 lbs residual pressure in a drum brake system is easily overcome
by the drum brake return springs.
       Since the usual disc brake caliper does not have the springs, the 10-12 lb residual pressure will keep the
disc brake pads dragging when the brake pedal is released. That is why you need to change to 2-4 lbs
when changing to discs.
       
     SOUNDS GOOD. When using FRONT calipers on the rear without e-brakes, that is OK.

        BUT---  What about the Cadillac REAR calipers with the built in e-brakes and internal self-adjusters?

  Don't they have return springs, and a retracting mechanism that retracts the piston?
               YES. 
  And that can save you a bit of work.
        When you use the Cadillac rear calipers, you will need the 10-12 lbs residual pressure that is
found in the usual drum brake system.
        If you follow the conventional wisdom of taking out the 10-12 lb valve and installing a 2-4 lb valve,
you WILL end up with a low brake pedal that will require one or two pumps on the pedal in order to
bring the pedal up to a normal height.
         
          When using the Cadillac rear calipers, you should leave the stock front-disc/rear-drum master cyl alone.                                     I like that situation. It saves a lot of work changing the pressures in the system.
    
         Just use the Cad rear calipers and don't bother changing the stock master cyl and valves.
        They are already just right the way they are.
     It's when you try to use non-e-brake calipers (front) on the rear that you complicate things.

******************************************************
**** For those who NEED to change the residual pressures ****
******************************************************

MOST disc brake master cyls for a front disc rear drum vehicle will have a 2-4 lb residual pressure valve near the outlet to the front brakes, and a 10-12 lb "RP" valve at the outlet to the rear line.

This is a close up of the outlets on a DUAL MASTER CYLINDER.

If you use a SINGLE-chamber MC (enjoy living dangerously?)
(there is a reason duals are required on new cars)
you must disable the RP valve INSIDE the master cyl.
On a Stude, it is the strange looking round, slightly cone shaped disc with some perforated holes in it. Simply running a small drill bit hole through the membrane inside it will prevent it from holding residual pressure in the system.
This shows the location of the Residual Pressure valve inside a typical SINGLE master cyl.

You will then need to install an inline 2-4 lb residual pressure valve
in the steel line running to the disc brakes (non-e-brake type),
and a 12 lb RP valve in the steel line
running to the drum brakes (or Cad e-brake calipers).

($17 at Summit Racing and other rod shops)
 WARNING-- skipping this step of installing the RP valve(s) will result in a low brake pedal that will often need pumping to make them work correctly.

IMPORTANT!! Make sure that ALL existing brake lines, hoses, and cylinders are in excellent working order, and are recently installed.
 Using 10 year old steel lines with hidden corrosion, or 10 year old rubber hoses with simple aging, is unnecessary risk taking. ALL reasonable systems and parts will easily handle a booster and discs, BUT if you have any marginal parts that may be near failure, it may show up now.
Please check the entire system and replace all questionable parts right away.

         For a street car- save the extra work, and be legal--  use the recommended Cadillac calipers.