Rear 11.65" Cobra brake install

The reason behind this choice is threefold. First, I can get replacement parts anywhere. second, it is very light weight with the P. brake built into the calipers, this makes a big difference when you are trying to setup your suspension (unsprung weight). Lastly the 11.65" rotors have exceptional stopping power.
This is a combination of two kits. The bracket kit supplied by
North Racecars Great group of guys that do a lot with the Factory Five Cobra kit cars. This is designed to be able to use the stock Ranger 5 lug axles. I decided to go with Superior axles. I've had real good luck with Superior products, and Summit Racing had a good deal on them. If you look close in this picture you will see I have added a ring to the end of the axle in order for the rotors to be hub-centric. If you buy the axles from North Racecar, they will come setup to make the rotors hub centric. This is very important!

The instructions include the part numbers for the splash shields

and also for Parking Brake cables, and brake hoses. This kit was designed for a Cobra kit car with a tunnel mounted hand brake. So it takes a bit to make the recommended brake cables work with the stock Mustang parking brake system.
I used the '65 Mustang cable bracket from NPD, and routed the cables lower to keep a straighter pull.

When I strip the car down I'll move the stock brackets down to keep the factory look.

The cables are about 9" short of the stock length. I extended the "Z" bar by adding a coupling nut and threading a piece of 5/16 cold rolled rod stock then quenching the stock. To keep the whole thing from bouncing up and down I used an eye bolt with an aluminum stand off. And to eliminate the rattle between the eye bolt and the rod extension, I used a piece of heat shrink tubing over the rod itself.

The parking brake works exceptionally well. I'll go ahead and fabricate the correct length 1 piece "Z bar" and a nice looking billet brace when I re-do the whole car. This was more for a mock up, but it works so well, I'm leaving it for now.
The calipers and rotors came from
Stangstore.com These guys had great prices and even with shipping was cheaper than I could have picked them up anywhere else.  Unfortunately I think they are gone, as the link doesn't work anymore.  The drilled and slotted rotors are FRPP products, and match the front discs.
The calipers came loaded with stock pads.
I used the stock steel line, and the stock Fox body center brake hose. I welded a coupling nut onto each side of the rear axle housing to mount the outer hoses to, and cut the excess bracket off to clean it up. You can see the way the caliper hoses mounted up by looking at the very top picture. Came out very clean.
In order to use the Fox body center brake hose you need the fitting that attaches to the body. This fitting is no longer available at Ford, so you will need to pick one up at a wrecking yard. Took a little work with a die grinder to open up the mounting bracket, and looks like it is a factory piece. In order to center the hose for free movement up and down without getting stretched you will need to bend the bracket that mounts the hose to the rear end, until the hose is level with the body mounted fitting. This is very important. If you don't do this you will break the hose!

At this point its just a matter of adding a proportioning valve before the master cylinder. I opted for an adjustable one from Summit racing. You can add a lot more rear bias than you think! And they look pretty nice sitting inside the 17" wheels.

Building the differential from a bare housing

Instead of going over a complete differential build, I thought I'd just show a couple of options I used, and write about what it took to start with a bare 8.8" housing with no shims. All the other information has been written up so many times it's not even funny.
Here is a shot of the rear end setup and the girdle which in my opinion is one of the key elements to making the 8.8" work.

I used a Detroit True-trac 31 spline torsen carrier unit. I chose the True-trac for it's torque sensing and smooth roll in. This is especially desirable for road course work. There were two versions, an old and a new version. Make sure to get the new version. From what I've read, there was an issue with the original version breaking the end cap bolts. The girdle In the picture is an FRPP version. This uses studs that push up against the carrier bearing caps to support the caps from moving. Just about everybody and their uncle makes girdles for these rear ends, so..."what ever flavor suits you". I like the idea of having a magnetic plug at the bottom.
The 8.8" rear is a factory cartridge type. all the shim stacks are setup based off a jig. That's great until you end up with a housing and no shims. Fortunately, there is some great information available between the Mitchell and Chilton professional reference books. I made a stop by the local library and got all the information I needed to set up the shim stack. The key is knowing that the carrier bearing preload is between 0.010" and 0.012". In order to set this up, stand the axle housing on its end, Use a cast shim under the carrier bearing on the bottom side, then shim the top until a 0.010" feeler gauge just drags through. Measure your total shim stack to include the cast shim on the bottom, and add 0.022" to the stack. That is your total shim stack needed to get the correct bearing preload. divide by two as a starting point and put half in each side. Then adjust based on gear pattern and backlash. The other interesting bit of trivia, is that when going to 3.55 gears, and using FRPP gear set the pinion shim usually ends up at 0.034". Using nothing but a dial indicator for backlash, and gear mesh compound I was able to set an excellent pattern with the backlash exactly in the sweet spot.
I did two things a little different. One I picked up an extra set of pinion bearings and using a die grinder opened them up just enough that they slip on and off the pinion. Second, I ditched the crush sleeve for a spacer and set of shims, and did all my set up with a used pinion nut. After setting up the carrier total shim thickness, I started with 0.034" pinion shim. I ended up at 0.035" with an excellent gear mesh and perfect backlash.
The proof was in the car. My first few sets of runs the rear end temp was right around 275*F. After the first two heat/cool cycles, the rear temp started coming down consistently over the next ten cycles to where now it runs about 190-ish. And the rear end is very quiet on acceleration and deceleration, just like it should be. I've got about 1,500 miles now. Everything bedded in very nicely, and it looks ready for a long life.
The bottom line is, you can spend all this money on special measuring tools, build jigs, etc. What really matters is bearing preload, gear pattern, and backlash. For that you need some basic tools and a little common sense.

Back to main page