The rear axle & disk brakes are another junkyard item:
Do the 87-88 T-Bird Turbo Coupe rear end swap!
Auto trans 87-88 Tbird Turbo Coupes come with 3.73 gears and manual Turbo Coupes come with 3.55 gears. Cost is $125-$300 for the rear axle. Add another $100-$200 or so to complete the brake upgrade.
I choose 3.55 since I do more highway driving. Both ratios have 10 5/16" disk brakes with vented rotors as standard equipment.
It takes 2 guys the first day to get the old rear end out and the new one bolted in place. It takes 1 guy another whole day to do the brakes.
You will need a several sets of fittings, I recommend that you get them from Matt90GT's website, 87-93* Ford Fox Body Mustang Brake Upgrades. Read Matt's instructions thoroughly, everything you need to know about the brakes is all there. You need to be patient and follow all the internal links, and there are many of them. You will need 2 fittings in the rear to adapt your old brake tubing to the TC disk brakes. The fittings go between the steel tube and the caliper brake hose. You will need another set of fittings to make a 2 port to 3 port adapter. To make life simpler, just buy the kits from Matt. You could piece them together, but it's not worth the time unless you work at an auto parts store with all the fittings ever made.
You will need to drill the quad shock mounting holes 2” below the holes drilled for the Turbo Coupe mounting points. The bolts are metric, so don’t loose them or the nuts. A 15/32” drill should be about the right size unless you have access to metric sized drill bits. Going without quad shocks is not an option unless you have aftermarket parts to soak up the wheel hop.
You will need a proportioning valve, Summit has one for $40 + shipping.
You will need a kit (FMS makes the part) to gut the stock proportioning valve, Summit also has that, about $10.
You will need a new master cylinder, see Matt's site and make you choice. I used a 94-95 Mustang master cylinder. Note that rebuilt 94-95 Mustang master cylinders do not come with a reservoir. That means a trip to the junkyard and some more money spent.
Your brake pedal may be very hard and almost impossible to lock up the brakes. I had to replace the front calipers with 73 mm calipers from a 91 Lincoln Mark 7 to get the braking performance up to par.
Bleeding the brakes will require 2 people and some coordinated effort. I don’t recommend using you wife or girlfriend to pump the pedal – they get offended when you yell at them. I used a homemade power brake bleeder constructed from a garden sprayer and some fittings from Home Depot. It cost about $25 and was worth every penny. See how hard is it to bleed brakes? - Mustang Forums at StangNet for details and pictures.
See Mustang Central.net FMS M2300K Brake Install for help with the emergency brake. The red words link to some very useful photos on how to modify the handle. The stock setup tends to lock up and not release properly.
All in all I have been very pleased with the results.
Turbo Coupe parts list:
87-88 T-Bird Turbo Coupe Rear axle
94-95 Mustang Master Cylinder with reservoir
Brake line Adapter fittings 87-93* Ford Fox Body Mustang Brake Upgrades.
3 line to 2 line brake fitting kit 87-93* Ford Fox Body Mustang Brake Upgrades..
Proportioning valve, Wildwood 260-8419 Summit or Jegs
Kit to gut the stock proportioning valve Ford Racing M-2450-A Summit or Jegs
Reuse stock brake booster – no changes needed with the parts in this list
73 mm front calipers from a 91 Lincoln Mark 7 (two calipers) local auto parts store
Emergency brake cable parts: Summit or Jegs or Late Model Restoration
79-92 Mustangs use: M-2809-A* Parking Brake Cable (need 2)
93 Mustangs: use 93 Cobra Ebrake cables.
All years use: M-2810-A* Parking Brake Cable (short cable that attachés to the parking brake handle)
I recommend that you use reman calipers and use the calipers from the Turbo Coupe axle for cores to return. The parking brake mechanism and the caliper slides tend to lockup and freeze
Identifying a Turbo Coupe rear axle:
1.) Measure the rotors - a TC disk brake uses 10 5/16" vented rotors.
2.) Measure the length of the quad shock mount arm and compare it to the mount on your existing stock axle. The TC quad shock mount arm is about 8" long if I remember correctly.
3.) Measure the distance between the axle flanges and compare it to stock. The TC rear axle assembly is 3/4" wider per side, or 1 1/2" wider for both sides.
Five lug Turbo Coupe conversion:
Use the 94-98 axles Mustang axles. Use 1990 Mazda MPV 3.0 V6 front rotors (10", 5 lug x 4.5" pattern, 2 7/16" offset ). While you are at the auto parts store, set a TC rear rotor side by side with the Mazda rotor and they are the same except for the offset.
The next step fixes the offset problem:
Use a Maximum MotorSports 1/8 spacer (MMWS6, Maximum Motorsports, the Latemodel Mustang Performance Suspension Leader! ) between the inside of the rotor and the axle flange. The spacers may need to have the OD machined to fit properly. The stock rotor offset is 2 5/16" and the Mazda rotors are 2 7/16" offset. The 1/8" spacer puts the rotor back dead center alignment with the calipers.
The Mazda rotors are under $30 each, and I have seen them for $20 each. The MM spacers are two for $30 + $9 shipping. So the entire package costs $99. That saves $41, which most of us could find a very good use for.
Why not just swap the brakes and rubber lines, instead of the entire rear?
You can slot the brake mounting bracket to slip onto the Stang rear, behind the flange, and cure your offset problem without buying adapters. You would have to remake the lines leading up to the rubber lines, it seems to me, but not too big a deal. Unless you just want the gears... Then it's different. You can swap your axles and brakes to the rear and get the gears if the brakes aren't your goal.
I have a 3.55 TC disc rear laying up right now. When things slow down in a month or two, my son is putting the 4 lug discs on his car, and I am putting the 3.55 gears and housing in mine. The axles are too long for a Stang and useless.
The axles are 3/4" longer per side. That is the same length as the 94-95 Mustang 5 lug axles. They will work OK with stock wheel offsets as long as you don't get crazy with the tire size.
BTW: If you swap the brakes, I would use the TC proportioning valve block and a 94-95 master cylinder.
That is what I would do anyway... Everyone has a solution that is a bit different than the others when it comes to P-block.
I would probably use the Cobra master as well, the GT those 2 years is different, and the Cobra is supposed to be an upgrade for the GT.