Brake Upgrade For 89 Gt Keeping 4 Lug

Discussion in 'Fox 5.0 Mustang Tech' started by plork66, Jan 21, 2014.

  1. I have read about the brake upgrades swapping rear ends with 94-98. I have also read about the T -bird SC rear end swap. Just wondering first of all would I be better off in the long run to do the 5 lug rear end or stay with the 4 lug. I would like to keep my GT as stock looking from the out side appearance as I can. Second I really don't want to start swapping parts, retrofitting, and having wheel clearance issues especially when the potential problems are dealing with my brakes. My GT has 54k original miles and I have replaced both rear wheel cylinders and but new brakes on, and actually I don't have any issues with the drum brakes they are easy to work with. My issue is that I would like to slowly start getting my 89 into the 21st century. If I want to go faster I feel I should be able to stop faster. I also don't have problems going to the bone yard or buying a car for parts if everything will match up. I just don't want to start tearing my perfectly fine running 89 up and start having issues. I have seen some rear disk brake kits out there and they aren't cheap. Just want an opinion about going 5 lug or staying 4 lug. Also it seems the SC 4 lug will bolt right under, but the 94-98 rear definitely will and calipers can be upgraded but 5 lug and 17 inch rims. The cost of new rims and tires would probably offset the rear brake conversion kit? My 89 has 91 pony rims. I like the upgrade to 16 inch, I don't think 17 inch rims will clear.
    Reynaldo rivera likes this.
  2. I used 4 lug TBird stuff on the rear of my '88vert.

    I also used "SVO/Crown Vic" larger 73mm piston calipers up front to increase the clamp on the front rotors. Very cheap and bolt right up! Less than $20 each at Autozone.

    I also used an SVO style master cylinder and gutted the internal proportioning valve. Again very cheap at Autozone!
    Then I added a firewall mounted adjustable proportioning valve to move more pressure to the rear.

    My car stops pretty damn good for a simple, budget minded "Cheap" 4 lug settup.
    Grabbin' Asphalt likes this.
  3. Got any build pics??
  4. The 94-95 Mustang GT Master Cylinder is more ideal if using the 73mm calipers up front, and the 45mm T-bird calipers out back. It also retains the low brake fluid switch function, and is much easier to swap into a Fox mustang.

    The SVO MC is required if you install the 73mm front calipers, with the 54mm rear SVO brakes. With the 45mm rear t-bird calipers, a slightly smaller bore MC is ideal.

    Short of an aftermarket front brake kit, this is probably the best you will get

    73mm front calipers
    rear Thunderbird Turbo Coupe disk brakes
    93 Cobra booster
    94-95 GT Master Cylinder

    You're still looking at anywhere from $500-1000 in parts. You can modify the rear disk brake offset to be the same as the stock drum brakes, but that requires new axles and caliper brackets. More $$$

    At the end of the day...this isn't gonna be cheap. SO determine your final ultimate goal, and research!
  5. Gosh, its been 8-10 years since I did this. I don't have any build pics but can remove a rear tire and take a pic if you like.
  6. Been there and done that! With success! :nice:

    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, 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.
    When you install the axle assembly you will need to leave the bolts for the control arms only finger tight. Once the axle and all the control arms are in place, put jackstands under the rear axle and under the front A arms. Level the car as best you can while it is on the jackstands. Then and only then tighten down the control arm nuts and bolts to the factory specs. This assures that there is no preload to position the axle up or down, it is preloaded to normal driving height.

    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 for details and pictures.

    See 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 axle swap parts list:
    87-88 T-Bird Turbo Coupe Rear axle
    94-95 Mustang Master Cylinder with reservoir
    Brake line Adapter fittings
    3 line to 2 line brake fitting kit
    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 attaches 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.
    Fixing the added axle length problem:
    If the extra width is a problem for your wheel and tire combination, North Racecars makes some rather expensive brackets ($160 +) which allow you to use the stock axles. See
  7. I would not recommend 73MM calipers unless you change the MC. The larger calipers will create a softer pedal and not help your stopping distance. The cheapest and best bang for the buck 4 lug brake upgrade IMO is the MM brake upgrade kit for about $250. You get

    • SS hoses
    • SS caliper bushings
    • upgraded disc pads
    • upgraded drum shoes

    I've installed this kit on two fox body cars and just bought it for my current one. It make a noticeable difference in stopping.
  8. No extra work on account of me, but I've been quietly reading my options for later projects.
  9. 5-lug is worth it just for the options it opens up with wheels and tires. Things are pretty darn limited in 4-lug anymore.
  10. Check out maximum motorsports 4 lug upgrade. Comes with steel caliper sleeves, ss lines, larger drum pads, and hawk front pads.

    Edit: oops just saw someone already suggested that . That's the route I'm going next month.
  11. let us know how they work for you?.....i was thinking of trying those...
  12. Will do. It's gonna be once I get my tax money but I'm on here frequently so ill definitely report back.
  13. I realize that I may be entering the game in the bottom of the 9th with 2 outs, but I am in the process of trying to get my hands on a 87-88 TC rear end. I am from southern IL, @ 20 miles from St. Louis. Every yard I try gives me the chuckle and "good luck with that". I have nothing but time and I will keep looking. I like the idea of finding the part and getting it prepped , getting all needed parts and help lined up, and then making the switch. Just wondering if anyone out there fairly close to the St. Louis area or parts in between my have some knowledge of the whereabouts of an 87-88 TC sitting around that would like to be a donor for my project?
  14. thanks for the information!!!!!!!!
  15. I had same comments up in the northern part of the state. Had no luck finding any.
  16. View attachment 120045 Rear disc brake swap
    This seems to be a topic with 2 views. I presently have an 89 GT that I will soon be upgrading to rear disc. The general consensus is to go 5 lug to get the Cobra brakes. I presently have 91 pony rims on my 89 and they look and function fine. I have located an 88 T.C. in a junk yard , sight unseen , that I could have shipped because it is @10 hours away. Just wondering if the rear upgrades sold at for example LMR for @ $800 or so is the better route. I have never done any type of brake swap so I am not sure about the labor involved. I just was wondering if replacing the entire rear assembly would be less labor intensive. I am a plumber and will leave the brakes to someone else, just wanting to know which route. I realize also that the T.C. Will have 3.73 gears, this one is an auto., which is a needed upgrade also. I viewed some rear disc upgrades and since the axles need to be removed it seems if the LMR route is done that would also be the time to do gears. I think, pending the T.C. Rotors and calipers are not destroyed, the cost would be cheaper for the T.C. The guy is asking $400 for the complete rear axle assembly, so not sure what the labor involved between the 2 will consist of. Anyone have any ideas?
  17. The 4-lug rear disk upgrades you typically see are the turbo coupe rear disks brakes, but sold woth fox width axles and brackets designed for stock rear track.

    With the newest turbo coupe in the boneyard being 25 years old, good used parts are hard to find. The decision really depends on what shape the rear you find is, and the mechanical abilty you possess (or willing to pay for)

    There are many options out there for brakes on these cars
  18. just so I am 100 percent clear, can I use the the axles in my stock drum brake 8.8 rear to do the disc brake 8.8 rear swap?

    Are there any junk yard axles I can use to do this? Or am I stuck with aftermarket axles?
  19. I thought all the ranger/aerostar axles were 5 lug?
  20. The calipers on TC's are often frozen on the caliper slide pins, or the E brake mechanism is frozen. For this reason, plan to swap the TC calipers for remanufactured units that are fully loaded with caliper mounts, pins and pads. That adds $40 per side to the TC swap. Small cost for peace of mind. See Advance Auto Parts Part No. SLC277 & Part No. SLC278