4 Lug Limitations

On the drag racing end I have seen a set of 4 lug axle run 5.70-5.80 in the 1/8. This was on a 306 Vortech supercharged car with an auto. I don't know how long I would trust that setup. Put this car ran it for years with not problem. But for you setup I don't think you would have any problem with the 4 lug axles.

31 spline mosers . . . 5.60s @ 121 in a 2700lbs car

4 lug is fine you just cant try drifting and have limited wheel selection, you can upgrade the rear to disc and keep it 4-lug

You must really like your wheels, i'm the same way with mine...

ive seen a car in the 9.20 range with 4 lug.

Informant736 said:

Who makes 4 lug rear disc conversion kit?

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use factory stuff . . .

My 86 Gt is 4 lug 4 wheel disc
you use hardware from an svo mustang to do the swap. I used everything off an 86 svo. Stops great alot better than the crap drum brakes

svo is 5 lug.
I put 700+ hp through my 4 lug Power is not an issue.
Its wheel selection and cost of brake up grades

Do the 87-88 T-Bird Turbo Coupe rear end swap- 4 lugs and an easy converion to 5 lug when the time comes...

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” 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, http://www.svo73mm.cjb.net/. 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 http://forums.stangnet.com/showthread.php?p=6143048 for details and pictures.
See http://www.mustangcentral.net/tech/brake.html 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.

Mustang5L5 said:

SVO's are 5-lug.


T-bird turbocoupes and '93 Cobras are 4-lug

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saleens are also 4 lug discs out back but I think they used lincoln? stuff?

not sure on where they sourced parts from but I know they are 4 lug discs

50 resto has a kit from SSBC for a complete 4 lug rear disc conversion kit w/new master cylinder, but it costs $699

Informant736 said:

jrichker - thanks for that post just about answered everything i needed to know.

Hopefully my last question on this is, I have a rebuilt 8.8 with 3.73's in my stang. In the links above it says that the tbird rears are 3/4" wider, i would rather not have to swap out rears, could i just pull the brakes off the tbird?

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You would be missing the anti moan brackets. The caliper design requres the longer axle to center the caliper over the rotor. It is possible to use stock axles if you cut the caliper mount brackets, mount them on the inside of the axle and then weld them back up. Email Ranchero5.0 since this was his fix to use stock axles.

There are other options as well, see http://www.svo73mm.cjb.net/. for the best information you can find on Mustang brakes.