04BlueGT

Hey guys, I just bought this car to prep for my daughter to drive in a couple of years. I really don't want the expense and hassle of converting to 5 lug, since the 3.8 is staying (for a while, anyway).

I want to update the brakes to 4 wheel discs. I found a site that offers rear axle mounting plates that allow you to bolt on the rear calipers from a 99-04 onto the 8.8 or 7.5 rear (I have the OEM brakes from my 04 in a box).

I figure I need a new master cylinder (say, '93 Cobra) and proportioning valve.

The real questions are, 1) can I bolt the newer GT front calipers to the '83 spindles and 2) does anyone make a 4 lug rotor to fit the 99-04 calipers?

motorman524

The newer calipers will not work with those spindles. I'd upgrade the booster along with the MC. Made a huge difference for me.

projectresto83

The first thing you need to do since you want to stay with a 4 lug setup is to upgrade to 87-93 5.0 spindles, master cylinder, and brake booster.....

Then upgrade to SVO calipers w/ steel piston, stainless steel caliper inserts, hawk pads and shoes, stainless steel brake lines.

mustangGT86_05

Correct, and I swapped to a tbird turbo coupe rear end which is disc, but a little wider. Swapping it with the 79-86 mustangs is different than doing it for an 87-93, in the tech articles I have more info on our year range swap. It will also most likely end up cheaper for you than buying a kit.

I also did as mentioned with the svo calipers, and yes requires a spindle swap. It isn't too difficult to do. I haven't upgraded my booster and can have a lot of braking force potential but I also have strong legs. I also used an svo master cylinder which is perfect for the 79-86 models with the largest bore you'll find which will help compensate for the large svo calipers.

04BlueGT

UPDATE: I put new (reman) calipers on today in an effort to improve the braking. I tried to lock up the brakes and the results are not good. The rear drums locked up almost immediately, as they should. The front was different. The right front locked up for the last 10 feet, but the left front never did. At this point, I think the proportioning valve needs new O-rings. Also, how can I tell if the booster and/or master cylinder are bad? The pedal feels weak, but I'm used to my '04 with Cobra brakes.

projectresto83

Well the brakes just suck all the way around..... If the booster was bad the pedal would feel rock hard and not stop very well (compared to normal). If the MC was bad the pedal would have pressure then start sinking to the floor as the fluid bleeds back past the seals into the resevoir or just feel completely spongy even though you have bled and bled...(if you know you have done it properly).

enix187

Also fixing the near thirty year old suspension will make a difference even with braking, nothing done to the brakes will help much if the car dives hard enough to scrape the bumper (not saying it does just a suggestion) it would be easy enough to put late model gt front brakes and a lincoln rear, then the a master cylinder with a bigger bore should decrease pedal effort while keeping you locking the brakes as easily, also braded steel brake lines

04BlueGT

I had the same thought about the weight transfer. The entire suspension is shot. I'm accumulating parts and polyurethane to take care of that now. But I'm still not convinced the proportioning valve is working correctly. The front rotors don't look "clean" from wear. It's like I'm not pushing enough pressure to the front to remove the oxidation. I don't know if that's attributable to the stock rotor and crappy pads or a lack of clamping pressure. What do you all think?

P.S. My daughter already purchased 4 lug wheels, so a 5 lug conversion is out of the question.

projectresto83

Sounds like your MC...when you replace it be sure to replace your wheel cylinders to if you haven't already. If they are the old ones a new MC will blow the seals.

04BlueGT

I considered that, but I don't have any leaks and the lines don't seem clogged either. I'm still thinking suspension and proportioning valve are bigger culprits.