About the Video
1979-1993 Mustang 5.0resto 4-Lug Rear Disc Brake Conversion - Review & Install
Check out our YouTube channel for even more tech tips, installation videos, how-tos, and more. The best place to go for anything Mustang related!
Published on 2016-09-27
Ditch the drum brakes on your 1979-1993 Mustang with this 5.0 Resto 4-lug disc brake conversion! This is the most complete 4-lug disc brake conversion you'll find on the market! This is a great conversion for someone that wants to retain their 4 lug wheels but upgrade to rear disc brakes.
It has everything you need including the dust shields, proportioning valve, lines, calipers, pads, brake lines, E-brake cables, rotors and hardware. The factory 4-lug axles are retained for an easy installation.
Fitment: 1979-93 Mustang
1979-86 Item # LRS-23207986-K
1987-92 Item # LRS-23208792-K
1993 Item # LRS-232093-K
What’s up everybody? Landan with LMR.com! Welcome to my detailed overview on 5.0 Resto’s four lug rear disc brake conversion kits fitting the 1979 to 1993 Fox Mustangs.
If you’re in the market to ditch the factory rear drum brakes, improve braking performance and retain your loyalty to a four lug setup; then a four lug rear disc brake conversion from five oh resto is for you.
There are three separate kits for three separate applications; 1979 to 1986 cars, 87 to 92 cars, and finally, 1993 cars. The majority of the components are the same throughout all of the kits. A few differences are master cylinders, parking brake cables and axle hard lines.
1979 to 1986 Foxes will include an SVO master cylinder and no axle hard lines. So, if you are converting a 79 to 86 car you will need to purchase or borrow a line flaring tool. This tool is needed to cut and properly flare the factory axle hard lines so that the included line fittings screw into the supplied brake hoses. Other than that modification, this kit is completely turn-key and includes all of the needed components to convert your 1979 to 86 Fox to four lug rear disc.
1987 to 1993 Fox Bodys are the exact same except for one small thing; parking brake cables. Without getting into the specifics, 87 to 92 owners will need an 87 to 92 kit; likewise with 93 owners, you’ll need a 93 specific kit to work with your car. Each kit will include a 1993 Cobra master cylinder and the needed three port to two port master cylinder to factory hardline adapter.
Now, 1987 to 1993 owners are in luck. Both of these kits include our SVE axle hard lines which are a direct bolt in. This means you do not have to cut and flare your factory lines. These SVE lines feature similar bends, so minimal bending is required whenever you do get them installed. They also feature the correct line fittings so they bolt directly to the included brake hoses and the factory center upper axle hose. Like the 79 to 86 kit, both the 87 to 92 and 93 kits are turn-key as well.
Each of these kits are going to include everything you need to make this four lug rear disc swap possible. Master cylinder, drive and passenger side calipers, caliper brackets, pads, rotors, hoses, proportioning valve, proportioning valve plug, parking brake cables, brake dust shields, and of course all of the needed attaching hardware.
Alright guys, follow along as I walk you through my process on converting this 92 coupe to four lug rear discs.
To begin installation, support the car via a lift or jack stands.
Remove both rear wheels.
Remove the sway bar if equipped.
Position a drain pan or bucket underneath the center section.
Loosen and remove all of the bolts except for the top one.
This will keep the cover in place while you pry it open to drain the fluid.
Now, go ahead and pry the cover free with a flat head or pry bar.
Allow the majority of the fluid to run out of the rear end and then remove the last bolt.
Set the differential cover aside for now.
Go ahead and scrap away any old RTV from the rear end to diff cover mating surface.
Spray quality brake clean into the rear end to thoroughly clean the carrier and the surrounding components.
Rotate the carrier so that the cross pin bolt is accessible.
Loosen the cross pin bolt and then slide the cross pin out of the carrier.
Now you can remove the drums from each side of the axles.
If the drum is stuck, lightly tap it with a hammer to free it from the backing plate.
Push in an axle and then remove a c-clip.
Use a rag to catch any fluid that may run out when you remove the axle from the housing.
Do the same for the other axle.
Mark the driveshaft with a paint pen and then remove the four driveshaft to flange bolts with a 12-point 12mm socket.
Remove the driveshaft from the car and then plug the tail shaft on the transmission.
Removing the driveshaft will allow clearance to remove the parking brake cables.
To do this, remove the loop brackets securing the parking brake cables to the lower torque box.
Remove the cable eyelets from the front parking brake cable.
Pass the cable through the guides and then depress the clips on the cable retainer with a box end wrench.
Finally, remove the cable eyelet from the drum brake assembly and remove the two cables from the car.
Now, use a combination of a deep socket and box end wrench securing the brake backing plate to the housing.
Use a line wrench to remove the brake hardline, from the back of the backing plate.
Remove the backing plate and then cap the hardline.
For the next step, removal of the lower shock hardware will help with additional clearance when fastening the brake line bracket.
Position the bracket over the shock mount on the axle housing.
Mark the bolt hole with a permanent marker.
Mark the area for the alignment tab or just simply cut the tab off with a cut off wheel.
Once you have made the needed marks, remove the bracket, spray some WD-40 over the marked areas for lubrication and begin drilling each hole with a quarter inch drill bit.
You may have to enlarge either of the holes to five sixteenths to get the tab or bolt hole aligned with the shock bracket.
Once the holes are drilled, clean the area with brake clean and then debur the holes.
Secure the brake hose bracket to the shock bracket with the supplied bolt.
Repeat those steps for the other side.
This kit includes the needed axle lines so you don’t have to cut and flare the factory lines.
I made life easy and removed the center upper axle hose for the next steps.
Remove the banjo bolt securing the hose to the upper hardline.
Remove the nut securing the upper axle hose bracket to the rear end housing.
Now, remove the upper axle hose and axle line assembly from the car.
Inspect the upper axle hose and replace if worn.
Install the supplied SVE axle hard lines into the crossover block on the upper axle hose.
The longer of the two lines will be for the passenger side.
The purple fittings will screw into the upper axle hose block and the red fittings will screw into the soft line you installed previously.
Loosely thread the lines into the upper axle hose.
Tighten the nut securing the upper axle hose bracket to the rear end housing.
Use two new crush washers to the secure the upper axle hose to the upper hardline.
Now, carefully bend the new hardlines so that they sit parallel with the axle tubes.
Also, you will have to carefully bend the lines so that the red fittings sit flush and even with the soft lines.
Once all bends are completed, tighten down all of the fittings with the appropriate line wrenches.
Double check all of your bends and make sure the lines do not come in contact with the upper control arms or read end housing.
Next, reuse your previously removed hardware that securing the brake drum backing plate to the housing.
Slide the bolts back through the housing with threads on the outside.
Position the supplied caliper brackets over the bolts.
They are marked “R” for passenger side, and “L” for drive side.
Tighten down the nuts using the same combination as before.
Next, install the dust shields with the supplied hardware.
These are not side specific, but should be positioned so that the caliper bolt holes on the caliper bracket are not covered.
Tighten down the hardware.
Now, take this time to inspect your axle bearing and seals.
Replace if worn.
Do the same for the other side.
Carefully slide the axles into the housing.
One at a time, push an axle in, install the c-clip and pull out to lock it into place.
Do the same for the other axle.
Reinstall the cross pin and retighten the cross pin bolt.
Reinstall the lower shock hardware.
Before reinstalling the diff cover, make sure the mating surface is completely clean and no signs of old sealer is present.
Clean your cover and reinstall it.
Be sure to either use the Lube-Locker gasket we carry at LMR.com or apply fresh RTV.
Torque the bolts to; 20 to 25 lb/ft working in a star pattern and starting with the bottom bolt.
Clean the front and backsides of the included rotors and slide them over the studs.
Use a lug nut to hold them in place while you install the calipers.
Position the caliper bracket over the rotor and use the supplied hardware to tighten it down.
One washer will be positioned under the head and the other between the caliper bracket and axle housing bracket.
This will help shim the bracket so that the rotor sits even in between the caliper bracket.
Place the supplied rattle clips onto the caliper bracket.
Be sure to apply a thin film of grease to the pad contact areas.
Install the pads.
Apply a thin film of grease onto any pad contact point on the brake caliper.
Position the caliper over the pads and tighten down the hardware.
Slide a crush washer over the banjo bolt.
Slide the banjo bolt through the brake hose block.
Place another crush washer over the bolt and then thread the bolt by hand into the caliper.
Tighten down the banjo bolt and be sure you properly crush the crush washers.
Do the same for the other side.
Now, find the end of the included parking brake cable that has the small groove in it.
This end will slide through the caliper and lock in place with the provided E-clip.
Slide the eyelet through the caliper mount and hook it into the parking brake clip on the caliper.
Push the cable sheath into the caliper mount and secure the cable with the provided E-clip.
Route the new cable in the same direction as the old cable.
Pass it through the opening underneath the car and push this end of the cable toward the center of the car until the clips lock into place.
Route the cable through the guides and then hook the other eyelet into the front parking brake cable.
Do the same for the other side.
Reinstall the cable to chassis retaining hooks.
Reinstall the driveshaft and tighten the bolts.
Unscrew the fill plug with a three eighths extension.
Fill the differential with two quarts of fresh gear oil and friction modifier.
Retighten the fill plug.
Reinstall the sway bar.
This will complete the rear portion of the install.
Moving to the engine bay, disconnect the low fluid level sensor on the master cylinder.
Position it out of the way and then remove the two nuts securing the master cylinder to the brake booster.
Before continuing to the next steps, place several old rags underneath the factory proportioning valve to catch any fluid that runs out.
Remove all three hard lines from the master cylinder.
Two on the side and one on the bottom.
Remove the master cylinder from the car.
Take this time to wipe up any brake fluid that may have come in contact with painted surfaces.
If you do not remove this within a timely manner, it will eat through the paint.
Remove the two hard lines from the factory proportioning valve.
Now, use an open end wrench to support the proportioning valve while you loosen the three quarters inch hex head plug.
Remove the plug and then gut the factory proportioning valve.
Transfer the o-ring on the factory plug to the supplied proportioning valve plug.
Thread the included plug into the proportioning valve and tighten it down.
Install the supplied master cylinder over the studs on the brake booster and tighten down the previously removed nuts.
Remove the port plugs and thread the supplied line adapters into the primary cylinder on the master cylinder.
This is the port closest to the firewall.
Thread the bottom factory line into the t-fitting.
Use the other supplied line and install it into the top port on the t-fitting and the back port on the factory proportioning valve.
Loosely tighten the fittings.
Transfer the factory hardline that was threaded into the front port on the factory master cylinder.
Thread this line into the first port on the factory proportioning valve.
Tighten this fitting.
Now, carefully bend the line so that the upper fitting sits flush with the port on the new master cylinder.
Thread and tighten down the fitting.
Reconnect the low fluid sensor.
Locate the union fitting on the passenger side.
Loosen and remove the two hard lines from the union and discard it.
Thread the supplied line adapters into the “In” and “Out” ports on the included proportioning valve.
The port marked “In” will go to the line coming from the firewall.
The port marked “Out” will go the line leading to the rear of the car.
Tighten down the fittings.
Thread the knob all the way “in” or clockwise to allow full pressure of the brake system.
Once the brakes are bled, a setting in-between fully tight and fully open will yield a proportionally adjusted line pressure.
Now it’s time to bleed the brakes.
Open the master cylinder cap and fill the reservoir with the appropriate brake fluid.
Fill until the fluid reaches the “max” line on the reservoir.
Close the cap and remove the front wheels.
Grab a bucket or bottle and a quarter inch inner diameter clear hose.
Position the hose over the bleeder starting on the passenger rear caliper.
Have someone inside of the car pump the brakes two or three times and hold.
Open the bleeder and then close it.
Repeat this until fluid starts to flow.
Move to the driver side rear and repeat the steps.
Then to the passenger front and finally to the driver side front caliper.
While doing this, make sure the master cylinder reservoir stays topped off and doesn’t run empty.
Since I installed new axle hard lines, a new master cylinder, and rear calipers; I would repeat the process one more time to ensure all of the air is out of the system.
Once complete, the pedal should be very firm.
Don’t forget to set the proportioning valve in-between fully closed and fully open.
Double check your work, and then take a light test drive.
Finally, enjoy the increased stopping power from five oh resto’s four lug rear disc setup.
Installation time will vary depending on the skill level of the individual. I personally would allot yourself an afternoon with a friend to help lend a hand. Other than the 79 to 86 owners having to cut and flare their factory hard lines, these kits are a direct bolt in. Keep a few things in mind before you install this kit; You will obviously need fresh gear oil and brake fluid, but consider replacing the center upper axle hose as they are often times worn and deteriorated. As well as new axle bearings and seals while you have the axles removed from the housing. All of those components can be purchased on our site, LMR.com.
If you’re in the market for a quality, rear disc setup; pickup one of these five oh resto rear four lug setups! Until next time, subscribe to our YouTube channel for content covering 1979 to 1993 Mustangs; and keep it right here with the real Fox Body enthusiasts, Late Model Restoration.