Rear Drum to Disc Conversion

[1973stang]

I am upgrading the handling of the car based on answers to my previous thread.  All parts are ordered and work will begin end of the month.

THOUGHT to convert Drum to Disc for the rear.  I researched the forum and there are different setups being discussed and got a bit confusing...so I thought to ask specifics.

I HAVE POWER BRAKES.  Disc in front and Drum in rear.

1) Which kit would you reco for this job?

2) Do I need to change the booster to handle disc in the rear?

3) Do I need to add proportional valve also??

Any other things to consider.

Rush

 

[turtle5353]

One way you can go, that a lot of people over look, is to replace the whole rearend. If your rear end doesn't have posi or the gears you want, you can swap in an 8.8" rear end out of a Ford Explorer. I swapped one in my car years ago and its been holding up really well. You get factory disc brakes, 3.73 gears, factory posi, and 31 spline axles all in one shot. Just another idea for ya. You can do a search on here, its been discussed a few times.

 

[Jeff73Mach1]

there is a set of brackets made and sold by "Mustang Steve" that utilize 2004 Cobra brakes- works well, nicely made. I 1st used Baer Brakes, but their brackets are cast aluminum and I had one fail and destroy a wheel. When I called them aabout a replacement caliper, they would not even admit that their calipers are just 2004 Cobra calipers, nor would they tell me that these calipers use slightly thinner pads than the Mustang calipers.

You'll want an adjustable rear proportioning valve to dial in the amount of braking pressure and you may benefit from getting a gauge to test line pressure to make sure you are in the proper ballpark as disc brakes take something like 900-1500 psi line pressure and drums are like 600. Needing a different master cylinder is a distinct possibility.

Most of the conversions won't fit stock or aftermarket 15" wheels, so if you are not upgrading wheels, don't upgrade the rear drums.

Drum brakes aren't bad-there are a couple of cheap tools that make servicing them easier than trying to manage with pliers and a big screwdriver. They work fine even for spirited driving, but they will fade to some degree-I think people overestimate the value of rear disc brakes as the front of the car does the lion's share of work. It can be done for about $500.00 but even having done it, I'm not sure it is worth it.

 

[Don C]

Your existing booster is fine. Most people do not replace the existing (factory) proportioning valve or master cylinder. Rear disc brakes also require lower operating pressures to prevent them from locking up. An adjustable proportioning valve will enable you to fine tune the front/rear bias. The smaller reservoir for the rear brakes will require you to keep an eye on the brake fluid level as the rear pads wear and the pistons do not return as far. Self adjusting drum brakes keep the fluid level at the same level as the shoes wear, which is the reason for the smaller reservoir.

Mustang 360 has a couple of articles:

http://www.mustangandfords.com/search/?q=disc%20brake%20conversion

 

[Mister 4x4]

There's also an article floating around the forums outlining swapping in some Crown Victoria rear discs onto the stock 9" axle (just gotta buzz the bottom of the axle tube flanges flat to accommodate - from there it's pretty much a bolt-on deal) - which I believe are very similar in size to the Explorer discs Kevin mentioned with his Explorer rear-end swap (which is a great idea, BTW).

Lots of different ways to skin this cat.

 

[turtle5353]

There's also an article floating around the forums outlining swapping in some Crown Victoria rear discs onto the stock 9" axle (just gotta buzz the bottom of the axle tube flanges flat to accommodate - from there it's pretty much a bolt-on deal) - which I believe are very similar in size to the Explorer discs Kevin mentioned with his Explorer rear-end swap (which is a great idea, BTW).

Lots of different ways to skin this cat.

The Lincoln Versailes used a disc brake 9 " also.  I had one in my Bronco II.

 

[Don C]

Bolt on using stock components is the best way to go, in my opinion. That makes it easy to find replacement parts, not to mention cheaper for cheapskates like me. Replacement parts for specialty items can be hard and expensive to obtain.

Here are a couple of websites with instructions:

http://www.boyerfour.com/mustang/rear/small_bearing_ford_8_9.htm

http://ynned.tripod.com/crown_vic_discs/index.html

http://www.jalopyjournal.com/forum/threads/disc-swap-to-ford-small-bearing-9-or-8-rear-ends.358587/

These may not work with 14-inch wheels and may require upgrading to 15-inch or larger.

 

[Mister 4x4]

I was thinking of you when I mentioned using the Crown Vic parts.

 

[Stanglover]

One thing I DON'T want to do is wreck my original numbers matching open dif 3.25 rear axle. I would however like to consider adding a 9" 3.50 locker type rear axle and disc brakes would be a bonus. I am not hijacking this thread, but do any of you know of such a rear end that is easily available and be a direct fit in the Mach 1 with staggered shocks and at present 14" wheels? This might be a good way for 1973stang the  to go also.

 

[Don C]

I was thinking of you when I mentioned using the Crown Vic parts.

:goodone:

 

[Jeff73Mach1]

Humbly, I assert that if you care about keeping your original rear end, you probably shouldn't waste the energy on doing a disc brake conversion-nothing worthwhile will fit within the 14" wheels. If you find one that advertises fit, ask them to send you a template to check your wheels for clearance

If you want to keep it original, keep it original.

Housing ends can be replaced if you alter them, not a big deal at all to have new ends welded on.

 

[Jeff73Mach1]

Sorry, double post

 

[Mister 4x4]

One thing I DON'T want to do is wreck my original numbers matching open dif 3.25 rear axle. I would however like to consider adding a 9" 3.50 locker type rear axle and disc brakes would be a bonus. I am not hijacking this thread, but do any of you know of such a rear end that is easily available and be a direct fit in the Mach 1 with staggered shocks and at present 14" wheels? This might be a good way for 1973stang the  to go also.

I think you're asking for too much in one package.

You're better off putting your original axle aside and getting a new 9" - build it with the 3.50 locker diff, then add the disc brakes (if you can find them for 14" wheels - as has been mentioned).  An axle is an axle, so staggered shocks are not a problem (they mount to the spring pads - not the axle itself).  The Ford 9" diffs are the easiest to swap ever - everything involved with the differential (ring & pinion, locker, carrier, yoke, etc.) is part of the 'drop-out' unit - pull the axles out of the ends of the tubes a few inches, then unbolt the diff and swap it... easy-peasy.  As for the disc brakes - good luck finding any to stuff into 14" wheels.  There might be some GM stuff out there somewhere, but I don't believe there are many, if at all, Ford units to fit 14" wheels.

 

[Bentworker]

1)Street or Track http://www.streetortrack.com/Street-or-Track-11.65-Rear-Disk-Brake-Kit-pr-23990.html (I have never seen them in person, but if I was to do mine again this is what I would choose)

2)Stock booster is fine.

3)You will need a proportioning valve. I’m partial to the Wilwood ones.

You may have to use a different size master cylinder depending on what the kit manufacturer recommends

I have the Mustang Steve rear brakes on my car. There are a couple things I don’t like about them. The parking brake isn’t great, and there isn’t an off the shelf cable that works for it. In my case there was a bit of a tolerance issue on the bracket that was supplied, and I had too much endplay (had to shim the bearings). The street or track kit uses a drum in hat parking brake system that seems better.

Peter

 

[Stanglover]

One thing I DON'T want to do is wreck my original numbers matching open dif 3.25 rear axle. I would however like to consider adding a 9" 3.50 locker type rear axle and disc brakes would be a bonus. I am not hijacking this thread, but do any of you know of such a rear end that is easily available and be a direct fit in the Mach 1 with staggered shocks and at present 14" wheels? This might be a good way for 1973stang the  to go also.

I think you're asking for too much in one package.

You're better off putting your original axle aside and getting a new 9" - build it with the 3.50 locker diff, then add the disc brakes (if you can find them for 14" wheels - as has been mentioned).  An axle is an axle, so staggered shocks are not a problem (they mount to the spring pads - not the axle itself).  The Ford 9" diffs are the easiest to swap ever - everything involved with the differential (ring & pinion, locker, carrier, yoke, etc.) is part of the 'drop-out' unit - pull the axles out of the ends of the tubes a few inches, then unbolt the diff and swap it... easy-peasy.  As for the disc brakes - good luck finding any to stuff into 14" wheels.  There might be some GM stuff out there somewhere, but I don't believe there are many, if at all, Ford units to fit 14" wheels.

 Thanks. I guess I was basically thinking out loud. IF I ever did swap the rear axle, of course the original would be stored with all the rest of the stuff that has been "temporarily" removed. Nothing of any consequence gets chucked if it means originality. As for keeping the 14's, I'm open to switching to 15's as I need new tires anyway. I never did have the original steel 14" rims.

Thanks for your suggestions and good info as well for the original poster.