Overview

Yes, those Oh-my-God drum brakes on Generation 1 Toronados can be converted to either 2 or 4-wheel disk brakes!  You’ll have to do some scavenging in the graveyard, order some readily-available parts and a few special ones, invest some late-night work in the laboratory…and, oh yes, bring your wallet.

This document covers both 2 and 4-wheel conversions. In a nutshell, you can:

• add front disks to a '66-69 4-wheel-drum system
• modernize a '67-68 with the early-style optional front disks
• give any '66-70 Toronado 4-wheel disk brakes

What you’ll leave behind: long stopping distances, rear-wheel lockup, brakes that pull to one side if mis-adjusted, irritable self-adjusters, and a pile of steel parts for the recycler.

What you’ll gain: A 4500 pound, 385 horsepower car that’s not only fun to drive fast, but can stop!  The Toronado will never stop like a truly modern car but, wow, the disks stop soooooo much better than the drums.

Before going any further, many, many thanks are due to Phil Brandt for the original write-up on which this is based. I’ve borrowed liberally from his detail/description and augmented with some intro notes and comments here and there. Any errors or omissions are my fault. Not included in this description is Phil’s procedure for putting the TruTrack anti-lock brake system optional on early-mid 70s Toros onto the Gen 1 rear end. The TruTrack system is hard to find and entails substantially more work, since it was on a round axle and adapting it to the early-style beam axle requires careful cutting and welding.

And, a big thank you to the various people who have helped improve these guidelines over the last few years.

As stated above, you can convert 1966-69 Toronados with 4-wheel drums to 2 or 4-wheel discs.

You also can modernize the front brakes on a 1967-68 Toro (or a Cadillac Eldorado of the same years) with front discs and rear drums.  There are several reasons for doing this. First, '67 and '68 disc systems use expensive (and trouble-prone) 4-piston non-floating calipers. They also have unique rotors that combine the rotor and hub in one piece--replacements seem to be completely and utterly unavailable. Finally, the '67-68 spindles still use the expensive early-style wheel bearing that costs several times as much as the '69-forward bearing.

Converting the front brakes will make the biggest difference, but it is not much more difficult to do the rear ones as well. It isn't really necessary to do this, but you will gain a slightly better and simpler brake system all around, and a pedal with less travel. Plus, it's pretty cool to see disks on all four corners.  You will notice that the 4W disks also require slightly more pedal effort than a disk-drum system. Part of that is the nature of the beast, and part of it is the pads, too.  Semi-metallic ones, at least until they warm up, usually take more effort than organic ones.  In my opinion that's a very small price to pay. The 4W disks feel great when you use them, and the front and rear use the same rotors and pads.
 
 

Parts to convert or modernize the front brakes

For a straight bolt-in conversion for the front brakes, use the front hub/disk brake assemblies (with steering knuckles) from a ‘69-70 Toronado, along with the distribution block, master cylinder, power brake booster, metering valve and proportioning valve (either the factory one or an adjustable one—an adjustable one is preferable so you can get the front-rear balance just right for your car). It also is possible to use these parts from a ‘71-72 Toronado or Eldorado (and perhaps later ones, I just don’t know), except this conversion will also require ‘71-72 balljoints and tie rod ends. 

See note 7 below about simplifying the plumbing rather than using the OEM hodge-podge.
 

Parts to convert the rear brakes as well

For a mostly bolt-in conversion, use ‘76-78 Eldorado rear calipers, backing plates, emergency brake actuator levers, hubs, master cylinder and distribution block (and its bracket). The Eldorado rear rotors are the same as the ‘69-78 Toro/Eldo front rotors.
   

Additional Notes
 

1.  Wheels and clearance.  For a 2 or 4-wheel conversion, you will also need disk brake wheels, since the drum ones won’t clear the calipers. You can use the wheels from any ‘67-78 Toronado or Eldorado with disk brakes. You will need to verify the clearance between the wheels and the calipers and dust/gravel shields. You may find that the valve stem and/or wheel balancing weights rub slightly in certain places, and will have to fine-tune accordingly with placement, sandpaper, or a Dremel grinder.
 

2.  Brake booster.  If you are converting the brakes on a '66, you will need the later-style (1967 forward) larger diameter power brake booster, since the smaller '66 one doesn't fit the dual master cylinder.  
  

3.  Brake pressure warning switch.   Either conversion will mean using a distribution block which has a brake pressure warning switch built in. This can be wired into the parking brake dashboard light to give an additional safety improvement over the ’66 system.  It operates on a pressure differential switch--if the line pressure in either the front or the rear system drops, higher pressure in the other half forces the switch over to make an electrical connection to light up the bulb. You must follow the brake bleeding directions in the shop manual so that you get the brake failure light switch to center properly so that it will work in the future.
 

4.  Control arm bushing bolts.  If in this process you decide to replace the control arm bushings, be aware that the Grade 8 bolts for the control arms may have to be replaced. Mine were frozen and had to be cut out.
 

5. Axles stuck in hubs.  Also be aware that swapping the front brakes requires removing the spindles/hubs from the driveaxles. One of my axles was frozen solid in the hub. The only way to remove it was to cut the axle in half, then torch the hub to get the remnant out. Ruined the hub and the axle, but that didn't matter in my case since I was swapping in new axles along with the disk brake spindles/hubs. However, if you're considering using your existing axles, be ready for this potential problem.
 

6.  Axle replacement, flange bolts, centering rings, and flange vent holes.  If in this process you decide to replace the original driveaxles on a ‘66, be aware that installing replacement axles will require longer flange bolts (Grade 8), as well as Dick Taschenberg's centering rings for the output flanges.  However, when you replace 66 axles with the later version, be aware that they changed (slightly) the dimensions of the inner flange which bolts to the output shafts. So, there are three things you need to do.

First, you need to get a set of the later-style axle flange bolts. Since the newer flange is slightly thicker, these bolts are slightly longer. Yes, the 66 ones will fit, but they won't thread fully into the output shaft flange. These are high-grade bolts with fine threads and a small head, and sold as a set for any 67-78 Toro/Eldo. GM PN 394777

Second, the 67-forward axles have a slightly smaller diameter "cup" --that metal pressed-in cap on the inside of the inner flange that fits inside the transmission output shaft flange. So, the newer one won't seat tightly. It's real obvious, too, by measuring the diameter of the new cup versus that of the output shaft flange, or by just holding it up to it to feel the slack. God only knows why they didn't stick with the original dimensions. The solution is to get a pair of Dick Taschenberg's centering rings, which are spacer rings to fill the gap. GM used to make these but that was a long time ago. They stopped because it was only a problem for the 66 and very early 67. Don't put in later axles without the adapter rings .

Third, (and this is something that Dick's instruction sheet mentions), if your transmission output shaft flanges do not have a little vent hole drilled in them, you need to drill a small one (say 1/8" diameter max) to relieve air pressure in the inner CV joint when the axle moves back and forth, like in turns or as the suspension moves up and down. If you don't provide a hole in the output shaft flange, then the only relief available is for the pressure to push past the axle boot, which will squeeze grease out of the inner joint. Also, if you look at the end of the new axle you should see that the pressed-in cup I mentioned above has a small hole in it. If the pressed-in cup does not have a hole, then pierce it with a nail. It should already have one, though.

HOW TO CONVERT TO FRONT DISKS
(with adjustable proportioning valve)
 

1. Remove original drum/hub/knuckle assemblies.

2. As needed, install new suspension components per manual, drilling out original riveted balljoints on the disk brake knuckles. Do not torque control arm bushings or balljoints until car is lowered onto wheels and at proper ride height.

3. As needed, install new bearings and seals in the disk brake hubs.

4. Install knuckles, rotors, calipers and hoses.

5. Mount new distribution block in suitable location.

6. Bench-bleed and install new master cylinder and booster.  You will probably find it necessary to put a slight dimple in the inner wheel well to clear the new master cylinder/booster combo.  For 2W disk conversions, be sure you install the metering valve which ensures that braking begins with the rear wheels first (due to the greater fluid movement need with drum brakes to move the shoes against the drums).  Don't skip the bench-bleed--the Toro's master cylinder angles slightly upward when mounted, and you want to be sure there's no air trapped in it. Do be sure you do a thorough bleed job all around. If you're using a '66 shop manual, follow the master cylinder installation procedure on p. 5-10 and the bleeding on p. 5-6, following the right order of wheels.  Have someone there to help you! Don't worry about the tool mentioned in item 3 on p. 5-6.  You can do that by jury-rigging something, and it's not essential anyway.

7. Bend and install brake lines to distribution block and to hoses.

8. Install adjustable proportioning valve between distribution block and rear brakes and bleed the system. Placing it under the master cylinder is a convenient place.

9. Lower car and verify/adjust ride height. 1966 specs for torsion bar adjustment: ride height at 2 inches rear of the front door edge should be 8 inches from rocker panel to ground.

10. Torque control arms and balljoints to specifications.

11.  Re-check, verify, test everything before taking the car on the road. You've done a major modification to your car and must be sure that the brakes are safe.

12. Re-align front end. I have found that the following settings are within the ’66 specifications and work okay.

NOTE: For the 4-wheel conversion, if you use the Eldorado distribution block (technically called a combination valve since it has an integral proportioning valve), and if you are going to install an adjustable proportioning valve in-line to the rear brakes, you will need to remove the proportioning valve from the distribution block (accessible via the screw-in plug on the bottom) and replace the plug with a solid one.
 

1. Remove the Toronado drum brake/backing plate assemblies.

2. In each rear Eldorado caliper, the piston and emergency brake actuator and lever should be switched so that the brake lever actuates from above, not below. The Right piston/actuator/lever should be placed in the Left caliper, and the Left piston/actuator/lever in the Right caliper. Each actuating lever should be placed in roughly the 12 o’clock position. (Necessary because the design of the early beam axle precludes using the Cadillac brake lever position of 6 o’clock.)

3. Each backing plate has two identical "ears" with mounting holes for the emergency brake cable. Remove with a torch the ear that will be in the lower position when each backing plate is installed. Make sure that the backing plates clear the beam axle edges. Torch/grind as necessary.

4. Install backing plates with new Grade 8 fine thread bolts and nuts. Position the backing plate so that the slotted dust shield faces away from the caliper toward the middle of the car. The brake caliper brackets should be positioned so the caliper is to the rear of the axle, not forward.

5. Install the calipers to the backing plates and check fit. Some torching/grinding on the backing plates may be necessary to clear the brass brake line input elbow on each caliper.

6. Install rear hubs and rotors.

NOTE: The wheel bearings in the Eldorado hubs may or may not fit the early Toronado spindles. There are two possible solutions:

1. Verify fit and use the Toro bearings in the Eldo hubs
2. Use the Toro hubs. You will need to turn 3/8 of an inch off the hub diameter so the brake disks will fit. Have the turning done at a high-quality machine shop, since it must be perfectly centered and you don’t want to turn off any more than necessary!

8. Verify clearance with rear shock absorbers. It will be necessary to modify the rear shock mount ears on each leaf spring bracket to clear the calipers. Each ear should be cut off, moved approximately ½ inch inward and 1 inch rearward, then re-weld.

9. Bend and connect brake lines to the calipers.

10. Connect and adjust the emergency brake cable with some sweating and swearing. The original Toronado cable can be used, with some bracket work and after-market brake cable shorteners as needed. The brake actuating levers should be positioned on their shafts as far toward the rear as possible to activate the brakes securely.  Re-configure the location of the springs that actuate the emergency brake. You will hook them to the holes in the actuating levers and will need to hook the other ends to a point rear of the levers. The original holes in the calipers won't work because the springs will pop off when you use the emergency brake. Your new location for the springs must enable the actuating levers to fully retract when the emergency brake is released, or you will burn the brake pads.

11. Bleed and test the system, adjusting the rear proportioning valve as needed to the point where rear brake lock-up is just avoided.

12. Wire in the pressure warning switch in the distribution block so pressure failure will light up the brake warning light on the dash.

13. Re-check, verify, test everything before taking the car on the road. You've done a major modification to your car and must be sure that the brakes are safe.

14. Enjoy!