REAR DISK BRAKES
INTRODUCTION
This article entails the process I went through to install rear disk brakes on my 89 4Runner. The reasoning for doing this was to eliminate mud buildup in the rear drums and to reduce the expense of maintaining the rear brakes due to the cheaper cost of the Chev rotors and calipers compared to the Toyota drums. Also my e-brake has not worked for a while and I got tired of adjusting the rear brakes all of the time. The reason I went with the Monte-Carlo calipers instead of a caliper that has the e-brake built on to it is that I am going to install a drive shaft e-brake instead as the caliper e-brakes are not supposed to work very well.
PARTS NEEDED
2 X 78-88 Front Monte-Carlo Calipers
2 X Front Brake Pads For Above Calipers
2 X Caliper Pins For Above Calipers
2 X Flex Hoses For Above Calipers
2 X Special Bolt For Above Flex Hoses
2 X 86-89 Front Chevy Light 4X4 Vented Rotors 1" Thick
2 X Wheel Bearing And Inner/Outer Seals For Rear Toyota Axle
1 X Wilwood Proportioning Valve
1 X 90-93 1" Bore Master Cylinder for V6 non ABS Toyota Truck or 4Runner
3/8" x 4" x 20" Piece Of Sheet Steel.
Misc. Brake Line And Metric and SAE fittings
Here is a pic of some of the
parts.
DISASSEMBLY
Start by putting the vehicle on axle stands and removing the wheels. Then drain the differential using a 15/16" Socket. Next remove the drums, shoes, and springs from the drum backing plate. Then Disconnect the emergency brake cable from the backing plate. Then remove the four 14mm bolts from the back of the backing plate where it bolts to the axle tube. Next slide out the axle assembly and set aside. Repeat for both sides.
Here is the stock axle being
drained.
Here is the backing plate minus
the drum/shoes/springs.
Here is the axle assembly after
removal.
Here is the side of the axle
tube containing the inner seal.
MACHINE SHOP WORK
Now you have to take the axle assembly to the machine shop or garage and get them to press the axles and bearings out. Get them to discard the backing plates and put everything back together with the new bearings and outer seal installed. You also have to take the rotors in to a machine shop and have them enlarge the center to 4.125" to clear the larger Toyota center hub.
Here is a scan of the axle
assembly from the Hayes manual.
Here is a pic of the rotor back
from being machined.
PRE-ASSEMBLY
Now that you have everything back from the machine shop you can put the axles back in the axle tube. Start by installing new inner seals. (I use a claw hammer to remove the old one, then clean the surface and install the new one by gently tapping it into the axle tube with a hammer and a round block of aluminum that fits completely over the seal) Next you can slide the axle into the tube so that it slips into the 3rd member and the studs slide into the four holes in the axle tube.
MAKING THE BRACKETS
This is definately the most time consuming of the whole proccess and if you don't have access to a drill press and chop saw or band saw then you might be better off taking my plans into a machine shop and getting them to make the brackets for you.
The way I did this was just to cut out the patterns from my plans and scribe them onto the sheet of steel. The only part that is critical is the position of the holes that bolt to the axle. After I had the design traced onto the steel I drilled out the holes with a drill press. The holes that go over the axle studs have to be just big enough to fit and the holes for the caliper pins have to be drilled out with a 3/8" bit and then tapped to a 7/16" SAE thread as the caliper pins screw into these holes. It is very very important that you make sure the tap goes in straight or it will be harder to get the caliper bolted on after everything is done.
Next I used a chop saw (for the straight cuts) and a jig saw (for the curved cuts) to cut the brackets out of the steel, then I used an air grinder to smooth the edges. Next bolt the two axle brackets onto the axle studs and the two caliper brackets to the caliper using the caliper pins and having the pads installed in the caliper. Next slide the caliper onto the rotor and position it in the proper position using a clamp so it doesn't move. Then using a pair of vice-grips clamp the inner and outer brackets to each other to make the whole thing rigid. Make sure the rotor, caliper and pads are not touching where they shouldn't be touching and if everything is proper then spot weld the brackets to each other just to hold them together. Then remove the vice-grips and the caliper from the brackets, remove the brackets from the axle tube and then weld the brackets properly making sure to get good strong welds with a lot of penetration. I then used the air grinder to smooth out the welds and then painted the brackets with Tremclad. You may also be required to grind down the inner edge of the top bracket to get the caliper not to touch. (you will know what I mean when you get to the point of test fitting everything to find out where to weld them together) Repeat for other side.
This is a pic of the outside of
the completed setup.
This is a pic of the inside of
the completed setup.
This is the plan I made for the
brackets. (make sure you print it out at 150dpi so that it will be true
size)
Now that you have the brackets made you can put it all together. Just bolt the brackets onto the axle tube and then bolt the calipers and pads to the brackets.
RUNNING THE REAR BRAKE LINES
Next what I did was to remove all of the old emergency brake cables, brake lines going from the tee on the axle to the old wheel cylinders and the proportioning valve. The proportioning valve has three lines going into it. Take the one that comes from the master cylinder designated for the rear brakes and attach it right to the flex hose that goes to the rear axle. Then take the one that goes to the front brakes and remove it entirely plugging the tee at the front that it was attached to with a plug. (All I did was take a old metric fitting and weld the hole in the end of it to make it a plug) Doing this separates the rear brakes from the front and eliminated two extra lines. Then I attached the flex hoses to the calipers and made the brake lines that go from the tee on the axle to the flex lines. To do this I purchased pre-made line with the SAE fittings installed. I then cut off one of the SAE fittings and installed one of the metric ones off of the old lines using a flair tool.
Here is a pic of the axle
underneath after completion
Here is the old prop valve removed.
Here is the tee after it was blocked.
RUNNING THE FRONT BRAKE LINES
Moving to the front we now have to install the new master cylinder and proportioning valve. First remove the old master cylinder. Next I cut the metric fitting off of the line that goes to the rear brakes and installed and SAE fitting using the flair tool. Then I made a short line to go to the master cylinder with an SAE fitting on one end and a metric on the other. Then I attached the line that goes to the rear brakes and the short line that goes to the master cylinder to the proportioning valve. Next I bench bled the new master cylinder and bolted it to the booster. Then I re-attached the brake lines to the new master cylinder.
Here is a pic of the master
cylinder
Here is a pic of the
willwood prop valve
FINAL STEP
Now all that remains to be done is to bleed the brakes and fill the differential back up with gear oil. The only thing to remember is to start at the rear drivers side caliper and get an assistant to pump the brakes with the bleed screw loosened. One you don't see anymore air in the fluid get your assistant to hold the pedal to the floor and then tighten the bleed screw. Next do the same process for the passenger rear then passenger front then drivers front calipers. You can then also bleed the master cylinder by getting your assistant to put the pedal to the floor and then loosen the brake fittings letting out any air and fluid. Then tighten the fitting back up. During this part make sure your assistant ALWAYS has the pedal to the floor before tightening the fittings and you never let the reservoir run low on brake fluid.
Now you should have lots of pedal pressure and it is time to put the tires back on and go for a drive. Find a local dirt road and when applying the brakes watch to see if the back locks up first. Make sure you don't go to fast initially because you will end up in the ditch if you don't have the brakes adjusted right. Depending on if front or rear locks up first adjust the proportioning valve accordingly. This is why I put my valve under the hood. I would hate crawling under the truck to adjust the valve. Repeat trying out the brakes and adjusting until all four tires lock up at the same time and you are done.
At the time of writing this article I had ordered but not received my residual valve yet. Some people have installed these just before the flex hose on the back axle and it is supposed to help for pedal travel. With the above master cylinder installed and the pads new it doesn't seem to be needed at all but as the pads wear and it takes more volume to get them to hit the rotor I can see the need for one. All the valve does is keep pressure on the rear brakes so that the pads don't move too far away from the rotors resulting in long pedal travel. I should be getting mine soon and I will post the results here. Click on the title heading to see WilWood's web page.
OVERALL IMPRESSIONS
After it is all said and done the new brakes work EXCELLENT!!!! The main reason that I did this was to eliminate the accumulation of mud and silt in the drums while reducing the cost of maintaining the brakes in the first place. With the 4 wheel disk brakes there is no longer a need to adjust the rear brakes anymore and it stops a lot better that before. (probably due the the larger master cylinder more than the brakes) After going off-roading there was no problem with mud in the rear brakes and I was able to control my decent down steep hills better. (especially backwards when before just the front wheel would lock up resulting in me just sliding down the hill).
If anybody has any comments or questions about the above article please feel free to e-mail me at