Yeah, I know, another disc question

I call upon my wise Jeeping brothers who...have traveled the path I am about to. Before asking, I have researched the internet, gone thru some 200+ pages of past posts on this website (learned alot) and still have questions. The D30 (73 Cj5) disc brake conversion. I received my Chevy Caliper mounts via UPS Tues. I will use the 77-78 Jeep rotors. The calipers, Chevy 1/2 or 3/4 ton calipers depending on caliper piston size difference, if any. One of my questions is what master cyclinder to use ? Direct fit is nice but, modification is O.K. if it is better. This will be non-power asist and maybe in the future, rear disc also. perhaps later Jeep or Chevy truck ? I thought that those who did the conversion might have encountered "surprises" or wish they would have done something differently. In advance, I thank you all for sharing your wisdom and experence.

 

I just did my conversion. I used the d30 off my 75 cj5 and used the knuckles and calipers off of a 77 cj7, bought new rotors for a 77. The stock MC from my 75 work just fine. I've herd that sometimes you have to replace the proportioning valve if it locks the fronts up b4 the rears, or overpower the fronts. But so far so good. You'll absolutly love it when you get disks on the front . When you have to get on the brakes you don't end up in the other lane and brake fade is nonexistant. I've read a lot about the chevy brake conversion, but I already had the other axel available.

 

I have done the chevy brake upgrade , I used the master cylinder off a 1977 - 78 Cj with the 6 bolt caliper brackets( they use the 1 1/8" rotors ) .
Proportioning valve I used off a 78 as well , have no problems everything works great .

 

I did exactly what CJ4U did with the same results. Later I added power brakes and switched to a master that matched my '77 booster. Oh, one problem. My hubs on my 74 were not machined on the surface wear the rotor goes, so I had to buy new hubs. Anyone want some old hubs?

 

I had no problems using an XJ/YJ MC and booster on mine. They are cheaper and more plentiful in case you can't find a CJ. Factory fit would be nice, though, if you find one.

 

i used a manual 82 jeep mc and an adjustable prop valve. The Mc was a direct fit on the firewall, but i did have to swap the push rod from the original to the new one (different length), if you do this be careful that the springs don't pop out. It works great.

 

I installed a dana 44 with disk brakes in the front of my 73 many years ago, I used the stock master cylinder, but I removed the check valve for the front brakes on the master cylinder. You just remove the front brake line of your master cylinder, pull out the check valve. You might have to use a sheet metal screw and pull on it with some visegrips. Drum brakes require a small amount of pressure to be left in the brake line to keep a high pedal because drum brakes have return springs returning the shoes to the wheel cylinder and disk brakes return on their own. My brakes worked well, you will love the disk, Oh, the front axle brake line on my jeep was at the rear of the master cylinder, make sure you double check!

 

I did the same thing first, but the brakes were favoring the rear too much and the rear brakes ended up doing most of the stoping power.

 

That's why you use a proportioning valve.

 

Thanks for sharing your knowage and experience. You all have helped me decide what to get to jump into this. I flipped my Jeep end over end 10yrs back because I had to swerve instead of brake to avoid becoming one with a bus bumper. Since then I started driving my jeep with more forsight. Disc's will be great !

 

I converted my 73 D30 to disk with parts from a 78 D30. I used the knuckles, spindles, calipers and brackets, and hubs. IIRC the hubs on the 78 and 73 were the same but I used the 78 to keep it all the same.

As for the MC I am using the stock 71 unit. I checked to see if it had any internal residual valves, which it did not, and then installed a 2lb Wilwood unit to the front and a 10lb valve to the rear 11" drums. I have no problems and the brake feel is good.