Brake question for '72 Cj5.

Alrighty yall, ran into a snag today. I started to adapt the brake lines from the original CJ hard lines to the toyota lines on the axle. Problem is, the fittings are different which aint a problem since Im just going to have fittings made to adapt the two together. I did read though that since I am switching to disc in the front, that I need a master cylinder that has 2 front output lines and a valve to put more preasure in the front then the back and equal preasure to each front wheel. Any suggestiongs would be great. I can get a Cj7 master cylinder for around 20 from the auto part store but not sure about the valve. Thanks again.

 

So it sounds like you are using a Toyota front axle. What are you using in the rear? Disc in rear? Drum in rear? Helps if you fill in all pertinent info


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Im running a toyota 8" front axle out of an '85 toyota pickup with the stock disc setup and a rear 8" from a '92 toyota 4runner with stock drum setup.

 

Right on, thanks a lot. Now about the proportioning valve, do I NEED to run one? From what I have gathered thus far, its just a valve that allows the rear drums to start applying first and then the front discs but allows more preasure to the front then the back and equally. Is the info accurate?

 

Proportioning valve controls the amount of pressure going to the rear brakes to help keep them from locking up before the front start applying. So yes, you need to run one in most applications. Adjustable units are readily available from Summit Racing, Jeg's, Speedway Motors, and lots of other sources and are fairly inexpensive.


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Jeep started using a proportioning valve in the CJ models in 1973 or 1974. You can read about the '74 combination valve (proportioning valve plus differential warning switch) here http://oljeep.com/gw/74_tsm/9-BrakesWheels.pdf but the '76 description is better http://oljeep.com/gw/76_tsm/Section9.pdf

You don't have to have it, since a '72 model did not have one. Jeep did feel it was enough of an upgrade that they included it in later models. Note that the disk brake Wagoneer valve had an additional metering section.

 

Thank you both very much for the response. I will look into the links you provided me timgr. The jeep will be a mainly off road vehicle but it will also be a weekend cruiser and around town rig as well...no trips longer then 30 minutes due to speed. I figure without a valve, then the brakes would work just like the originals where if you had to mash the pedal then all 4 tires would be given roughly the same amount of preasure? Also, which master cylinder would you guys recommend?

 

I'd run a proportioning valve especially for an off road vehicle. Picture yourself climbing a steep hill, having to back down, hit the brakes to control the decent, and the rear brakes lock up. Not a pleasant situation nor is it safe. That's why vehicles became equipped with them. Some vehicles (primarily earlier but some later) compensate for this with specific wheel cylinder diameters. Much easier to install an adjustable unit so you can dial it in for your set up and needs.


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One more thing that I found out the hard way. There should be a residual pressure valves in the brake cylinder. For drum brakes it's like ten lbs. For disc's it's like 2-1/2 lbs.. From what I read this pressure keeps the brake shoes closer to the drum so the shoes travel less.. Otherwise you are pumping brakes. If used on a disc setup the pads will drag.. At least thats what I found out when having brake issues after installing a Corvette master cylinder..

 

Alrighty thank you guys. I was talking to my brothe in law earlier today and he was saying that I could use a valve off of a mid 70's chevy truck (or any year that does not have ABS) and that it would work. Or should I stay with AMC and look for one off a cj or waggy?

 

I know I can buy one from an auto part store but Im trying to keep the cost down for now since I will be converting to power brakes with a complete kit later on once my jeep fund is built back up. I just have to get it movable.

 

Here is the proportioning valve I am using: http://www.amazon.com/Wilwood-260-8...7IEA/ref=sr_1_1?ie=UTF8&qid=1336625264&sr=8-1 with free shipping it was cheaper than Summit.

 

That will work now and with future upgrades.

Just an FYI, a residual pressure valve DOES NOT keep the shoes closer to the drums. That's what the adjuster is for. It does keep pressure on the system to hold the wheel cylinder cup seal lips tight against the inside of the bore so pressure does not bleed down. Systems where the wheel cylinders have cup expanders typically do not use residual pressure valves. In a system where the m/c is mounted low, like on the frame, it keeps the fluid from draining back to the m/c.


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Thank you both again for the replys. Like i said before, I have a fair share of upgrade knowledge however, brakes was never part of it. So im leaning towards ordering that valve that renegade showed me and then buying a remaned m/c from auto zone from a 78 cj7. sound like she would work?

 

First off, thank you all for the replys and for the help. After some studying, I decided to go with a brake setup off of a jeep yj. I can get the mc, booster and prop valve shipped to my door for right around 50 bucks (used of course). Figured for the price, might as well convert to power while im at it now. Again, thank you all.

 

Ok so i was doing some thinking and was swirling the thought around in my head about trying to use a toyota 4x4 master/booster/valve since im running...toyota axles...makes scense to me. I know i can put on the yj setup with very little mods...but was wondering what you guys think about the toyota one. Here is a picture of the two units:

This is a unit for a wrangler YJ



And here is a unit off of a 4runner 4x4 89-92.


the toyota unit is shorter and has the valve already mounted to the unit...so the brake line portion would be a LOT easier to deal with but like stated before, i aint no expert by any means and want your guys opinion. Thanks.

 

gonna have to bump this back to the front, sorry guys but if anyone has any input on the two masters, i would really appreciate it. Going to try to order me a unit in the next week or so and would really like to run the toyota unit to match my axles but not sure. Any input would be great. Thanks.

 

The Toyota setup makes more sense as then all the parts are matched. However, check the diameter and make sure you have enough room under the hood/cowl area. It looks to be a larger diameter from the pics.

 

Ok thanks for the advise...never even thought about that. As for the brake light and mounting...it looks like the toyota has a plug style connection so im assuming i would have to figure out which wires i need to connect my original brake wires to? And for the mounting of the unit, if the holes dont match up then maybe make a plate with the toyota holes, mount that to firewall then mount the unit? Sorry for asking so many questions but my searchs have came up with nothing about this and im not too fimiliar with brake systems...im learning.