kook911 Posted January 31 Share Posted January 31 I have read most of the write ups on how eliminate the LSV. My question is on the proportioning valve does it matter if it is a XJ or YJ valve? I’m asking because when I search just for the YJ valve the options that come up show that the YJ and XJ valve are the same. So before I get into this I just want to make sure. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 31 Share Posted January 31 So long as you get one that matches your braking setup (disk front drum rear unless you swapped to rear disks) you should be good Link to comment Share on other sites More sharing options...
kook911 Posted February 1 Author Share Posted February 1 Did the XJ ever come with factory disc rears? Checking rockauto shows drums for all the years of XJ. Link to comment Share on other sites More sharing options...
GonzoTheGreat Posted February 1 Share Posted February 1 12 minutes ago, kook911 said: Did the XJ ever come with factory disc rears? Checking rockauto shows drums for all the years of XJ. Rear drums from 84 to 01. There was never a rear disc option. I've been running an XJ proportioning valve in the daily with no issues. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted February 1 Share Posted February 1 No XJ rear disks at least none that I know of. ZJ had rear disk options. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 1 Share Posted February 1 Don't use the XJ prop valve. Eliminate the distribution valve, connect the 2 front lines together, run one brake line to the rear with an adjustable prop valve. Link to comment Share on other sites More sharing options...
GonzoTheGreat Posted February 1 Share Posted February 1 1 hour ago, cruiser54 said: Don't use the XJ prop valve. I’ve heard this argument. Can you explain? Is the risk that it would lock up the rear too easily on an MJ with an empty bed, being proportioned for the heavier rear body of an XJ? Link to comment Share on other sites More sharing options...
acfortier Posted February 1 Share Posted February 1 My truck has a YJ prop valve, no issues braking/locking up, ever. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted February 1 Share Posted February 1 2 hours ago, GonzoTheGreat said: I’ve heard this argument. Can you explain? Is the risk that it would lock up the rear too easily on an MJ with an empty bed, being proportioned for the heavier rear body of an XJ? I’m curious as well Link to comment Share on other sites More sharing options...
87MJTIM Posted February 1 Share Posted February 1 1 hour ago, ghetdjc320 said: I’m curious as well Link to comment Share on other sites More sharing options...
kook911 Posted February 1 Author Share Posted February 1 7 hours ago, cruiser54 said: Don't use the XJ prop valve. Eliminate the distribution valve, connect the 2 front lines together, run one brake line to the rear with an adjustable prop valve. I know there are many ways doing this. I went out and bought the 95/96 mc/booster, so I’m ready to install this in the truck. If there is a solid reason to go the other way please let me know. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2 Share Posted February 2 Use a dual diaphragm booster if you like. It's a great upgrade and there are a few ways to do it. More on that later. So, the inside diameter of your MJ and XJ's brake lines is .100" The MJ distro block passages are .050"!! Quite a restriction. That thing has to go. It is very easy to just couple the front lines together and use one of the lines from the master cylinder that go to the rear axle from the master, to an adjustable prop valve and on out the back. You don't have to fight rusty fittings. Changing/swapping a prop valve can be a real bear Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2 Share Posted February 2 I prefer using the 99 to 2004 Grand Cherokee booster/master for a few reasons. One is the fact that the mounting studs are a smaller diameter than the original. That's a big deal when you go to put it back together. There's a metal plate that shifts upon removal of the original booster. Makes it a b*@ch to get a booster in with the big studs. The master comes with FLEXIBLE brake lines off the master. All you have to do is cut the solid ends of those "hoses", flare them to the factory plumbing and it all goes together easily. No fighting/bending/cussing. There is a commonly available brake light/torque converter cut out switch that bolts right in. You don't have to grind the brake rod to fit the old style switches. The 99 to 2004 booster/master is easy to find in junkyards. Link to comment Share on other sites More sharing options...
87MJTIM Posted February 2 Share Posted February 2 So why not use a XJ prop valve IF you eliminate the load valve and switch to disk brakes? Link to comment Share on other sites More sharing options...
GonzoTheGreat Posted February 2 Share Posted February 2 17 minutes ago, cruiser54 said: So, the inside diameter of your MJ and XJ's brake lines is .100" The MJ distro block passages are .050"!! Quite a restriction. This is the hard data I was hoping for. Thanks @cruiser54!! Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2 Share Posted February 2 18 minutes ago, 87MJTIM said: So why not use a XJ prop valve IF you eliminate the load valve and switch to disk brakes? You can do that if you wanna mess with the XJ prop valve. But, then you need to grab the "guts" of a 1994 to 1998 ZJ prop valve because of the discs. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2 Share Posted February 2 10 minutes ago, GonzoTheGreat said: This is the hard data I was hoping for. Thanks @cruiser54!! Link to comment Share on other sites More sharing options...
kook911 Posted February 2 Author Share Posted February 2 Cruiser wonderful information and I should had asked before I went out and grabbed one from a junkyard. Since I can’t return it I will go through with the XJ master booster and proportioning valve. Will the MJ factory brake lines screw into the XJ valve without any modifications? Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2 Share Posted February 2 They're the correct threads, but you better be sure each line goes into the correct place. those valves are different MJ to XJ. You can always NOT use the factory prop valve and still use your early booster/master. Link to comment Share on other sites More sharing options...
Salvagedcircuit Posted February 2 Share Posted February 2 3 hours ago, cruiser54 said: There is a commonly available brake light/torque converter cut out switch that bolts right in. You don't have to grind the brake rod to fit the old style switches. Another alternative is to use a brake pedal from a 96+ that has provisions for the new style brake light switch. I did that on mine and other than having to probe out the connector to determine the right contacts, the brake light switch works so much better than the original '88 brake light switch. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted February 2 Share Posted February 2 4 hours ago, 87MJTIM said: So why not use a XJ prop valve IF you eliminate the load valve and switch to disk brakes? Drum brakes require less pressure before locking. The whole purpose of a prop valve it to correctly distribute the pressure to keep the rear from locking before the front. On a truck, it makes sense to have a varying or adjustable prop valve as the bed weight will always be a rather large variable. The ZJ valve for a 4 wheel disk setup will allow a higher pressure pass through for rear disks. There are also many more factors at play with a hydraulic braking system. Link to comment Share on other sites More sharing options...
kook911 Posted February 2 Author Share Posted February 2 4 hours ago, cruiser54 said: They're the correct threads, but you better be sure each line goes into the correct place. those valves are different MJ to XJ. You can always NOT use the factory prop valve and still use your early booster/master. Cruiser I’m assuming that this pic is correct? Link to comment Share on other sites More sharing options...
cruiser54 Posted February 2 Share Posted February 2 I don't know off the top of my head as I don't use the prop valves. I've been doing rear disc brake conversions on numerous models of cars for decades and just use the adjustable prop valves. Only on an 88 XJ with a rear disc conversion did I use the factory prop valve. I ran it in stock configuration with rear discs and then swapped the ZJ guts in to see if it was better. It was. Link to comment Share on other sites More sharing options...
kook911 Posted February 2 Author Share Posted February 2 Ok now the next problem is that I believe the lines are rusted by the threads. Even under the truck by the LSV they are not breaking free. Will this be a cut the lines and redo the entire lines? Link to comment Share on other sites More sharing options...
Salvagedcircuit Posted February 2 Share Posted February 2 1 hour ago, kook911 said: Ok now the next problem is that I believe the lines are rusted by the threads. Even under the truck by the LSV they are not breaking free. Will this be a cut the lines and redo the entire lines? It looks like you already soaked them in penetrant, but make sure to use brake line wrenches. They do provide a lot more leverage on those tiny annoying brake line fittings. Link to comment Share on other sites More sharing options...
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