Minuit Posted December 17, 2014 Share Posted December 17, 2014 I've recently gotten my hands on a 95/96 XJ booster and master cylinder. It also came with the distribution block(is that the right name for it?) and I was wondering which one I should use. All of my MJ stuff is present and in good working order including the rear proportioning valve. Thanks. Link to comment Share on other sites More sharing options...
Dando Posted December 17, 2014 Share Posted December 17, 2014 When I installed my 95 booster/cylinder I reused the existing distribution block that was already in my MJ. Like you my rear valve etc all worked properly. Everything has worked great for me so far. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 17, 2014 Share Posted December 17, 2014 The 95/96 XJ block has a proportioning valve built-in that regulates pressure to the rear brakes since XJs did not have the rear load sensing valve. On the MJs rear brakes were biased by the load sensing valve. So if you are retaining this valve, you should use the MJ distribution block (no proportioning). Link to comment Share on other sites More sharing options...
mnkyboy Posted December 17, 2014 Share Posted December 17, 2014 I used the XJ proportioning valve on mine and deleted the stock stuff. It worked ok but my rear disc brakes were overly sensitive, could get real sketchy on gravel roads. My plan is to get an adjustable proportioning valve to fine tune it. Link to comment Share on other sites More sharing options...
Minuit Posted December 17, 2014 Author Share Posted December 17, 2014 Cool, thanks guys. Looks like I'll be using the MJ one then. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 18, 2014 Share Posted December 18, 2014 I used the XJ proportioning valve on mine and deleted the stock stuff. It worked ok but my rear disc brakes were overly sensitive, could get real sketchy on gravel roads. My plan is to get an adjustable proportioning valve to fine tune it. I just swapped the "guts" from a 94 to 98 Grand Cherokee prop valve into my XJ prop valve. Works great, and easy. Link to comment Share on other sites More sharing options...
mnkyboy Posted December 19, 2014 Share Posted December 19, 2014 I had thought of using the ZJ stuff when I had the stockish axles and rear disc, my new axles will have 1 ton brakes (Ford dual piston front, Chevy single piston rear) so I'm thinking I'm going to want some tunability. I imagine the ZJ proportioning would probably work ok with the new set up too though. Link to comment Share on other sites More sharing options...
Incommando Posted December 19, 2014 Share Posted December 19, 2014 I used the xj block, deleted the rear valve, and have excellent brakes with rear drums Link to comment Share on other sites More sharing options...
cruiser54 Posted December 19, 2014 Share Posted December 19, 2014 On the MJ, I have no block and an adjustable prop valve to the rears. Load sensing valve is gone. Just put my front braided brake lines on but haven't driven it. Link to comment Share on other sites More sharing options...
Eagle Posted December 19, 2014 Share Posted December 19, 2014 I've recently gotten my hands on a 95/96 XJ booster and master cylinder. It also came with the distribution block(is that the right name for it?) and I was wondering which one I should use. All of my MJ stuff is present and in good working order including the rear proportioning valve. Thanks. If you have the rear proportioning valve in place and operational, use the original MJ distribution block. The XJ unit is also the proportioning valve, and I can't make myself think of any reason why it would be a good idea to have two proportioning valves in the system, fighting for supremacy. To be honest, the more I think about how the XJ proportioning valve works, the less I like it for ANY application. Link to comment Share on other sites More sharing options...
ggcnash Posted December 20, 2014 Share Posted December 20, 2014 On the MJ, I have no block and an adjustable prop valve to the rears. Load sensing valve is gone. Just put my front braided brake lines on but haven't driven it. Cruiser, so your just coming directly from the M/C? I've been wondering if this was possible, I couldn't see why not since the stock MJ block basically serves as just a T right? Link to comment Share on other sites More sharing options...
cruiser54 Posted December 20, 2014 Share Posted December 20, 2014 I'm not exactly sure how that valve works. I eliminated it. I run from the rear of the master cylinder to the front brake lines and from the front of the master to the rear brake line, with an adjustable prop valve in that line. Link to comment Share on other sites More sharing options...
Eagle Posted December 20, 2014 Share Posted December 20, 2014 Cruiser, so your just coming directly from the M/C? I've been wondering if this was possible, I couldn't see why not since the stock MJ block basically serves as just a T right? Not Cruiser, but the stock metering block (MJ) or proportioning valve (XJ) serves a second function: It's also the actuator for the brake failure warning light. If you eliminate it, you won't have any brake warning system. The way the proportioning function works in the XJ/ZJ version, the forward part of the valve is the part that feeds the rear brake circuit. That plug you see on the front (or nose) of the block has a rubber gasket inside, and there's a brass plunger that has a sliding shank that seals against this gasket. Then there's a heavy spring, and behind the spring there's a flange and a rubber cup seal. At rest, the cup seal blocks brake fluid from going to the rear brakes, so under light braking the fronts do ALL the work. Under severe braking, the hydraulic pressure finally gets high enough to seal the cup in the bore and force the piston forward against the spring. This opens the port to the rear brakes and allows them to do some work. And that's why I don't like the system. There's no danger of spinning out under light braking. Under heavy braking, a lot of weight transfers onto the front wheels, making it harder for them to skid, and OFF the rear wheels, making it easier for them to skid. So what the XJ proportioning valve actually does is not allow the rear brakes to work EXCEPT for the conditions when you really need to limit the braking force to the rear wheels. The other problem with it is that, since the piston only moves under heavy braking (did I mention that the spring is STRONG?), if you drive sanely and never get to panic stop pressures in the system, the cup seal may not move for years. The crud in the brake fluid builds up around it and locks it in place. At that point, you have NO rear brakes -- ever. My '88 XJ hasn't had rear brakes for three or four years. I tested it in snow -- rolling at about 10 or 15 MPH, I opened the door to watch the rear wheels (in a deserted parking lot) and slammed on the brakes. The fronts locked up and skidded. The rears just kept rolling. I think when I get Old faithful back on the road I'll just pull the spring out of the proportioning valve and leave it so I always have rear brakes. I can deal with that. Link to comment Share on other sites More sharing options...
ggcnash Posted December 20, 2014 Share Posted December 20, 2014 Cruiser, so your just coming directly from the M/C? I've been wondering if this was possible, I couldn't see why not since the stock MJ block basically serves as just a T right?Not Cruiser, but the stock metering block (MJ) or proportioning valve (XJ) serves a second function: It's also the actuator for the brake failure warning light. If you eliminate it, you won't have any brake warning system. The way the proportioning function works in the XJ/ZJ version, the forward part of the valve is the part that feeds the rear brake circuit. That plug you see on the front (or nose) of the block has a rubber gasket inside, and there's a brass plunger that has a sliding shank that seals against this gasket. Then there's a heavy spring, and behind the spring there's a flange and a rubber cup seal. At rest, the cup seal blocks brake fluid from going to the rear brakes, so under light braking the fronts do ALL the work. Under severe braking, the hydraulic pressure finally gets high enough to seal the cup in the bore and force the piston forward against the spring. This opens the port to the rear brakes and allows them to do some work. And that's why I don't like the system. There's no danger of spinning out under light braking. Under heavy braking, a lot of weight transfers onto the front wheels, making it harder for them to skid, and OFF the rear wheels, making it easier for them to skid. So what the XJ proportioning valve actually does is not allow the rear brakes to work EXCEPT for the conditions when you really need to limit the braking force to the rear wheels. The other problem with it is that, since the piston only moves under heavy braking (did I mention that the spring is STRONG?), if you drive sanely and never get to panic stop pressures in the system, the cup seal may not move for years. The crud in the brake fluid builds up around it and locks it in place. At that point, you have NO rear brakes -- ever. My '88 XJ hasn't had rear brakes for three or four years. I tested it in snow -- rolling at about 10 or 15 MPH, I opened the door to watch the rear wheels (in a deserted parking lot) and slammed on the brakes. The fronts locked up and skidded. The rears just kept rolling. I think when I get Old faithful back on the road I'll just pull the spring out of the proportioning valve and leave it so I always have rear brakes. I can deal with that. So the MJ block is just a T with a warning light plug for pressure? I do understand that the XJ and ZJ blocks actually proportion the brakes but the MJ does not correct? Link to comment Share on other sites More sharing options...
cruiser54 Posted December 20, 2014 Share Posted December 20, 2014 Cruiser, so your just coming directly from the M/C? I've been wondering if this was possible, I couldn't see why not since the stock MJ block basically serves as just a T right?Not Cruiser, but the stock metering block (MJ) or proportioning valve (XJ) serves a second function: It's also the actuator for the brake failure warning light. If you eliminate it, you won't have any brake warning system. The way the proportioning function works in the XJ/ZJ version, the forward part of the valve is the part that feeds the rear brake circuit. That plug you see on the front (or nose) of the block has a rubber gasket inside, and there's a brass plunger that has a sliding shank that seals against this gasket. Then there's a heavy spring, and behind the spring there's a flange and a rubber cup seal. At rest, the cup seal blocks brake fluid from going to the rear brakes, so under light braking the fronts do ALL the work. Under severe braking, the hydraulic pressure finally gets high enough to seal the cup in the bore and force the piston forward against the spring. This opens the port to the rear brakes and allows them to do some work. And that's why I don't like the system. There's no danger of spinning out under light braking. Under heavy braking, a lot of weight transfers onto the front wheels, making it harder for them to skid, and OFF the rear wheels, making it easier for them to skid. So what the XJ proportioning valve actually does is not allow the rear brakes to work EXCEPT for the conditions when you really need to limit the braking force to the rear wheels. The other problem with it is that, since the piston only moves under heavy braking (did I mention that the spring is STRONG?), if you drive sanely and never get to panic stop pressures in the system, the cup seal may not move for years. The crud in the brake fluid builds up around it and locks it in place. At that point, you have NO rear brakes -- ever. My '88 XJ hasn't had rear brakes for three or four years. I tested it in snow -- rolling at about 10 or 15 MPH, I opened the door to watch the rear wheels (in a deserted parking lot) and slammed on the brakes. The fronts locked up and skidded. The rears just kept rolling. I think when I get Old faithful back on the road I'll just pull the spring out of the proportioning valve and leave it so I always have rear brakes. I can deal with that. So the MJ block is just a T with a warning light plug for pressure? I do understand that the XJ and ZJ blocks actually proportion the brakes but the MJ does not correct? No. Eagle has explained that already. It's actually more complex than an XJ prop valve. Link to comment Share on other sites More sharing options...
Jeep Driver Posted December 20, 2014 Share Posted December 20, 2014 The best single improvement I have made is the dual diaphragm booster, rear discs, discarding the prop valve. I have twice the breaking power of our 97XJ. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 20, 2014 Share Posted December 20, 2014 Cruiser, so your just coming directly from the M/C? I've been wondering if this was possible, I couldn't see why not since the stock MJ block basically serves as just a T right? Not Cruiser, but the stock metering block (MJ) or proportioning valve (XJ) serves a second function: It's also the actuator for the brake failure warning light. If you eliminate it, you won't have any brake warning system. The way the proportioning function works in the XJ/ZJ version, the forward part of the valve is the part that feeds the rear brake circuit. That plug you see on the front (or nose) of the block has a rubber gasket inside, and there's a brass plunger that has a sliding shank that seals against this gasket. Then there's a heavy spring, and behind the spring there's a flange and a rubber cup seal. At rest, the cup seal blocks brake fluid from going to the rear brakes, so under light braking the fronts do ALL the work. Under severe braking, the hydraulic pressure finally gets high enough to seal the cup in the bore and force the piston forward against the spring. This opens the port to the rear brakes and allows them to do some work. And that's why I don't like the system. There's no danger of spinning out under light braking. Under heavy braking, a lot of weight transfers onto the front wheels, making it harder for them to skid, and OFF the rear wheels, making it easier for them to skid. So what the XJ proportioning valve actually does is not allow the rear brakes to work EXCEPT for the conditions when you really need to limit the braking force to the rear wheels. The other problem with it is that, since the piston only moves under heavy braking (did I mention that the spring is STRONG?), if you drive sanely and never get to panic stop pressures in the system, the cup seal may not move for years. The crud in the brake fluid builds up around it and locks it in place. At that point, you have NO rear brakes -- ever. My '88 XJ hasn't had rear brakes for three or four years. I tested it in snow -- rolling at about 10 or 15 MPH, I opened the door to watch the rear wheels (in a deserted parking lot) and slammed on the brakes. The fronts locked up and skidded. The rears just kept rolling. I think when I get Old faithful back on the road I'll just pull the spring out of the proportioning valve and leave it so I always have rear brakes. I can deal with that. Mod it: http://www.lunghd.com/Tech_Articles/Suspension_Steering_Axles_and_Brakes/Proportioning_Valve_Mod.htm Link to comment Share on other sites More sharing options...
Eagle Posted December 20, 2014 Share Posted December 20, 2014 So the MJ block is just a T with a warning light plug for pressure? I do understand that the XJ and ZJ blocks actually proportion the brakes but the MJ does not correct? The MJ distribution block does not act as a proportioning valve, because the rear height-sensing valve takes care of that. BUT ... the MJ distribution block also has a by-pass circuit so that, if the front brakes fail when the rear is unloaded (and therefore getting very little braking through the rear proportioning valve), the bypass circuit sends full pressure to the rear brakes. If you eliminate the distribution block entirely and run direct from the master cylinder, you'll always have full pressure to both the front and the rear. But you won't have any warning light if there's a problem in either circuit. In an unloaded pickup, full pressure to the rear brakes may be too much, and can cause skids and spin-outs. If that's the case, you can buy the Wilwood adjustable proportioning valve and install that in the rear brake circuit. You still won't have a warning light, and if the Wilwood is adjusted for light loads, you won't automatically get increased braking when you load the bed with roof shingles. Link to comment Share on other sites More sharing options...
ggcnash Posted December 20, 2014 Share Posted December 20, 2014 So the MJ block is just a T with a warning light plug for pressure? I do understand that the XJ and ZJ blocks actually proportion the brakes but the MJ does not correct?The MJ distribution block does not act as a proportioning valve, because the rear height-sensing valve takes are of that. BUT ... the MJ distribution block also has a by-pass circuit so that, if the front brakes fail when the rear is unloaded (and therefore getting very little braking through the rear proportioning valve), the bypass circuit sends full pressure to the rear brakes. If you eliminate the distribution block entirely and run direct from the master cylinder, you'll always have full pressure to both the front and the rear. But you won't have any warning light if there's a problem in either circuit. In an unloaded pickup, full pressure to the rear brakes may be too much, and can cause skids and spin-outs. If that's the case, you can buy the Wilwood adjustable proportioning valve and install that in the rear brake circuit. You still won't have a warning light, and if the Wilwood is adjusted for light loads, you won't automatically get increased braking when you load the bed with roof shingles. Understood thank you sir Link to comment Share on other sites More sharing options...
Eagle Posted December 21, 2014 Share Posted December 21, 2014 Mod it: http://www.lunghd.com/Tech_Articles/Suspension_Steering_Axles_and_Brakes/Proportioning_Valve_Mod.htm Removing the spring and pushing the piston permanently forward accomplishes the same thing, and you don't have to worry about the spring. Or I may remove both the spring and the rubber cup washer. Once the cup washer is gone, there's no reason I can think of to keep the spring in there. Link to comment Share on other sites More sharing options...
Bobolink Posted December 22, 2014 Share Posted December 22, 2014 Indeed, Eagle.......is there any reason you can think of to even put the piston back in without the o-ring? Link to comment Share on other sites More sharing options...
Eagle Posted December 22, 2014 Share Posted December 22, 2014 Indeed, Eagle.......is there any reason you can think of to even put the piston back in without the o-ring? Yes. The forward shank of the piston fits into another rubber gasket or bushing. That's open to the "nose" of the block and the forward retainer plug, which has a hole in it. Leave out the piston (plunger), and I think (I'm not certain -- haven't tried it) you'll have a quarter-inch hole for rapidly dumping your brake fluid into the engine compartment. I plan to remove the rubber cup washer from the aft end of the plunger, remove the spring, and manually shove the plunger full forward -- then I'll screw the plug into the valve body and enjoy having rear brakes again. Link to comment Share on other sites More sharing options...
HOrnbrod Posted December 22, 2014 Share Posted December 22, 2014 I don't think that will work. W/o the spring you will have erratic piston problems after you remove the rubber cup. As I see it, you will need the spring to keep a constant bias on the rear brake wheel cylinders. But try it. Link to comment Share on other sites More sharing options...
Eagle Posted December 22, 2014 Share Posted December 22, 2014 I've been driving the '88 MJ with no rear proportioning valve and the MJ distribution block for several years with no issues. The XJ has more weight over the rear axle than an unloaded MJ, so I don't expect any problems there, either. And with the cup washer removed, I don't think the bare piston/plunger can restrict the brake fluid anyway, so I don't think leaving the spring in would create any bias. As I've mentioned before, I was driving for more than 20 years before I owned anything with a proportioning valve, so I'm very comfortable having good brakes when I need them. Link to comment Share on other sites More sharing options...
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