ncgamedog Posted September 28, 2009 Share Posted September 28, 2009 The parts XJ I have is a 96 that I'm robbing the AX-15/231 from. As I understand it, the 96 has a dual diaphragm booster. Would this be a bolt on mod for my 91' MJ ? It seems like my rear brakes w/ the 35 arent doing a whole lot and would enjoy some better braking. Right now its just stock and the brakes are pretty poor. The pedal is plenty firm and has a short throw, it feels fine, just takes alot of effort to get it slowed down in a hurry. I read somewhere that I can adjust the rear prop valve by lengthing the rod to apply a little more rear bias, but I figured while I'm swapping parts over it would be a good time to upgrade since I already have the parts. That is if its an easy swap, I don't have a lot of wiggle room in my budget for extra small stuff beyond what its going to cost me to get the 4wd swap up and running. thanks again guys -Justin Link to comment Share on other sites More sharing options...
HellCreek Posted September 28, 2009 Share Posted September 28, 2009 Hi, Justin, Yes - do it. I just finished the swap on my 1989, and you would not believe the difference it makes. A bit of warning, though; after the swap, go easy on the brakes until you get used to them. They will lock up easily, if you apply them like you are used to with your current setup. Also, you will need the 1/4" spacer from your donor vehicle that goes between the booster and the firewall. -Tom Link to comment Share on other sites More sharing options...
ncgamedog Posted September 28, 2009 Author Share Posted September 28, 2009 cool! So no worries with the push rod adjustment or anything? Any brake line mods? Sounds like no, but just want to double check. thanks Link to comment Share on other sites More sharing options...
offroader461 Posted September 28, 2009 Share Posted September 28, 2009 you WILL need to either modify you stock brake light switch or use the late model one if there is a spot on the pedal assembly for it and you WILL need to make new brakes lines b/c the fittings on the master cylinder for the late model won't match up plus you need longer brake lines from the master cylinder to the proportioning valve anyways Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 29, 2009 Share Posted September 29, 2009 you WILL need to either modify you stock brake light switch or use the late model one if there is a spot on the pedal assembly for it and you WILL need to make new brakes lines b/c the fittings on the master cylinder for the late model won't match up plus you need longer brake lines from the master cylinder to the proportioning valve anyways Since you're installing the 96 booster/master in a 91 MJ you already have the "new style" brake switch - no mods necessary. There are no mods necessary for the booster-to-pedal rod either; just bolt it on to the brake pedal. You may have to buy a new retainer clip for the booster rod as it's hard to get them off w/o destroying them. You will have to fab the new brake lines from the new master to the existing combination (not a proportioning) valve though. :cheers: Link to comment Share on other sites More sharing options...
ncgamedog Posted September 29, 2009 Author Share Posted September 29, 2009 sounds like just cut the old ends off and add new one and re-flare the lines on maybe some short extensions on the existing lines? NAPA has unions for brake lines i'm pretty sure... Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 29, 2009 Share Posted September 29, 2009 I wouldn't use a union on brake lines. When I did mine, I saved the fittings from the 96 master, already had the combo valve fittings, so I just purchased a 2' length of 3/16" tubing and bent new lines and reused the original flare fittings. You will have to move the windshield washer bottle forward about an inch too for clearance, or install a 97+ washer bottle inside the fender liner like I did. Link to comment Share on other sites More sharing options...
akamcbird Posted September 30, 2009 Share Posted September 30, 2009 you WILL need to either modify you stock brake light switch or use the late model one if there is a spot on the pedal assembly for it and you WILL need to make new brakes lines b/c the fittings on the master cylinder for the late model won't match up plus you need longer brake lines from the master cylinder to the proportioning valve anyways Since you're installing the 96 booster/master in a 91 MJ you already have the "new style" brake switch - no mods necessary. There are no mods necessary for the booster-to-pedal rod either; just bolt it on to the brake pedal. You may have to buy a new retainer clip for the booster rod as it's hard to get them off w/o destroying them. You will have to fab the new brake lines from the new master to the existing combination (not a proportioning) valve though. :cheers: what years did they change to the "new style" brake switch? and what years are mods necessary for the booster-to-pedal rod? and can the combination valve be swapped for the xj prop valve? (assuming the height sensing valve were removed and the lines were run like the xj) ...does this thought make sense? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 30, 2009 Share Posted September 30, 2009 what years did they change to the "new style" brake switch?? 1991, HO start year and what years are mods necessary for the booster-to-pedal rod?? 1990 and below and can the combination valve be swapped for the xj prop valve? (assuming the height sensing valve were removed and the lines were run like the xj) ...does this thought make sense? Yes. Link to comment Share on other sites More sharing options...
akamcbird Posted September 30, 2009 Share Posted September 30, 2009 i knew youd have the answers. thanks not what i wanted to hear for the first two but thanks Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 6, 2009 Share Posted October 6, 2009 bringing back an old thread here, for all you renix guys... what did you do to fix the brake pedal being REALLY high, my brake pedal is now about 3 inches further up than my clutch pedal. anyone else have this issue? Link to comment Share on other sites More sharing options...
jpnjim Posted October 6, 2009 Share Posted October 6, 2009 I think this is where the spacer comes in. I'm actually looking for some enlightenment on this too. :smart: I bolted up a 2001 XJ MC & booster, and have the high pedal. It modified the old pedal arm to fit, and to activate a Ford truck style brake light switch (I had one, and was able to force the electrical connection in there :yes: ). I still have the 2001 brake arm, and took measurements off it, I just haven't gotten around to figuring out how my 88's is different, and where things went wrong. I'm guessing I may have to move the attachment hole on the pedal arm, or find a 1/4" spacer from a 91-96 (guessing :dunno: ) XJ. Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 7, 2009 Share Posted October 7, 2009 i already have the 1/4 inch spacer installed, i think the rod itself it to long, needs to be shortened, just wondering how others have gone about shortening it? Link to comment Share on other sites More sharing options...
offroader461 Posted October 7, 2009 Share Posted October 7, 2009 i have the dual booster in my 87....bolted up perfect...pedal is exactly where it was b4 Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 7, 2009 Share Posted October 7, 2009 mine is from a 99, does this make a difference? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 7, 2009 Share Posted October 7, 2009 mine is from a 99, does this make a difference? Yep. The 97+ booster to pedal rod length is way too long, your old booster rod needs to be refitted to your 99 booster. Or get the 95-96 booster and be done with it. Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 7, 2009 Share Posted October 7, 2009 ahh, this is merely an opportunity to create an adjustable rod... :idea: thanks for the info! Link to comment Share on other sites More sharing options...
HellCreek Posted October 7, 2009 Share Posted October 7, 2009 The length of the single diaphragm booster rod is 4-7/8" from the mounting flange of the booster to the center of the booster rod eye. The length of the '95-'96 booster rod is 5-1/4" measured the same way, so you need the 1/4" spacer. I actually made mine out of 3/8" aluminum to get the new one exactly the same as the old one. -Tom Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 8, 2009 Share Posted October 8, 2009 The length of the single diaphragm booster rod is 4-7/8" from the mounting flange of the booster to the center of the booster rod eye. The length of the '95-'96 booster rod is 5-1/4" measured the same way, so you need the 1/4" spacer. I actually made mine out of 3/8" aluminum to get the new one exactly the same as the old one. -Tom yeah, that'd be fine if i were using a 96 booster ;) mine's from a 99 and i already have the spacer installed. i'll just have to shorten the rod. thanks guys Link to comment Share on other sites More sharing options...
ncgamedog Posted October 10, 2009 Author Share Posted October 10, 2009 and can the combination valve be swapped for the xj prop valve? (assuming the height sensing valve were removed and the lines were run like the xj) ...does this thought make sense? Yes. about to start on the swap this week. I was looking at the lines under my truck and it looks like there are 2 lines from the combo valve running to the rear of the truck, one hits a T and jumps over to the soft line/hose, the other runs to the prop valve. I think I will either try to use the XJ prop valve or just eliminate one of the lines and plug off the port on the MJ combo valve. Does the XJ prop valve also have 2 outlets for the rear brakes? I don't see why I can't use one of the existing rear lines running back to the rear pluged into the XJ valve...any input? Link to comment Share on other sites More sharing options...
Pete M Posted October 10, 2009 Share Posted October 10, 2009 One of the MJ lines goes to the rear prop valve, the other is the emergency bypass line that bypasses the rear prop valve in the event of a loss of front brakes. When I installed the 95 booster in my 90, I used the matching XJ prop valve and ran a single line to the rear (all new lines since I don't trust 20 year old steel under a michigan truck). Link to comment Share on other sites More sharing options...
ncgamedog Posted October 10, 2009 Author Share Posted October 10, 2009 boy, I don't blame you there. My lines still look like new though, I prefer to replace them but looks like a pain to get at them behind the gas tank. If they still work I may just try to reuse one. Link to comment Share on other sites More sharing options...
ncgamedog Posted October 10, 2009 Author Share Posted October 10, 2009 i need some help guys! i am out here getting ready to pull this booster and master and this 96 has ABS...does this make a difference for the XJ prop valve? I plan to use the XJ prop valve too. i want to make sure before i waste my time. thanks! so will a booster,master, and prop valve from a 96 XJ with ABS work right for this swap? Link to comment Share on other sites More sharing options...
ncgamedog Posted October 11, 2009 Author Share Posted October 11, 2009 any one? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 11, 2009 Share Posted October 11, 2009 I used a 96 booster/master from an XJ w. ABS in my 91, but kept my original MJ combination valve and load sensing valve. I don't see any reason why it should not work using the XJ prop valve either as long as the ports are the same as non-ABS. Link to comment Share on other sites More sharing options...
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