XJlimitedx99

I have KJ discs on my 8.25 with stock 30 brakes up front. I swapped to the ZJ prop valve internals when I did the disc swap. Found that to work well.

I recently installed a Durango master cylinder (1.125") in preparation for larger brakes up front. Check my build thread for specifics.

Keep in mind that your braking force will decrease with the larger MC compared to the smaller one with the same amount of force on the pedal. The purpose of the larger MC is solely to move more fluid into larger calipers, i.e. maintain a similar pedal travel/feel as factory.

Just now thinking about how I may want to go back to XJ prop valve internals after doing big brakes up front to keep the ratio in check. Guess time will tell!

jaredalv

I did the crown auto kit (for sake of times savings). I bought a ZJ prop valve off ebay and swapped the internals. This route felt much better than pulling the o-ring.

Jim Malcolm

For 91-94 XJs, the 95-96 XJ Booster swap has the added benefit of being bolt-in; the brake switch is the same through 96, no modifications to the part required. Biggest issue is finding or making the 1/4" spacer. If you look at the crown kit jaredalv references, you'll see that it comes with the spacer. They're selling you a 95-96 Booster, MC and the spacer... Hardest part of making your own is the big hole in the middle (1-1/2 to 2" range IIRC), but nothing says it has to be steel, a proper grade of plastic would work. Depending on your desired quality level, a stack of washers at each corner and a fat bead of sealant would do the trick. One output on the MC is M10 x 1.0 bubble flare and the other is M12 x 1.0. On the other end, one is 1/4" inverted flare and the other is 5/16", which isn't the easiest to find. I brought the appropriate pre-made "easy-bend" lines at the parts store with the appropriate bubble flares, cut and routed them and then did the inverted flare; little sense doing both.

The "proportioning valve" in a XJ is not a true proportioning valve. Anything you find aftermarket with only 2 ports (in and out) can never be a proportioning valve, there is no connection to the other signal to proportion to. They are a pressure limiting valve, limiting the max pressure that can be applied, typically used on the rears to prevent it from locking up before the front. Yes, you are limiting the maximum performance of your rear brakes if you install one. Most the of aftermarket "combination" valves you'll find aren't a proportioning valve either. There has to be a connection between front and rear to facilitate proportioning, otherwise it's just a limiting valve, either max pressure or min pressure. There are a few OEM applications that have real proportioning valves.

https://www.elcaminocentral.com/thre...estion.188913/
https://www.pro-touring.com/threads/...rtioning-valve

About 1/4 of the way down the page of the below link, Eagle posted a cross-section cut of an XJ valve. To the left is the front inlet/outlet, basically straight through and on the left is the rear.

https://comancheclub.com/topic/54969...g-valve-swaps/

Drum brakes typically have a "residual pressure valve" that holds 2 or so psi of pressure in the rear brake circuits to keep the rear drum mechanism from retracting any further than the drum pushes it once you let off the brakes. The makes the rears quicker to engage than they would otherwise. The other type of valve commonly used in brake circuits is a metering valve; one that requires a certain amount of pressure applied to it before it opens. You'll see a metering valve being used in both of the links I posted of other OEM applications; delaying the application of the front until the rear drums have taken up their slack. Comparing the XJ cross section to that of the other OEM applications, the XJ valve is backwards from a metering valve. I'm having a harder and harder time trying to convince myself that it's anything other than a residual pressure valve. The ZJ has a stiffer spring and a plunger to match, which would seemingly hold more pressure in the rear circuit.

Disclaimer: I have no clue what I'm talking about, just analyzing info available to me and the knowledge I've accumulated over the years. I went straight from single booster w/ drums to the 95-96 booster, accompanying OEM MC, 8.8 discs w/ ZJ valve internals and I have no complaints so I never tried anything else. I encourage corrections and further conversation on this.

robsjeep

OK went to the wrecker today, four WJs to chose from One one of them had the flexible lines on the master, the other three had hard lines with a couple loops of hard line to give some play.

All four had anti skid system.

Now here is my question... Where is the WJ proportioning valve located? I did not see it near the booster. Perhaps it is not on the anti skid equipped WJ? is there a non anti skid WJ option? Is any proportioning done in the antiskid unit? Must I find a non anti skid WJ? or is the WJ valve hiding from me?

Thanks!

cruiser54

My mistake. 94 to 98 ZJ prop valve guts.

robsjeep

Thank you! i will get the ZJ 94 to 98 valve to go with the WJ 99 to 04 booster and master

cruiser54

Just grab the guts from the ZJ. Way easier,