Brake system questions regarding blown hose

Mod tech since I have an 8.8 in the rear. I did not make any changes to the prop valve, etc. I haven't been real happy with the braking performance since I've done the swap.

Here's my new question/scenario... Yesterday I blew a front brake line while exiting the interstate. Now that I've been thinking about it and reading up I believe with an unmodified system that the rear brakes should have still received brake pressure and would have helped get me stopped. I had some pressure, but very very little and I had no comfort that I was going to be able to stop before the red light I was approaching. Fortunately I did using the tranny and gears to engine brake. So, I'm thinking that my rears are seriously not getting enough pressure to be effective in the least.

I'm going to make a run to NAPA to get some parts to fix the front line, etc. Should I think about pulling the o-ring in the prop valve? Will that help the rear performance based on what I explained? I understand by doing this that you lose the backup capability/separation between front/rear in case I have a problem like before. Would swapping in the internals of the ZJ valve be better and retain all of the safeties?

So, it seems that I need to do something about the prop valve. I replaced my blown hose, gravity bled all four corners, and removed the o-ring/grommet thingy in the prop valve.

Now the rear tires lock up without too much hassle. I've never been able to hear even the slightest hint of lockup, front or rear. I should've mentioned before that I'm on 35s with an '01 XJ. So I've clearly seen a result and I'm starting to feel better. I think I'm gonna look into the ZJ guts to put into my valve. I'd rather have a more proper bias and split system safety.

So I see tons of threads out there and people are split between doing something with the proportioning valve or just leaving it alone. Well, I now know that I had/have to do something with it to get braking that I'm comfortable with. Now I won't be so nervous on steep declines out on the trail. Before I felt like I couldn't keep the truck from rolling out from under me on steep pitches.

It is my understanding that with the 0 ring removed, a loss of function up front will affect the rear too. Additionally, be careful your rear doesn't lock prematurely and spin the vehicle under braking load. I had that problem with 50/50 pressure distribution.

Yeah, I understand. I was mainly looking for a result and then go from there. I now know that I need a mod to the prop valve for my application. I'm not going to leave it like this for the two reasons you mentioned. I at least now know that the prop valve should give me the results I'm looking for. Now I'm on the lookout for a ZJ valve to swap the guts and see how that does.

Dim memory of someplace selling ADJUSTABLE Prop valves.
Might get lucky if you try a quick google or other search.

Good Luck,
Orange

madmike283 said:

Yeah, I understand. I was mainly looking for a result and then go from there. I now know that I need a mod to the prop valve for my application. I'm not going to leave it like this for the two reasons you mentioned. I at least now know that the prop valve should give me the results I'm looking for. Now I'm on the lookout for a ZJ valve to swap the guts and see how that does.

Click to expand...

SSBC sells a distribution block with an adjustable prop valve and an adjustable in-line prop valve.

I can't make hardlines myself, I asked a mechanic to do the lines for the SSBC distribution block and they basically refused, thinking the in-line valve was just as good, and conferring with a dealer mechanic who owns several lifted XJs and ZJs, we put the in-line valve on the common hardline to the rear on the unibody rail. If you plan on doing rocks, you may want to find a better location. By that point my brake setup had gone to poop and I'm not really sure how that affected the system. The ZJ internals swap did not work for my application...not enough rear pressure...and with a 50/50 flow I came >this< close to rolling the Jeep in an emergency stop. At the moment my brakes are screwed though and I have almost no pressure up front and no pressure at all in the rear. I need to try a few combinations and new parts when I get home this summer.