Prop valve question

truck7575 · Feb 27, 2011

I have a 8.25 with ZJ disc brakes in the back and a ZJ brake booster and WJ knuckles and brakes. What is the best proportioning valve with what mOdification to use. I currently hav my 86 XJ wagoneer prop valve installed and I also have the ZJ valve to. Do I need a WJ valve or can I mod or use one that I already have to get my brakes to work right?

nochance9 · Feb 27, 2011

Adjustable one. Lots of people make them. That way you can dual it in exactly how you want it.

cruiser54 · Feb 27, 2011

nochance9 said:
Adjustable one. Lots of people make them. That way you can dual it in exactly how you want it.

There's your answer. With all your other brake mods, everything else is a crap shoot.

I've converted numerous vehicles to rear disc and this works the best. You'll end up using a union to tie the two front lines together where the prop valve used to be. Then put the adjustable valve to tie the two rear lines together and have adjustability.

robsjeepxj · Feb 27, 2011

I just bypassed the valve altogether for the rear, works fine for me.

CharlesS · Feb 27, 2011

In 2000 I converted the Corp 8.25 in my '98 to disc brakes, reused the brake booster and master cylinder. Just remove the O ring from the shuttle valve inside the proportioning valve which will provide equal pressure to front and rear brakes.
This setup has work very well for the past 11 years....

Note: This modification to the proportioning valve should not be done to XJs that have tires smaller than 31" otherwise the rear brakes may have a tendency to grab harder than the fronts....

nochance9 · Feb 27, 2011

CharlesS said:
In 2000 I converted the Corp 8.25 in my '98 to disc brakes, reused the brake booster and master cylinder. Just remove the O ring from the shuttle valve inside the proportioning valve which will provide equal pressure to front and rear brakes.
This setup has work very well for the past 11 years....

Note: This modification to the proportioning valve should not be done to XJs that have tires smaller than 31" otherwise the rear brakes may have a tendency to grab harder than the fronts....

I first used the ZJ prop valve in mine with ZJ rears. That was better than the XJ one. But then I removed the o ring, that worked much better, except the rears would lock up before the fronts. (with 35s) and ideally you would have them lock up at the same time. That's why the adjustable one is the best option. Imo and they're not all that much dough either.

truck7575 · Feb 27, 2011

thanks for all the good ideas keep'm coming

Gaius · Feb 27, 2011

Mine is a 98, so I'm sure the combo valve is a different style. But I swapped in the ZJ pin and spring into the XJ valve, and with WJ fronts and ZJ rears the balance is superb.

truck7575 · Mar 2, 2011

what was wrong with the braking before you changed the pin and spring? What was it doing to make you need to change it out?

c0ncEpT · Mar 3, 2011

Fronts lock up way before the rears with ZJ discs and stock XJ valve. I have to push the brake pedal as hard as I can even on snowy roads to get the rears to lock up.

Prop valve question

truck7575

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nochance9

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cruiser54

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robsjeepxj

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CharlesS

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nochance9

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truck7575

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Gaius

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truck7575

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c0ncEpT

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