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Load sensing brake prep. valve. upgrade/removal?

tbburg

tbburg

NAXJA Forum User
Location
Scottsdale AZ
I'm looking at upgrading the brake mstr. cyl./booster to the late model Cherokee dual diaphragm assembly. While I'm in there, I want to do away with the load-sensing valve and do away with the extra plumbing. (Mainly to reduce complexity - it's in a race truck)

The current idea is to install an adjustable proportioning valve through the firewall, with the knob run through the dash for in-truck adjustment, but I'm open to other ideas.

'Curious if anyone else has removed the load sensing system, what you used, and how it's worked out.

Edit: Not much difference, but '88, 4.0, AW-4 - have to keep the rear drum brakes(rule book requirement).
 
tbburg said:
I'm looking at upgrading the brake mstr. cyl./booster to the late model Cherokee dual diaphragm assembly. While I'm in there, I want to do away with the load-sensing valve and do away with the extra plumbing. (Mainly to reduce complexity - it's in a race truck)

The current idea is to install an adjustable proportioning valve through the firewall, with the knob run through the dash for in-truck adjustment, but I'm open to other ideas.

'Curious if anyone else has removed the load sensing system, what you used, and how it's worked out.

Edit: Not much difference, but '88, 4.0, AW-4 - have to keep the rear drum brakes(rule book requirement).
Click to expand...

Talk to Dustin (Torx) about rerouting the line, he did a line lock in the center console so the routing would be similar for a proportioning valve.
 
The info is in here, somewhere, as I found it once before.

Essentially you remove the MJ proportioning valve (2 rear going outputs) and replace it with an XJ one (1 rear going output). At the ride height valve, you take the line you attached to the XJ valve and use it to run the rear brakes. The other line you abandon (or remove all together).

This takes care of two issues. Dealing with the ride height valve when you lift, and trying to get all the air out of that OEM system if you open it.

Ron
 
Similar to what Ron said, I put an XJ master, booster, and prop valve into my Mj when I had it, and just did away with the load valve all together.
 
GrimmJeeper said:
Similar to what Ron said, I put an XJ master, booster, and prop valve into my Mj when I had it, and just did away with the load valve all together.
Click to expand...

Hey Mike. Wanna help me put a ZJ prop valve in my truck? I'll pay in $$ or beer, or both.
PHP:
 
if you want to bring it to me, no problemo. i have everything we would need here (parts excluded of course)
 
Of course I'd come to you. :) Make me a parts list. Or better yet, if you could pick the parts up from work, I'll reimburse you. Let me know. Thanks.
 
prop valve is not available aftermarket, gotta find one of those yourself. only other thing we would need is a couple of hard lines and unions. I would have to look at your MJ to see what we need, I did the swap over a year ago and don't have an MJ anymore to look at :bawl: The parts we need are readily available at any parts store though. Shoot me a PM and we'll work out the when, maybe do a writeup in the process? you can sit in a chair and take pics while I get to work :D
 
Sounds good. I already have a 4-disc ZJ prop valve in my tool box. Cracker was gonna help me out, but he's always out of town and he lives too far away. :laugh3: PM coming.
 
johnnyc said:
Sounds good. I already have a 4-disc ZJ prop valve in my tool box. Cracker was gonna help me out, but he's always out of town and he lives too far away. :laugh3: PM coming.
Click to expand...

:eyes:
 
i got an adjustable prop valve from Summit Racing and have it mounted under the hood near the master cylinder. i really dont tow much so i dont need to mess with it much, but its great for fine tuning.
 
89eliminator said:
i got an adjustable prop valve from Summit Racing and have it mounted under the hood near the master cylinder. i really dont tow much so i dont need to mess with it much, but its great for fine tuning.
Click to expand...

can I get some more info on this Wade? I need to ditch the MJ proportioning valve and redo all of my brake lines.
 
Got the ZJ 4-disc prop valve installed thanks to Mike (Grimmjeeper). It went pretty smoothly...except for some really stubborn brake line fittings. :) Looks a lot cleaner under there with that load-sensing valve gone.
 
Any time Johnny, bring it back by sometime after socal fest so I can replace that fitting in the back, it's pretty thrashed you don't want to have that thing cause you problems later on down the road.
 
For what it's worth I took the load link off the rear valve and adjusted it till I got decent rear brakes on my '91 MJ. I then took the arm off and reinstalled it lined up with the valve and zip tied it so it wouldn't adjust itself. Been driving it that way for 5 years and wish I had done it sooner. I had planned on doing a dash mounted adjustable proportioning valve but it stops so much better I can't bring myself to mess with it. I was the service manager at the local jeep dealer when these were new and my Chrysler district service rep and I spent a good deal of time trying to get these trucks to stop good enough for our customers. I think that the poor braking was the reason they quit building them.
 
Under extreme hard braking, the load sensing prop valves have been known to explode. Remove them at your earliest convenience.
 
Under extreme hard braking, the load sensing prop valves have been known to explode.
===========================================================
Dam I'm using one in my XJ as a adjustable proportioning valve. Mostly for towing. Hand adjusted with 2 setting empty/loaded. Sort of glad I didn't know that coming down the mountains.
========================
If you stuck with drums? Some XJ with 44 had 10 ". Do they have to be stock drums or will any drum will do. Maybe adapting some.
 
Technically, the brakes have to be "Stock, available as a factory option" You can swap in brakes offered on the SUV version of a truck(Durango brakes on a Dakota, Explorer brakes on a Ranger, etc.) Which means I can use stock Cherokee brakes on a Comanche, woo-hoo, so exciting,.... Master cylinder/booster/proportioning valve is open.(may be modified or replaced)

I've argues with my co-driver about weather we could get away with Grand Cherokee brakes, which MIGHT be a grey area. Getting disqualified is not a great way to find out, and of course asking is a great way to be told no,... (the old "better to ask for forgiveness then ask for permission" thing doesn't work as well when the entry fee is $1500.00)
 
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