load proportioning sensor

[codybutz]

On the d35 that is in the rear of my 87 long bed, I have one of those load proportioning valves. I'm not sure if it works properly or not. Is there a way to tell? If it is not working is there a way to bypass it or get rid of it? Can I just plug the lines that are running to it? Thanks in advance. - Cody

[cracker]

That is your proportioning valve for the complete vehicle. They have been known to explode under extreme braking conditions too.

 

In order to remove it, you must put a true proportioning valve under your hood and remove the one one that looks like it is a proportioning valve.

 

Many folks, including myself, use a regular cherokee prop valve after we remove the load sensing one.

[codybutz]

well nobody needs/wants an exploding rear end :rotfl2: so how do i go about doing this? anybody have a write up? and tips or tricks? can I grab all the parts i need at a junk yard?.

[cracker]

well nobody needs/wants an exploding rear end :rotfl2: so how do i go about doing this? anybody have a write up? and tips or tricks? can I grab all the parts i need at a junk yard?.

 

I am sure someone did a write up on it. Just do a search for that.

 

On the front you can go to the yard and pull a cherokee prop valve and it is pretty simple swap. You will have to note which lines the cherokee used and emulate the same line on your MJ (yes, you will have an extra one not being used.)

 

You'll have to crawl under the rear and figure out what you want to do. There is a 'T' back there so I plugged one of the holes and used the short tube to extend down the bracket that holds the speed sensing valve and from there I run a flexible line to the axle. Note that there is two brake lines running from the front to the back. You will only use one of them in so make sure it is the one you connected on the front.

 

Overall this is a pretty simple thing to do. Just take your time.

[johnnyc]

So Cracker, when are you gonna help me do mine? :D

[cracker]

So Cracker, when are you gonna help me do mine? :D

 

When ever you have the time :cheers:

[Backroads]

That is your proportioning valve for the complete vehicle. They have been known to explode under extreme braking conditions too.

 

In order to remove it, you must put a true proportioning valve under your hood and remove the one one that looks like it is a proportioning valve.

 

Many folks, including myself, use a regular cherokee prop valve after we remove the load sensing one.

 

I'm gonna disagree with that.

 

I removed my 'load valve' ran a new hardline from the front of the stock MJ distribution valve (unsure of proper term) and then plugged the bottom front plug. I also have a WJ master cylinder and booster up front. Add brand new EVERYTHING to the rear brakes and its not the least bit trouble some or dangerous. My brakes are AMAZING compared to the nothing I had before. In fact they are almost better than the ones on my cherokee.

 

IMO its not necessary to change 'prop' valves out. I'm sure it doesnt hurt anything, but its not the only way.

[Eagle]

That is your proportioning valve for the complete vehicle. They have been known to explode under extreme braking conditions too.

True. Like mine, for example.

 

In order to remove it, you must put a true proportioning valve under your hood and remove the one one that looks like it is a proportioning valve.

Untrue. You may do so if you wish, but I didn't and I'm not sorry.

 

The "replacement" is an XJ proportioning valve. If you study how it works, you'll see that it provides NO advantage in an MJ. The MJ height-sensing valve reduces rear brake force when the truck is unloaded in order to alleviate premature rear brake lockup -- which causes spin-outs in panic stop situations. The XJ proportioning valve reduces rear braking force when the brakes are used lightly, until the pressure rises high enough to move the spring-loaded plunger, after which you get full braking to the rear. So in a full panic stop, the XJ proportioning valve will NOT reduce rear braking force, and will NOT prevent premature lock-up under the exact conditions when you most need it to be prevented.

 

Many folks, including myself, use a regular cherokee prop valve after we remove the load sensing one.

And many others, including myself, do not. Some others prefer to use a mechanically-adjustable Wilwood proportioning valve, and IMHO that is far better than the XJ gizmo that reduces the rear braking when it shouldn't, and doesn't reduce it when it should.

[johnnyc]

So Cracker, when are you gonna help me do mine? :D

 

When ever you have the time :cheers:

 

Tomorrow afternoon? :D

 

Since I put rear discs on, I picked up a prop valve from a 4-wheel disc ZJ. This should work okay, shouldn't it?

[codybutz]

ok so this has now blown my mind. Could i get away with just plugging the lines to this thing and not using it at all and still have breaks? Also the breaks seem to work so is it safe to assume this thing works as well? or do i need to load down the bed and then see if i have breaks?

[cracker]

I stand corrected then. It was my understanding that the 'prop valve' under the hood was a slave to the true prop valve in the rear. :dunno:

[cracker]

So Cracker, when are you gonna help me do mine? :D

 

When ever you have the time :cheers:

 

Tomorrow afternoon? :D

 

Since I put rear discs on, I picked up a prop valve from a 4-wheel disc ZJ. This should work okay, shouldn't it?

 

Yeah. That'll go right in there. Tomorrow afternoon would be fine. I am working hard on my rig but I can guide you through stuff and help out.

 

Give me a text when you want to come up and I'll confirm the time.

[Eagle]

ok so this has now blown my mind. Could i get away with just plugging the lines to this thing and not using it at all and still have breaks?

Cody, it's B-R-A-K-E-S, not B-R-E-A-K-S.

 

The answer is "Yes." There is no reason to do any more work than necessary. Rip out BOTH old lines going from the front to the rear. One of them comes out of the "nose" of the distribution block (it is not a proportioning valve in the MJ), the other comes out of the forward outlet on the bottom.

 

Plug the old outlet on the forward/bottom of the distribution block. All you need to plug it is a 1/2x20 (fine thread) bolt. To make it neat, saw off the threaded shank to allow the head to seat against the body of the distribution block. I used a 1/2" O-ring under the head to seal it.

 

Run ONE new line from the "nose" outlet of the distribution block to the rear of the truck and connect it directly to the upper end of the rear axle flex hose.

 

Bleed the brakes.

 

Drive.

 

You can leave the abandoned body of the rear height sensing valve on the chassis, or take it off and throw it away. If yours hasn't failed yet, you might want to keep it in case somebody needs one some day for a fully accurate restoration project.

[codybutz]

It's hard to be grammatically correct when I'm using the web on my phone and this dam thing auto fills in all my words.

 

But any who, thanks for the info. I'll have to look into this when the jeep is in front of me. Thanks again. - Cody