Proportioning Valve Swaps

[ShortBox88]

Hello All,

So I'm new here but have been lurking and finding good info here since I picked up my first Comanche in Aug 2017, finally got round to creating a profile...  I have some questions about the Comanche braking system, I've been reading posts on this forum on this topic as I'm getting ready to lift and axle swap to make sure I'm covering my bases and this one got my attention:

 

https://comancheclub.com/topic/40762-mj-brake-proportioning-valve/

 

There is a good picture of the MJ distribution block cut in half in the linked thread:

My question is why is there no metering valve associated with the front brake circuit?  Am I missing something?  Is it separate from the distribution block on each front brake line?  For a Disk/Drum braking systems I was under the impression that it was important to have a metering valve on the front brake circuit so that the line pressure to the front is delayed such that the rear drums have a chance to apply first since the drum shoes are not in contact with the drum, whereas, the front caliper pads are in contact with the front disk and apply almost instantly when the brake pedal is actuated.  

 

A couple YouTubes on this:

 

https://www.youtube.com/watch?v=qzUk8W1-2pw

https://www.youtube.com/watch?v=tUEsxZGuMk4

 

My second question is related to a statement that 1stDeuce made regarding Wilwood adjustable pressure regulators:

"The Wilwood adjustable pressure regulator that has only one inlet and outlet is often referred to as a prop valve, but it is NOT.  It only functions to limit pressure to an adjustable set point, meaning it'll allow full pressure up to a certain point, then limit it to that pressure no matter how high input pressure goes."

 

I have not been able to find information to support this just doing random Google searches today - Anyone have some insight on what the pressure curve actually looks like for a single inlet/single outlet style aftermarket proportioning valve such as the Wilwood? 

 

I was considering using one of these aftermarket proportioning valves along with the LSV delete procedure outlined in the link below to clean up the braking system a bit and have the valving in place for a rear disk swap later on (which would then likely negate the need {or maybe just my perceived need} for a metering valve on the front brake system):

 

https://comancheclub.com/topic/53274-mj-load-sensing-valve-delete-procedure/

 

However, if the Wilwood single in/out "proportioning valve" is really a pressure regulator that allows full pressure up to a setpoint then flatlines the pressure regardless of the input pressure after that, seems like you'd be leaving some stopping power under-utilized as opposed to a proportioning valve that just affects the slope of the pressure rise curve after the "knee point" or adjustable setpoint.

 

In the interim, my thought is to maybe try using a combination valve off an 80's K-series pickup as I believe I can find one that will have the rear proportioning valve, front metering valve and brake light switch all in one unit and swap that into the Comanche while it is in the disk/drum version and then keep the Comanche distribution block to be used later with the disk/disk, adjustable proportioning valve scenario when I get that project lined up.  Thoughts?

 

Also, 1stDeuce suggested a Jegs part as an alternative to a Wilwood proportioning valve:  http://www.jegs.com/i/JEGS+Performance+Products/555/63025/10002/-1

 

However, I didn't see any description of a metering valve being part of that assembly so maybe a good option for a disk/disk setup but maybe not a disk/drum setup due to the lack of the metering valve???

 

That's all for my first post.  Any help would be appreciated.

[ShortBox88]

7 hours ago, saveevryjp1998 said:

When I went to do a similar swap like you for the first time on my xj years back and a newbie to turning a wrench, not implying you are but me, I was so worried about planning the same thing to the T for the reasons as you since there is so many different ways to do this. For I went back and forth for 6 months stuck contemplating which direction to go while my spare was on blocks on the side of the house brakes out. Then bam 1 day driving my daily 2000 xj my front driver line blew out on the 465 loop in Indianapolis during the start of early afternoon rush hour and no brakes period. The rear didnt work nothing. I hit peddle nothing. Went for e brake and snap. I bobbed weaved and speed up to 75 and back down to 45 looking on how to get safely pulled over. I had my fiance now wife in car too on our way to work our second jobs. It took about 5 miles of white knuckle sphincter clenching before we made it to the perfect off ramp uphill to get us stopped. It dawned on me then the metering valve for the drums is bs. When I got the jeep home that night, before I properly bled the entire system and fixed the line, I pulled it and never looked back. Yes I got lock up at first. Let me tell you it was awesome. That xj had about 5.5" of lift and sits on 32s. I am old school I guess, learned to drive on a manual full size late 70's truck without abs. My first truck no abs. My first "nice almost new truck under warranty" and last had abs. I called the dealer being young and ignorant that first winter on the first snow becuase the peddle mashed to the floor made a noise and wouldn't stop. I raced quads. No proportioning valves there no emergency brakes no abs. Lock slide drift user control period. The drums are only tight and lock up first dozen or so times and thats on all new drums and hardware. You have to remember that even though they "self adjust" there still is a small procedure for it and how many of us especially those who love to complain about drums do it monthly or even yearly or even know what I am talking about. Point is either way works I go the non valve route all the time and my heaps disc around or not and adjust my driving to the brakes and machine I'm driving. For the indy car driver or nas car driver doesnt stop racing the race cause of car issues. They race until they can't or it's over. My advice is don't over think it, try it, change it later if you don't like it but it all works just mqke sure you have good ebrake cables😄.

 

Just so I'm clear on what happened with your Jeep - when you say the metering valve in your XJ was BS, does the XJ combination/proportioning valve include a metering valve for the front brake circuit (I don't know because I haven't had one apart)?  Maybe I'll take a look at one when I head to the junkyard today.  Or are you referring to the rear brake proportioning valve that is part of the XJ distribution block?  Maybe a better way to ask it is did you modify/remove the valving for the rear brake circuit in the XJ or valving associated with the front brake circuit?

 

The reason I ask is a metering valve and a proportioning valve do different things altogether and one is intended for the front brake circuit (metering valve, for front disk/rear drum applications - you would leave out the metering valve if you have all wheel disks) and one is intended for a rear brake circuit (proportioning valve).

 

I appreciate the comments about adapting your driving style to the vehicle you have, my first 4 vehicles did not have ABS and I learned to drive them just fine in snow/ice, etc...  My last and my current vehicle did/do have ABS, and if the system is working properly, those systems work rather well.  My Comanche does not have ABS and I'm fine with that, modulating the pedal is coming back to me (ABS can make you lazy).  But let's not get distracted on the topic of ABS or driving technique. 

 

I am interested in learning if there is a combination/prop valve design out there that may prevent premature locking of the rear brakes for the Comanche, so my questions above regarding what appears to be the absence of a metering valve for the front brake circuit on the Comanche specific distribution block and questions about how the Wilwood single in/single out style proportioning valve operates still stand.  

 

And yes, I do have new e-brake cables going in as part of the axle swap/lift and I'll be making sure the adjusters and wheel cylinders on the new to me rear axle are good to go.  I suppose that doing a rear disk swap at the same time isn't out of the question and may simplify the braking setup.  I have an XJ44 rear that's going into it, I managed to get one cheap at a local pick and pull.  In any case I'm hoping to grab a 95/96 dual diaphragm booster and MC today, and from what I've read - that should help overall performance of the brakes.

[Eagle]

4 hours ago, ShortBox88 said:

 

Just so I'm clear on what happened with your Jeep - when you say the metering valve in your XJ was BS, does the XJ combination/proportioning valve include a metering valve for the front brake circuit (I don't know because I haven't had one apart)?  Maybe I'll take a look at one when I head to the junkyard today.  Or are you referring to the rear brake proportioning valve that is part of the XJ distribution block?  Maybe a better way to ask it is did you modify/remove the valving for the rear brake circuit in the XJ or valving associated with the front brake circuit?

 

 

Elsewhere on this forum I also posted a photo of an XJ proportioning valve sliced in half. The portion serving the front brakes is exactly the same for the XJ and the MJ. The difference is that the XJ unit has a proportioning function for the rear wheels, the MJ unit does not. The MJ handles rear brake proportioning with the height/load sensing valve above the rear axle.

 

I also eliminated the height sensing valve in an MJ. In my '88, the height sensing valve exploded in a panic stop situation. No replacement available, so I just eliminated it. The rear brakes are a bit "touchy" under certain conditions but, most of the time, the overall braking is far better than it ever was with the height sensing valve in place. The reason, of course, is that it basically eliminates the rear brakes unless the truck is heavily loaded.

 

Found my photo of the XJ proportioning valve:

[ShortBox88]

5 hours ago, Eagle said:

Found my photo of the XJ proportioning valve:

Very interesting, neither the XJ or MJ distribution blocks use a metering valve on the front brake circuit.  When I converted my van to rear disks I had to gut the metering valve on the front brake circuit as it was no longer necessary - no need to delay the application of the front disk brakes so the rear drums could catch up since I got rid of the rear drums. I also had to gut the rear brake circuit proportioning valve in the van's distribution block, I assumed it was not really appropriate for the rear disks and I used an in-line Wilwood "proportioning" valve for the rear circuit instead.

 

Eagle - thanks for digging up that picture.  In concept, I like the idea of the load sensing valve with the redundant emergency bypass, but I'm not sure I'm a fan of how it is implemented on the MJ.  Seems like it would be pretty easy to damage it while off road.

 

I'm going to keep digging on what exactly the Wilwood single in/single out "proportioning" valve actually does as I'm now wondering if that was the right move on my van after reading what 1stDeuce stated about the function of that valve (quoted above in my original post).  I did grab a dual diaphragm booster, MC and distribution block from a '96 XJ today, but at the moment looks like replacing the water heater (just found it leaking) is my next time-sink task.

[Eagle]

I did a little playing in Paint. Here are both of them, for comparison:

 

 

[coolwind57]

I'll toss this at you, just as a different approach.  I read all I could about brake upgrades.  I went the inexpensive and simplest route and I'm quite satisfied with vastly improved braking.  Started with stock brakes--booster, master cylinder, etc.  PO had bypassed load sensing valve.  I removed all brake lines and I removed my stock proportioning valve.  Installed a single "T" to run the front brakes, so no restrictions.  Ran a single line to rear with an adjustable proportional valve (located it under the hood).  Removed all existing load sensing valve components.   I have hauled stuff just a few times, and so far I've had no need to adjust my adjustable proportional valve. 

 

Rear brakes have not been "touchy" in my experience and that's probably because there is somewhat a restriction due to the addition of the adjustable prop valve installed in line.  And again, I've not pushed the limits yet on payload.  Front brakes have no real restriction as they did before I eliminated the stock prop valve.  

 

Advantages and disadvantages on anything you do.  Folks here are passionate on their opinions and approaches.  I just thought I'd share my approach, which I credit to Cruiser54.  He had done this mod to more than one vehicle, I believe.  He explains this on this thread, first page:

On 3/11/2018 at 9:27 PM, ShortBox88 said:

https://comancheclub.com/topic/53274-mj-load-sensing-valve-delete-procedure/

 

I've got pics of what I did on here somewhere if you'd like to check it out just for giggles.  

[cruiser54]

1 hour ago, coolwind57 said:

I'll toss this at you, just as a different approach.  I read all I could about brake upgrades.  I went the inexpensive and simplest route and I'm quite satisfied with vastly improved braking.  Started with stock brakes--booster, master cylinder, etc.  PO had bypassed load sensing valve.  I removed all brake lines and I removed my stock proportioning valve.  Installed a single "T" to run the front brakes, so no restrictions.  Ran a single line to rear with an adjustable proportional valve (located it under the hood).  Removed all existing load sensing valve components.   I have hauled stuff just a few times, and so far I've had no need to adjust my adjustable proportional valve. 

 

Rear brakes have not been "touchy" in my experience and that's probably because there is somewhat a restriction due to the addition of the adjustable prop valve installed in line.  And again, I've not pushed the limits yet on payload.  Front brakes have no real restriction as they did before I eliminated the stock prop valve.  

 

Advantages and disadvantages on anything you do.  Folks here are passionate on their opinions and approaches.  I just thought I'd share my approach, which I credit to Cruiser54.  He had done this mod to more than one vehicle, I believe.  He explains this on this thread, first page:

 

I've got pics of what I did on here somewhere if you'd like to check it out just for giggles.  

Yep. Been down the same road.

 

The MJ prop valve has smaller orifices to the front brakes than the XJ. Smaller than the I.D. of the brake lines themselves. Huge difference eliminating the LSV, T the front lines and adjustable prop valve to the rear. 

[Eagle]

3 hours ago, cruiser54 said:

 

The MJ prop valve has smaller orifices to the front brakes than the XJ. Smaller than the I.D. of the brake lines themselves. Huge difference eliminating the LSV, T the front lines and adjustable prop valve to the rear. 

 

 

I noticed that working with the full-size photos of the two cut-away valve bodies. The circuit for the front brakes is straight through, with the slider in the middle. What's wrong with just drilling out the front orifice? Easy to do if you simply remove the slider. That way, you retain the brake warning function of the factory valve.

[ShortBox88]

12 hours ago, coolwind57 said:

Started with stock brakes--booster, master cylinder, etc.  PO had bypassed load sensing valve.  I removed all brake lines and I removed my stock proportioning valve.  Installed a single "T" to run the front brakes, so no restrictions.  Ran a single line to rear with an adjustable proportional valve (located it under the hood).  Removed all existing load sensing valve components.

So, if I'm following, you ran a single hard line from the front brake feed on the MC to a convenient point to transition to a flex line down to the front axle where you have a Tee installed and hardline to each side of the axle (somewhere around the inner C on each side) then a flex line to each caliper?  Kind of like older Dodge pickups?

 

Or did you keep hard line to each "frame rail" up front at the stock location and put the Tee near the MC and then individual flex lines to the caliper from the frame?  Seems like you're giving up the brake warning light and the ability of the stock distribution block to isolate the front or rear brake circuit if either one should develop a leak or fail in a panic stop situation, correct?

 

For the rear brake circuit, I'm likely to do the same as you did, I just want to confirm exactly how the Wilwood or similar single in/single outlet adjustable proportioning valve works first.  That is essentially what I did with my van, but I'm wondering if the adjustable prop valve simply holds a constant pressure once you hit the manually adjusted limit and never exceeds that pressure no matter what the input pressure is or if the outlet pressure will still increase (providing the input pressure continues to increase) but at a lesser rate?  I sent Summit a tech question on this, usually they are pretty good about getting back on that kind of stuff.  May not hurt to contact Wilwood directly either... 

 

11 hours ago, cruiser54 said:

The MJ prop valve has smaller orifices to the front brakes than the XJ. Smaller than the I.D. of the brake lines themselves. Huge difference eliminating the LSV, T the front lines and adjustable prop valve to the rear.

  So maybe the ticket is keep the XJ prop valve I have and swap the ZJ rear valving in when I do convert to rear disks, or just gut the XJ rear valving and use the adjustable in-line prop valve, Cruiser - do you have an opinion on which performs better?

 

I also just noticed something in this thread, while re-reading it:

https://comancheclub.com/topic/53274-mj-load-sensing-valve-delete-procedure/?page=4

 

"For your 92MJ, the 95/96 booster master is pure bolt-in. The only fab you have to do are the two brake lines from your existing distribution block to the new master cylinder. Buy a 2' length for pre-flared 3/16" brake line from AZ or similar, use the two existing flares on the distribution block, bend and flare the other ends for the master, and bolt it in. Easy-peasy and an excellent brake upgrade.

 

"

Clearly that's not the stock washer bottle, while looking under the hood today - to get that XJ booster to fit what am I into?  I still have the stock bottle and airbox.  Looks like it may be tight...

 

 

   

[ShortBox88]

8 hours ago, Eagle said:

 

I noticed that working with the full-size photos of the two cut-away valve bodies. The circuit for the front brakes is straight through, with the slider in the middle. What's wrong with just drilling out the front orifice? Easy to do if you simply remove the slider. That way, you retain the brake warning function of the factory valve.

I don't see why that wouldn't work.  Would you also need to drill out the hex fitting labeled RF line in this picture as well? (I know it's not an MJ valve, but same arrangement on the MJ valve, I think)

 

 

[Eagle]

1 hour ago, ShortBox88 said:

I don't see why that wouldn't work.  Would you also need to drill out the hex fitting labeled RF line in this picture as well? (I know it's not an MJ valve, but same arrangement on the MJ valve, I think)

 

 

Yes, I guess you would. I forgot about that, to be honest.

[coolwind57]

1 hour ago, ShortBox88 said:

So, if I'm following, you ran a single hard line from the front brake feed on the MC to a convenient point to transition to a flex line down to the front axle where you have a Tee installed and hardline to each side of the axle (somewhere around the inner C on each side) then a flex line to each caliper?  Kind of like older Dodge pickups?

 

Or did you keep hard line to each "frame rail" up front at the stock location and put the Tee near the MC and then individual flex lines to the caliper from the frame?  Seems like you're giving up the brake warning light and the ability of the stock distribution block to isolate the front or rear brake circuit if either one should develop a leak or fail in a panic stop situation, correct?

 

For the rear brake circuit, I'm likely to do the same as you did, I just want to confirm exactly how the Wilwood or similar single in/single outlet adjustable proportioning valve works first.  That is essentially what I did with my van, but I'm wondering if the adjustable prop valve simply holds a constant pressure once you hit the manually adjusted limit and never exceeds that pressure no matter what the input pressure is or if the outlet pressure will still increase (providing the input pressure continues to increase) but at a lesser rate?  I sent Summit a tech question on this, usually they are pretty good about getting back on that kind of stuff.  May not hurt to contact Wilwood directly either... 

I'll answer/clarify some of your questions at the bottom of my response but I thought I'd share my original write-up first.  I've cut and pasted applicable and usable parts and comments here:

 

  

"MY SITUATION:  Original front disc and rear drums.  Height Sensing Valve (HSV) half-assed deleted by PO.  Still had 2 old crappy brakes lines running to rear.  Acceptable brakes as a whole, but redoing it all because I already have the truck apart anyway and didn't like the rusty, brittle looks of things.  Plan is to renovate brake system for added reliability and maybe even get some added performance as a bonus.    

 

I chose to start things off by trying Cruiser54's front Proportional Valve (PV) trash and replace procedure.  This seemed logical as a way of simplifying things and perhaps improving front brake performance..  Plus He's got real-world experience doing this and it has worked for him multiple times. 

 

I figured at least to me, that the MJ PV was designed to work a system that included the additional second brake line to the rear (to be used in cases of front brake failure) AND a system including a well-working HSV.  Since I now have neither, the MJ PV is no longer being used exactly according to its design with those two aspects missing.   

 

The MJ PV meters the front brakes down considerably after the brake line run into it from the master cylinder.  Just look up some of Cruiser54's pictures of those tiny little orifices in there.  Remove entire PV and then T-off to your front calipers, using an inverted flare brass T.  You should get better braking because the small orifices of the prop valve to the front brakes are eliminated.  You're now running near-full opening size of the hard brake lines that are coming off direct from the master cylinder.  Makes sense to me so I did it:

 

and here's a view from side/bottomp:

 

Now technically I should experience slightly better front brake because I have larger interior diameters running from the master cylinder on through to the calipers.  

 

Because I am eliminating some front and rear "bottle-necking" I used to have at the now-removed PV, I agree with many others here that an Adjustable Proportioning Valve  (APV) may be a good idea FOR THE REAR BRAKES.  This should eliminate any rear brake lockup that I may experience if I am running a heavy payload.   The original intent of this thread was to see where other guys were mounting their APVs.  I ended up deciding on mounting mine under the hood after all.  Even though TJ1 had a cool location on his rig, I ultimately sided with HOrnbrod's opinion of not having brake lines inside my cab.  Mounting near the rear of the bed would likely affect longevity and stable function due to full exposure to elements.  

 

I  completely eliminated my two old hard rear brake lines and ran a new single line back there the the axle.  So here's where I ended up mounting my APV:

 

I chose the Speedway APV because it is compact and appears to be simple and tough.  Another cool feature is that it allows for full shut down of fluid to the rears, which can possibly come in handy when working on your brakes.  

 

REMINDER:  If you've read much on the topic of HSV deleting/PV deleting/running a single line to your rears, keep in mind that you'll lose that safety feature that allows full braking to the rears in cases of front brake failure.  

 

Speedway didn't have comprehensive flow specs on that mini APV that I show in the picture.  it shows gpm and max psi and states that it can be completely shut down whatever line it is controlling if desired.  I was curious of flow characteristics during "fully open" setting.  

 

FYI for the benefit of anyone interested in this particular device, I sent them a message and here's their response:

 

Perry, I just spoke with one of my techs and he stated that it will not be fully open when the valve is fully open, there will still be some restriction there.

 

Thinking around 20% restriction, so it'll flow 80% of the fluid that a straight line will.

 

As far as I know, we do not offer a proportioning valve that will flow as if there is nothing there while fully open, however the purple proportioning valve might flow a little better as it is not a complete shutoff valve while fully closed, there will likely still be a bit of resistance there.

 

https://www.speedwaymotors.com/Speedway-Purple-Adjustable-Brake-Proportioning-Valve,23498.html

 

 

My brakes ROCK now!  Got my MJ running last night and took her for a spin.  My brakes were not so bad to begin with.  But now they are excellent!  Feels like I have 4-wheel disc brakes. 

 

Many thanks to Cruiser54 for the advice on ridding the front proportional block.  I have killer good brakes, and I now have the ability to adjust the rears (or shut them down if I choose to)""

 

 

Ok, that's pretty-much the write up.  Here's to clarifying and answering some of your questions:

1.  It looks like I may had used the factory lines that I now have coming from my added "T" running to each of the front brake calipers.  I think I simply screwed the 30+ year old brake line threads into a new inverted flare "T".  BTW, It took some active shopping around to find the correct sized fittings/adapters to use stock flare fittings and MC orifices with new....I didn't want to have to cut double flares on new and factory brake lines, so I had to use my brain a bit during shopping to avoid cutting/flaring.

 

2.  By design, I certainty now have isolation of from and rear brakes, for sure!  Front and rear have two different and very separate paths.  They obviously already have two different reservoirs inside your master cylinder.  My system continues from there to NOT cross paths with each other.  As I had mentioned in my original comment on this thread above, there are advantages and disadvantages to nearly anything you do.  I'm pushing full volume to my front brake calipers now instead of dealing with a factory bottle neck.  Overall, front-and-back, I can say that I've got superior braking ability compared to what I originally had.  And at great cost and time savings.  Disadvantage is that I may lose some "fail-safe" capabilities, if you will.  I weighed perceived consequences, and then decided on my course of action.  This method works for me, no regrets.  

 

3.  If I lose my front brakes, I still have rear brakes, although the addition of the aftermarket adjustable prop valve doesn't give me full 100% use of the brake line ID.  I do not know to what degree my rear brakes assist my stopping if I suddenly lose my front.  In my 35+ years of driving, I don't recall ever running into the loss of brakes of either end, so I'm not too worried.  I also do have my emergency brake as a back up.   Of course, nearly any valve installed on a brake line will add some restriction.  I can also shut down my rear brakes totally if I want to.  If you like to show off and do burn-outs, then this is a nice feature!  This isn't me, but I give it as an example.  Shutting down rears is also nice if you're working on your rear brakes and want to shut off fluid completely.  

 

Weigh your decision.  Many ways to skin a cat.  Again, Cruiser54 has done front prop valve deletes on multiple vehicles.  You can now add me to the list who's done it and is happy with it.  

[HOrnbrod]

2 hours ago, ShortBox88 said:

I also just noticed something in this thread, while re-reading it:

https://comancheclub.com/topic/53274-mj-load-sensing-valve-delete-procedure/?page=4

 

"For your 92MJ, the 95/96 booster master is pure bolt-in. The only fab you have to do are the two brake lines from your existing distribution block to the new master cylinder. Buy a 2' length for pre-flared 3/16" brake line from AZ or similar, use the two existing flares on the distribution block, bend and flare the other ends for the master, and bolt it in. Easy-peasy and an excellent brake upgrade.

 

"

Clearly that's not the stock washer bottle, while looking under the hood today - to get that XJ booster to fit what am I into?  I still have the stock bottle and airbox.  Looks like it may be tight...  

 

Clearly it's not. It's a 97+ washer reservoir inside the fender. Makes for lots of room..

 

https://comancheclub.com/topic/5536-new-windshield-washer-tank-installed/

 

 

 

[HOrnbrod]

9 minutes ago, saveevryjp1998 said:

It will still work that booster set up. I bet hundreds have done it including myself maybe thousands.

 

Maybe millions.

[ShortBox88]

On 3/13/2018 at 9:32 PM, HOrnbrod said:

Clearly it's not. It's a 97+ washer reservoir inside the fender. Makes for lots of room..

 

https://comancheclub.com/topic/5536-new-windshield-washer-tank-installed/

I like this mod, I'll have to dig up the later bottle and pumps to free up engine bay space.  With the XJ booster installed and stock air box the original washer bottle did get moved about an inch forward and it just touches the stock airbox and the booster.  I had to trim the stock airbox lid slightly to free up space.

 

On 3/13/2018 at 9:13 PM, coolwind57 said:

REMINDER:  If you've read much on the topic of HSV deleting/PV deleting/running a single line to your rears, keep in mind that you'll lose that safety feature that allows full braking to the rears in cases of front brake failure.  

Yep, that is one thing I did like about the OEM setup, the redundant line for full pressure braking to the rear if you lose the front.  However, I've been thinking about whether that would give you better control of the vehicle in a situation where you've lost the front brakes and are rear brake only?  Not sure...???

 

Here is a list of what I did do since my last response on this post (apologies if some of this wanders off track):

 

Found and pulled a 3.73 D30 front housing from an '85 Cherokee and a 3.73 Explorer 8.8 LS disk brake complete rear axle from a '96 Explorer at a local pick and pull.  Decided that I will likely sell the XJ D44 3.55 LS rear and matching front D30 axle I originally intended to use.  

 

New upper and lower ball joints on the D30.  Added a CJ D30 1310 u bolt yoke for the driveshaft connection and new pinion seal to the 3.73 D30 along with new upper control arm bushings.  Put my original D30 knuckles, brakes, unit bearings, etc... on the new to me 3.73 D30 front.  I had already converted my original CAD dana 30 to a 1-piece axle shaft setup w/297s so re-used those axle shafts in the 3.73 housing.  Added new early 90's GM truck flex lines to the calipers and relocated the hard line on the frame on each side to accommodate future lift.

 

On the 8.8 had to put in new parking brake parts (they were shot) and wheel seals on each side.  Calipers, rotors and brake pads all looked to be in good shape so I used them.  Used 2 long side (passenger) Explorer parking brake cables, one is a little sticky so it may get replaced next time I head to the u-pull.  I also pulled some extra steels and friction plates from another LS 8.8 to help the original LS clutch packs that were pretty beat.  Grabbed a 1310 companion flange from a 2WD Ford Ranger with an 8.8 rear to mate up to the stock driveshaft.  Cut the spring perches off and moved them out to match the MJ leaf spring spacing, set the pinion angle under the truck and welded them on.  Added a new 96 Dodge Dakota rear brake flex line to accommodate future lift.  Had to replace the hard lines on the axle as I used a second 8.8 passenger side flex line to the caliper on the drivers side caliper.  The original 8.8 drivers side flex line to the caliper is integrated into the tee fitting and flex line that goes up to the frame, I didn't want to re-use this so the Dakota flex line was put in it's place and a short hard line was installed to run to the drivers side caliper + the second passenger side flex line installed on that side.  Put on some slightly taller XJ lift shackles that I had pulled from the same 96 XJ I got the booster/prop valve/MC from.  All in all with the stock springs, slightly taller shackles and SUA with the larger 8.8 axle tubes I lost about 3/16" height in the rear...

 

Note - the stock driveshaft is too long, I knew it was tight but I decided to test drive it anyway - pushed the rear output bearing into the transfer case and broke out the shoulder the bearing rests against out of the tailhousing.  The bearing was still in the bore where it should be, but just pushed in enough to break the shoulder.  I've been having aluminum in t-case oil issue for a while now and after the test drive I had planned to swap the oil pump and clean out the t-case thinking that maybe my oil pump was the issue, I've looked almost everything else and can't seem to figure out where the aluminum is coming from...  It's not the chain, clearanced the alum shift fork where it was showing some wear, etc...  As I took the case apart I found the break in the tail housing...  If I had not been planning a pump replacement I may have never know that the damage had occurred. 

 

At this point I'm over it and done with this t-case, it's been apart too many times and I'm tired of trying to sort it out - so I'm just trying to get it to function a while longer.  I know it's kind of a BS fix but I have a Strongbox/EB Dana 20 that I'm waiting on a few parts to finish, plus a lift going in soon so I decided to make it work with the driveshaft I have for the time being, so the slip yoke on the driveshaft got trimmed about 1/2" and the bearing was re-installed with some bearing and sleeve retainer using the extension housing to place the bearing...  The lift is the next step, so at that time I *may* decide to replace the driveshaft slip yoke and t-case tailhousing until I get the Dana 20 finished and some driveshafts built to fit the lift and t-case transplant correctly.  I just didn't feel like spending the money to get the driveshaft shortened only to replace it entirely in a few months...  Seems to be working right now, I guess the only way I'd really know is to drive it some more and pull the case apart again to see if the rear bearing moved in the tailhousing (not likely unless I have to).  Or the bearing will just walk into the speedo drive gear and the case will start making nasty noises... 

 

I thought it was worth mentioning that the stock driveshaft was too long on an 8.8 swap at stock height/springs (mine is a Pioneer with the D35).  Not sure if this would be true for all short box MJ's with Dana 35s or not...  Another way around it would have been to use aftermarket spring plates that let you move the rear axle back or possibly a junkyard rear driveshaft form a Dana44 manual or Dana35 automatic shortbox MJ from what I read, but I was re-using the 8.8 perches and my existing driveshaft for now for now.

 

I removed the LSV and simplified things down to a single line to the rear brakes.  I considered keeping the redundant emergency line but rounded off the brake line fitting when trying to get it apart, I think it had pretty much rusted itself to the line...  decided to just remove it...  I re-bent and re-flared the primary hard line from the dist block to mate up with the Dakota flex line at the frame side.  I had cut the Explorer frame side mounting flange off with the original flex line on the 8.8 so I trimmed and welded the Explorer frame side flex mounting flange to the MJ frame side flex mounting flange and the Dakota flex line went right into the modified Explorer/MJ flex line frame side mounting flange with a little filing on the flange.

 

Put in the 96 XJ booster, MC and prop valve - however, I pulled disk brake ZJ prop valve guts and swapped those into the XJ prop valve/distribution block to get hopefully better performance out of the new to me rear disks. Interestingly, the XJ booster, MC and prop valve/dist block I pulled were from an ABS truck.  I want to say that side by side with the MJ distribution block the orifices in each of the brake line ports visually appeared to be identical in size, I was in a hurry having borrowed shop space to do the swap and didn't measure the diameters in the brake line ports, but it was definitely smaller than the ID of the 3/16" brake line.  From the pictures above what I assume is a non-ABS XJ dist block clearly has larger ports.  That and there is only one feed for the front brake lines on the ABS XJ distribution block, which goes to the ABS unit that then splits them to each side.  Where you would normally have a second port for the front brake lines, labelled RF below the ABS XJ dist block had a plug.  I replaced this plug with the RF fitting from the MJ dist block to get two ports on the ABS XJ dist block

On 3/13/2018 at 7:04 PM, ShortBox88 said:

 

 

Just a note - not my picture, just using it in this post to illustrate... 

 

So probably not the best way to do it but the brakes DO work better than the original setup.  I question whether my rear drums on the 35 were working at all...  I still have to stand on it a bit to get wheels to lock up with 30" tires.  I did bleed the system pretty thoroughly.  I would have liked to have taken the swap a little more slowly but was borrowing shop space and had limited time to tinker with the brake setup, so worked with what I had.  I'll likely have another opportunity to mess with the brake system in the next couple of months so I may either track down a non-ABS XJ dist block to swap in or maybe do something like what coolwind57 did above with and adjustable prop valve and maybe improve this further. 

 

On 3/13/2018 at 9:13 PM, coolwind57 said:

FYI for the benefit of anyone interested in this particular device, I sent them a message and here's their response:

 

Perry, I just spoke with one of my techs and he stated that it will not be fully open when the valve is fully open, there will still be some restriction there.

 

Thinking around 20% restriction, so it'll flow 80% of the fluid that a straight line will.

 

As far as I know, we do not offer a proportioning valve that will flow as if there is nothing there while fully open, however the purple proportioning valve might flow a little better as it is not a complete shutoff valve while fully closed, there will likely still be a bit of resistance there.

 

https://www.speedwaymotors.com/Speedway-Purple-Adjustable-Brake-Proportioning-Valve,23498.html

 

Here is what Wilwood said about the single inlet/single outlet adjustable prop valve they sell:

"

Hi Mark,

 

Thank you for the inquiry with Wilwood Disc Brakes.

 

In general, the output pressure/input pressure ratio will remain consistent. I.e. if you have the valve adjusted all the way and input 1000 PSI, it will output 430 PSI (max 57% pressure reduction). Now, we don’t recommend exceeding the PSI limit of the valve as it may not regulate pressure correctly beyond that point.

 

Regards,
Wilwood Disc Brakes

"

So it just provides a constant pressure reduction such that you get a % of the input pressure coming out of the valve, I'll have to check out the speedway unit, I'm guessing it likely does the same thing but did not think to ask about if there is any pressure reduction when the valve is fully open.

 

Thanks everybody for contributing the knowledge and experience with the braking systems.  It helped me quite a bit!