Rear Proportioning Valve Comments

[HOrnbrod]

Been reading posts regarding bypassing the MJ rear axle prop valve (load/height sensing valve, whatever you want to call it). Most guys disable this thing because it doesn't work and you can't get them anymore. But it appears mine still works. Last weekend I installed a pair of metric ton springs that resulted in about a 2" rear lift. I also have Ford Explorer disks on the back, and had great brakes. I had to make a panic stop yesterday, and the rears locked up first immediately, which had not happened before adding the new rear springs. Figured it had to be the extra 2" (duh), so I removed the link between the prop valve and the axle, and fabbed a new rod 2" longer so the prop valve still thinks the bed is unloaded. The brakes now work as before with the fronts locking up before the rears. So I'll stick w. what I got, until the valve craps out.

[Oizarod115]

my connector rod fell off at some point and my junk stops... slowly, but it stops.

[Kenosha Warrior]

my connector rod fell off at some point and my junk stops... slowly, but it stops.

 

I yanked the master yesterday, swapped in a new one, and got decent brakes for once. I have new lines front'ta'back but that prop valve is still there, my rears lock like nothin though. My arm is siezed on nice and tight too. Oh well. love my mj.

[Eagle]

Been reading posts regarding bypassing the MJ rear axle prop valve (load/height sensing valve, whatever you want to call it). Most guys disable this thing because it doesn't work and you can't get them anymore. But it appears mine still works. Last weekend I installed a pair of metric ton springs that resulted in about a 2" rear lift. I also have Ford Explorer disks on the back, and had great brakes. I had to make a panic stop yesterday, and the rears locked up first immediately, which had not happened before adding the new rear springs. Figured it had to be the extra 2" (duh), so I removed the link between the prop valve and the axle, and fabbed a new rod 2" longer so the prop valve still thinks the bed is unloaded. The brakes now work as before with the fronts locking up before the rears. So I'll stick w. what I got, until the valve craps out.

More lift would be like running with less load and should result in LESS braking to the rear, not more. Your system is messed up.

[HOrnbrod]

Eagle, respect your knowledge very much. Here's my thinking on this, just hear me out:

 

With an unlifted/unloaded MJ, say the prop valve arm is parallel with the axel. When the distance between the prop valve and axle is increased 2", the prop valve arm will be pulled down to an angle less than parallel to the axle. So by increasing the length of the rod between the prop valve arm and the axel, the prop valve arm angle is restored to parallel with the axle, right? So even though the body is lifted 2", the prop valve will bias the front/rear brakes exactly as it did previously w/o any lift. Or is my logic AFU here??

[Pete M]

The arm should be parallel at rest, yes. I'm not sure what the prop valves does when the arm moves down (due to the lift). As far as I can tell, it was really only designed to increase pressure when the arm moves up (due to a load in the bed).

[Bounty Hunter]

HB, your reasoning that lengthening the rod 2" would fix it is correct, restores things to normal. However moving the axle further from the bed should create less brake bias to the rear, causing the fronts to lock up first, as Eagle stated. Don't know why it worked the opposite for you.

[HOrnbrod]

I don't know why either. It is working correctly and as before by lengthening the rod 2", so I'll leave well enough alone. In looking in my MJ parts manual, the only consistent item on the prop valve assembly was the valve itself. The rod, arm, and bracket carried different part numbers for some years and for 2WD vs. 4WD because the 4WD stock height was taller than 2WD. Even the adjustment procedure changed between years. Maybe some individual parts have been replaced by the PO. Thanks all for the comments.

[jaekl]

I'm a bit late, but I can shed some light on the matter why the brakes locked after the lift. I had my valve apart this weekend. Inside is a cam and a cam follower. It is possible that the cam had rotated enough to be on the back side of the lobe and allowed more pressure to the rear brakes.

[HOrnbrod]

I'm a bit late, but I can shed some light on the matter why the brakes locked after the lift. I had my valve apart this weekend. Inside is a cam and a cam follower. It is possible that the cam had rotated enough to be on the back side of the lobe and allowed more pressure to the rear brakes.

 

Could be, but since I extended the activation rod exactly the same as the lift, it should be working the same as it did pre-lift. However, since I did that I have added 31" tires, and the rear seems to be braking better than before w. the 225/75/15 tires. Nice to know what's inside the leveling valve though - never had one opened up.

[HellCreek]

Hi, hornbrod,

 

You mentioned that the activation rod on the rear proportioning valve is different on 2WDs and 4WDs and also different on different years. Do you happen to know the lengths of the different rods and their applications? We are making a lift kit for the Comanches, and that information would be very helpful.

 

We have a 2WD, 1989 Sport Truck that we tested our 3 inch and 4-1/2 inch kits on, and we just made longer rods for ours.

 

Thanks,

Tom Laher

Hell Creek Suspensions, Inc.

[HOrnbrod]

Hi, hornbrod,

You mentioned that the activation rod on the rear proportioning valve is different on 2WDs and 4WDs and also different on different years. Do you happen to know the lengths of the different rods and their applications? We are making a lift kit for the Comanches, and that information would be very helpful.

We have a 2WD, 1989 Sport Truck that we tested our 3 inch and 4-1/2 inch kits on, and we just made longer rods for ours.

 

Thanks,

Tom Laher

Hell Creek Suspensions, Inc.

 

I'm just going by what it says in my 1991 FSM. There is a very detailed adjustment procedure for the 90-92 models, but right off the bat it states "DO NOT USE THIS PROCEDURE FOR MODELS BUILT PRIOR TO 1990". Since I have had only 91 MJ models, I don't know what the earlier year's adjustment procedure is. Basically for the 90-92 models, the arm is press fitted on the valve shaft by aligning alignment flats, then is rotated to a certain degree point using a factory gauge. However, in all MJ models I've seen, the arm is positioned slightly above parallel to the axle shaft (about 25 degrees). If you have lifted the vehicle, of course the arm will be pulled down, so what I did was fab a longer shaft to place the arm at about 25 degrees above parallel to the axle where it was before the lift. 1/4" solid rod may be used bent to the same contours as the old rod. You have to file a slot on each end of the new longer rod then transfer the ball socket end pieces. Maybe someone can chime in on the adj. procedure for the 89 and below models. If if the arm has never been removed from the load leveling valve, I'd just fab the longer rod to match the lift then do a smoke test with the brakes.

[HellCreek]

Hi,

 

What we did was make the shaft 3 inches longer than stock for the 3 inch lift and 4-1/2 inches longer for the 4-1/2 inch lift, but, as I mentioned, we have a 2WD Comanche. You indicated that the 4WDs had different length rods, and we were wondering what those differences are.

 

Thanks,

Tom

[Pete M]

4wd Comanches are about 1" taller than 2wd Comanches so I'm guessing that the 4wd connecting rods are about an inch longer.

[HOrnbrod]

Hi,

 

What we did was make the shaft 3 inches longer than stock for the 3 inch lift and 4-1/2 inches longer for the 4-1/2 inch lift, but, as I mentioned, we have a 2WD Comanche. You indicated that the 4WDs had different length rods, and we were wondering what those differences are.

 

Thanks,

Tom

 

I did the same for my 91 2WD w. 2-1/2" lift and all is well. And Pete's exactly right; the 4WD does set 1" higher than the 2WD from the factory, so the rod is 1" longer.

[HOrnbrod]

Hi,

 

What we did was make the shaft 3 inches longer than stock for the 3 inch lift and 4-1/2 inches longer for the 4-1/2 inch lift, but, as I mentioned, we have a 2WD Comanche. You indicated that the 4WDs had different length rods, and we were wondering what those differences are.

 

Thanks,

Tom

 

I did the same for my 91 2WD w. 2-1/2" lift and all is well. And Pete's exactly right; the 4WD does set 1" higher than the 2WD from the factory, so the rod is 1" longer.

 

BTW Tom, are you supplying shocks with your lift kits? Fronts are easy, same as for the XJ's. The stock MJ rear shocks do not have enough travel for 2-1/2" lifts and higher, so I ended up using OME ZJ shocks - had to press the bar pins out.

[HellCreek]

Hi,

 

Yes, we are supplying longer shocks for the front and rear. Essentially, the front is the same as a XJ Cherokee lift. As you know, the rear requires longer springs designed to go under the axle. We have developed those using our MJ as a pattern. Our Avitar is our Comanche with the 4-1/2 inch kit installed.

 

Thanks,

Tom

[JeepcoMJ]

hellcreek, is that the lift with the OME front shocks and the bolt-on SOA rear lift system?

 

Not to insult, but I certainly hope not, that lift is one of the most chintzy lift's I've ever seen and puts OME to shame.

[Oizarod115]

hellcreek, is that the lift with the OME front shocks and the bolt-on SOA rear lift system?

 

Not to insult, but I certainly hope not, that lift is one of the most chintzy lift's I've ever seen and puts OME to shame.

 

hellcreek is his company, i think they MADE that kit. :cheers: sounds like they're having rear SUA lift springs done up? correct?

[HOrnbrod]

hellcreek, is that the lift with the OME front shocks and the bolt-on SOA rear lift system?

 

Not to insult, but I certainly hope not, that lift is one of the most chintzy lift's I've ever seen and puts OME to shame.

 

Don't think so. Here's their web site:

 

http://www.hellcreeksuspensions.com/

[JeepcoMJ]

good, then hellcreek, welcome to the club. your suspensions are good so I must be kind :D

[HellCreek]

Hi,

 

This is not an OME kit or anything like it. Our kit is made up of Heckethorn (Rough Country) parts for the front and our own manufactured leaf springs for the rear (they go under the axle as Jeep intended). We also use Rough Country shocks. You will not find this kit on our website, since it is brand new and not quite ready for production. The prototype kit is on our MJ.

 

Thanks,

Tom

[JeepcoMJ]

Hi,

 

This is not an OME kit or anything like it. Our kit is made up of Heckethorn (Rough Country) parts for the front and our own manufactured leaf springs for the rear (they go under the axle as Jeep intended). We also use Rough Country shocks. You will not find this kit on our website, since it is brand new and not quite ready for production. The prototype kit is on our MJ.

 

Thanks,

Tom

 

Tom, I appreciate your stating what it is. i know i sounded like an @$$, but when i saw the lift that I had in mind, i was so thoroughly disgusted. i even saw one ON an mj in town and it was so freaking shoddy and just terrible.

 

i like your lift, let me know when production comes around, as I'm gonna need a couple lift kits :D

[HOrnbrod]

Hi,

 

This is not an OME kit or anything like it. Our kit is made up of Heckethorn (Rough Country) parts for the front and our own manufactured leaf springs for the rear (they go under the axle as Jeep intended). We also use Rough Country shocks. You will not find this kit on our website, since it is brand new and not quite ready for production. The prototype kit is on our MJ.

 

Thanks,

Tom

 

Well Tom, when you asked about adapting the MJ-unique rear load leveling valve when developing your kit, it was obvious you were thinking details for our rigs, not just lumping them into another crappy AAL XJ-type lift kit. I can not speak for the club, but please keep us informed of recent developments, and we'll assist in any way. Good bunch on this forum. Don

[HellCreek]

Hi, JeepcoMJ,

 

Not to worry - been there, done that. I will let you know when these are ready.

 

Hi, Don,

 

Actually my first contact with a rear brake proportioning valve was on a Chevy 1 Ton that I owned. It seemed like a great idea to me - the more weight you put in the bed, the better the brakes. It still seems like a good idea - if it works properly.

 

Yeah, I hate AALs as well. It's not so much the AAL itself, which is the cheapest way to lift a vehicle when you can't use blocks, it's just that, if the rest of the spring is weak, the lift is doomed to failure. The same can be said of SOA, unless you buy new springs or already have a set of good ones.

 

I will keep y'all informed (Mississippi for you guys), and I appreciate any help that anyone can give me.

 

Thanks,

Tom