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Adjustable MJ Load Sensing Valve

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I know a lot of y'all have junked the rear load sensing valve - I haven't since mine still is doing it's job. If your existing rod from the valve arm to the diff cover is gone or is toast, here's how to make a new one that's adjustable. This is similar to how Toyota does it on their trucks. Also, if you have lifted your rig, the rod must be lengthened by the same amount as the lift to regulate the rear brake bias properly. I made a new non-adjustable one when I did my lift, but I didn't like it and wanted to fine tune the rear brake bias if I needed to. Parts needed for the adjustable rod are two aluminum 1/4"x28 LH spherical threaded rod ends w. studs, a length of stainless 1/4"x28 LH threaded rod, and four 1/4"x28 stainless nuts, washers, and lock washers. I got all the stuff at my local Ace hardware for about $15.

First pop off the old rod and unscrew the ball-end fittings from the diff cover bracket and valve arm:

R1rdR4o.jpg

Old rod and ball ends:

xoL7D2a.jpg

Assemble the new hardware. I cut the threaded rod off (about 7" long) so that the arm was parallel with the axle when the threaded rod was screwed into the spherical rod ends all the way. This allows about 1-1/2" of adjustment out of the ends to increase the length of the rod and adjust the rear brake bias if necessary:

3tpB7uN.jpg

Fully installed:

AeHtufU.jpg

Optional: After you get the rod adjusted correctly, cover the threads with a piece of stainless steel tubing for protection. Looks prettier too. biggrin.png

9bHIHt7.jpg

Now go find a wet parking lot and do some smoke tests to see how the front and rear brakes lock up and adjust to your preference. :cheers:

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:bowdown: I will be doing this very soon for sure, or you can just give me your truck so io don't have to worry about making one myself.... :brows: nice work! :thumbsup:

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Very nice. I did not know Ace had all that. Hmmm, I've been wanting to make some swaybar end links..

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Very nice. I did not know Ace had all that. Hmmm, I've been wanting to make some swaybar end links..


My local Ace didn't have the rod ends, but the bigger Ace in the next town did.

Follow up: We had a some rain yesterday, and I brought the old girl to a nearby abandoned parking lot and played with the bias adjustment. With no load the fronts lock up just before the rears. I adjusted it longer about 1/4", and the rears lock up with the fronts, and the braking feels better. I had no idea the arm position height was so sensitive, but it works as expected.

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Do all Comanche's have this? There's nothing that even looks like that under mine. But my rears lock up way before my fronts do. Could I get one from the parts store or JY off a Cherokee?

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Cherokees never had them and the Comanche valve is not available anymore through any known company. But you can get an aftermarket adjustable proportioning valve from places like Summit Racing. It won't be load sensing, but it'll allow you to tweak the pressure to get it right. :thumbsup:

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Do all Comanche's have this? There's nothing that even looks like that under mine. But my rears lock up way before my fronts do. Could I get one from the parts store or JY off a Cherokee?

 

Your original valve has probably been bypassed and discarded then. Look under there and see if you have two brake lines running from the combo valve under the master cylinder to the rear axel. If it's been bypassed one of the lines will be abandoned (or removed).

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Do all Comanche's have this? There's nothing that even looks like that under mine. But my rears lock up way before my fronts do. Could I get one from the parts store or JY off a Cherokee?

 

Your original valve has probably been bypassed and discarded then. Look under there and see if you have two brake lines running from the combo valve under the master cylinder to the rear axle. If it's been bypassed one of the lines will be abandoned (or removed).

 

Or the 2 may be tied together somewhere with a T fitting. :thumbsup:

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Found one today. My friend just happend to have it sitting around. Don't know if it works or not. Brake line was kinked going to my old one right at the end. Hopefully I'll have it on tomorrow. Have everything but the hardware this replaces lol.

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Anyone have a diagram showing the stock brake line routing? I found the "load sensing valve eliminating" diagram in the common useful pics thread but cannot find one that includes the stock valve, which I want to keep.

 

Great writeup! My link bar between the valve and the diff is gone so I will be using this to make myself a new one.

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Pretty close, thanks a lot! The only thing I'm confused about now is the stuff at the rear (looking at MrSimon's first pic - the stock setup.) From the look of it there's a separate block with 4 ports and a load sensing valve back there, but on mine I just have a load sensing valve with 3 ports - two for the brake lines to the front, one going to the rubber brake line for the rear axle. What I'm really worried about is whether the two lines to the front have been swapped, because the brake lines were all replaced (I guess you could call it that) by either the previous owner or his extremely cheap, lazy mechanic. Whoever did it did a terrible job and I have very little faith in them getting the lines routed properly.

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Got a couple actually... had a chance to get under the MJ with a camera last night. It's worse than I remembered - note the T-junction and compression splice, along with the old rusted out line being used as a support for the new line!

 

The T-junction and compression splice:

pict0072j.th.jpg

 

Everything:

pict0071j.th.jpg

 

Another shot:

pict0070cc.th.jpg

 

From what I can tell, one line from the front goes to the top of the load sensing valve AND directly to the rear axle (via the T splice) while the other line goes to the side port on the load sensing valve via the compression splice. I'm not sure which line is which going to the front (and as you can tell from the quality of work here, I don't think I should trust that it's correct) but I can trace that easily... just not sure what the proper routing is due to the 4-port mystery box on the rear axle shown by MrSimon's diagram. Maybe my routing is correct (except possibly lines to the front swapped) and the 4-port box is actually the combination of the T-junction and the rear brake hose, which has 2 ports on the axle end?

 

Also... just did the WJ master cylinder + booster swap last night. All I can say is that it's GREAT! Even with my rear brakes nearly inoperative, I can stop much faster than I could before.

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I vote a mixed greens salad, balsamic vinagrette, and a nice bottle of Chianti to go with that plate of spaghetti you got there Kas.

 

Jeff

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I vote a mixed greens salad, balsamic vinagrette, and a nice bottle of Chianti to go with that plate of spaghetti you got there Kas.

 

Jeff

 

 

MJeff........Your confusing the 'ole Chef years with the Wrenching years again :shake:

 

 

kastein - Do your self a favor, and tear all that junk out of there, and get rid of the load sensing valve, and read the post on running ONE hard line to the rear.

 

The less lines and connections, twists and turns you have, the better chance you'll have less problems latter on.

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I vote a mixed greens salad, balsamic vinagrette, and a nice bottle of Chianti to go with that plate of spaghetti you got there Kas.

 

Jeff

 

 

MJeff........Your confusing the 'ole Chef years with the Wrenching years again :shake:

 

 

kastein - Do your self a favor, and tear all that junk out of there, and get rid of the load sensing valve, and read the post on running ONE hard line to the rear.

 

The less lines and connections, twists and turns you have, the better chance you'll have less problems latter on.

First - yeah, "what a tangled mess" is the first thing I thought too :D

Second - I want to keep the load sensing valve as I go from an empty bed to 1000+ pounds of stuff at random fairly frequently. I also trust the brake line work I do, and I'm under there frequently enough that I should catch rust long before it becomes a problem again. The only thing the system really adds that would reduce reliability is the valve itself, and mine looks to be in excellent shape.

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I'll agree........

 

........IF your load sensing valve is in working condition.

 

The problem is, alot of them are not, and there are NO replacement parts available, nor the tools to service them.

 

I just cringe when I see something like you found under there :eek:

 

Good Luck ;)

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I'll agree........

 

........IF your load sensing valve is in working condition.

 

The problem is, alot of them are not, and there are NO replacement parts available, nor the tools to service them.

Yeah, if it turns out it doesn't work (anyone know how I can test it before plumbing the bypass line? I'd rather not waste time if it's completely FUBAR, I didn't see a test procedure in my FSM when I checked last night) I am going to eliminate it and never look back.

 

I just cringe when I see something like you found under there :eek:

 

Good Luck ;)

You and me both... the rest of the lines that I already replaced were WORSE. Mostly made of rust, tangled all over the place, spliced with compression joiners everywhere... it was terrible. It was an accident waiting for a place to happen.

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:rotfl2:

 

That's how I got my driver now, well, 6 years ago, the rear brake lines were shot, and the guy dropped the price $250 just to get rid of it........he had compression fitting on the lines and couldn't get it to stop leaking.......... :teehee:

 

And the scary thing was........he was a race car driver :eek:

 

I guest his pit crew didn't work on this MJ :dunno:

 

But.......his soul is resting now, he passed about 1-1/2 years after I bought the MJ from him, and I can't ever get rid of it, because one of his old friends lives across the street from me, and every time I talk to her, she reminds me that it was Vinny's Jeep.

 

Unless I move......... :roll:

 

I don't know of any way to test it, if it's working or not......

 

In my '89 FSM on page 5-5 it shows the adjustment......and the 'special' tools needed, but no mention if it even works after the adjustment :dunno:

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They can be tested by installing a "tee" fitting w. a hydraulic gauge on the input and output sides of the valve to see if the valve increases or reduces pressure as it should when moving the arm. Used to do this back in my old Cal Lab days for aircraft hydraulic systems. :cheers:

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:rotfl2:

 

That's how I got my driver now, well, 6 years ago, the rear brake lines were shot, and the guy dropped the price $250 just to get rid of it........he had compression fitting on the lines and couldn't get it to stop leaking.......... :teehee:

 

And the scary thing was........he was a race car driver :eek:

 

I guest his pit crew didn't work on this MJ :dunno:

 

But.......his soul is resting now, he passed about 1-1/2 years after I bought the MJ from him, and I can't ever get rid of it, because one of his old friends lives across the street from me, and every time I talk to her, she reminds me that it was Vinny's Jeep.

 

Unless I move......... :roll:

 

I don't know of any way to test it, if it's working or not......

 

In my '89 FSM on page 5-5 it shows the adjustment......and the 'special' tools needed, but no mention if it even works after the adjustment :dunno:

yeah, this whacky "85 degree" tool or whatever it is. Saw that :( bets on being able to buy one from Jeep? :rotf:

 

Great idea on the hydraulic gauge and tee fitting, I'll have to see if I can rig that up.

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And thanks to Mr. Hornbrod for coming up with the perfect solution.......again :yes:

 

:cheers:

 

Makes total sense to me on how to test if the load valve is really working.

 

Yes, the tools for testing/installing the valve............ :dunno:

 

The only thought is.........to make something similar to what you need, or improvise something to do the function.........I don't think you'll ever find the tools :(

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