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ATL ZJ
06-29-2009, 05:37 PM
I've been having this problem for a little while. On very steep hills, after 20 minutes or so, my brakes start to SUCK. Like slide 10 feet back while you're pumping the pedal, and then they barely grab and stop the rig. The rears seem to be doing all the work before I pump the fronts back to life and the rig comes to a stop. Once I'm back on flat ground, brakes are normal again. On flat ground and non-insane grades they stop the rig very well.

The system is pretty simple. 1980s Ford e350 master, 1988 XJ booster, '86 Ford 1 ton calipers front, '85 GM 3/4 ton calipers rear. The only other part of the system is an electric line lock, which I do keep on while parked on steep hills. It locks pressure to the rear brakes only.

My best guess is that air must be getting into the system somehow.

slim616
06-29-2009, 06:27 PM
when you say "On very steep hills, after 20 minutes or so, my brakes start to SUCK" Is that working the hell out of them, just sitting there or a combination of both?

ATL ZJ
06-29-2009, 07:30 PM
Both. I'll give two examples.

Heading down hill at a park a couple hours from home. The descent from the main trails back to the loading area is basically straight down a mountain without any switchbacks. Took 5-10 minutes to get to the bottom and by the end, I found myself leaving the rig in gear and compression braking it down, as well as pumping the brakes pretty good. So in that situation, they did get worked pretty hard before showing any symptoms.

Second situation. On a steep trail in Arkansas. We had been on this trail for about 30 minutes. Just a long loose climb with a couple vertical ledges. Not the steepest trail I've ever been on, but very tough to walk on foot. After the second ledge, I park the rig, leave it in gear and apply the line lock. 15 minutes later, climb back in after everyone is up the ledge. Release the line lock (with my foot on the brake) and start slipping backwards. Pumped the pedal 6-7 times and it creeps to a stop. A couple more pumps and I would have switched pedals, revved to 4 grand, and dumped it into a forward gear. This is the case where I wouldn't consider them overworked but the frightening effect is the same.

Bort62
06-29-2009, 08:10 PM
The first scenario sounds like brake fade. Stock pads suck balls, I use Porterfield R4S on mine.

Couple months ago we were all heading down a fairly steep grade and the other two jeeps had to stop and let the brakes cool off - mine were still gripping fine.

The second situation however sounds like something else. Not really sure there.

Stock brake compounds really do suck tho. Their stopping power falls off dramatically with heat.

Technohead
06-29-2009, 09:04 PM
This is why I love my Scout II with T-98 (6.4:1 first gear) and Dana 300 Tera-low (4:1 low range); brakes are optional, which was a good thing back when it had drums on all four corners.

Like Bort62, my guess is the brake pads. Stock brake pads suck but even high-end brake pads suck when you run them through the dirt and mud for a little while. Have you noticed much difference with new pads? We run alot of dirt and mud around here so it is common practice to swap out the pads pretty often; even as frequently as every six months.

Having said all this, the bit about pumping the pedal is strange. If air was in the lines then I think it would be noticeable even on flat ground. Do you think it would have made any difference if instead of pumping you just kept pushing?

rstrucks
06-29-2009, 09:08 PM
It sounds like you need a pair of brake residual valves. They keep fluid from bleeding back into the master cylinder when the calipers are higher than the MC (scenario 2, correct?). If fluid flows back the calipers basically "lose their prime" and need to be pumped back up. Residual valves are typically used in hot rod applications where the MC is installed under the floor (or any where lower then the calipers). They have two different types; one for drums and one for two discs. IIRC they are 2 psi for discs and 10 psi for drums.

Ken L
06-29-2009, 09:11 PM
In the second scenerio, it sounds like the line lock held the pressure in the system behind it, and once you released that pressure the entire system couldn't "brake" correctly. It sounds to me like the issue is from the line lock forward somewhere in the system.

Proportioning valve OK? I assume there's no seeping visible. Does the master cylinder hold fluid or is there a loss?

Just a couple of the things that I would check out.

rstrucks
06-29-2009, 09:15 PM
http://tbn2.google.com/images?q=tbn:XWASSHxX6DvaRM:https://www.4wdfactory.com/store/product_images/m/residual_valve__27443.jpg (http://images.google.com/imgres?imgurl=https://www.4wdfactory.com/store/product_images/m/residual_valve__27443.jpg&imgrefurl=https://www.4wdfactory.com/store/products/Brake-Residual-Valve.html&usg=__ufrh_aNE-1WI9T9mLWORotC1GPM=&h=213&w=275&sz=16&hl=en&start=4&um=1&tbnid=XWASSHxX6DvaRM:&tbnh=88&tbnw=114&prev=/images%3Fq%3Dresidual%2Bvalve%2Bbrake%26hl%3Den%26 sa%3DN%26um%3D1)[/URL]
[URL="http://images.google.com/imgres?imgurl=http://www.rallydesign.co.uk/images/260-1874.jpg&imgrefurl=http://www.rallydesign.co.uk/index.php%3FcPath%3D562_596&usg=__kPeYZS4cYU1vmt0FHn3BFTuvLWU=&h=430&w=430&sz=17&hl=en&start=69&um=1&tbnid=4d-qfXMFySzwiM:&tbnh=126&tbnw=126&prev=/images%3Fq%3Dresidual%2Bvalve%2Bbrake%26ndsp%3D18% 26hl%3Den%26sa%3DN%26start%3D54%26um%3D1"]http://tbn2.google.com/images?q=tbn:4d-qfXMFySzwiM:http://www.rallydesign.co.uk/images/260-1874.jpg (http://images.google.com/imgres?imgurl=http://piratejack.net/troubleshooting/valveFAQ_files/discdrum2.jpg&imgrefurl=http://www.piratejack.net/Tech-Support/Typical-Brake-System-Configurations.html&usg=__imjOjh3XAjDD9kXmiBjTLMAdmLk=&h=163&w=321&sz=7&hl=en&start=35&um=1&tbnid=JA0dNt9MkFB3JM:&tbnh=60&tbnw=118&prev=/images%3Fq%3Dresidual%2Bvalve%2Bbrake%26ndsp%3D18% 26hl%3Den%26sa%3DN%26start%3D18%26um%3D1)

ATL ZJ
06-29-2009, 09:53 PM
The first scenario sounds like brake fade. Stock pads suck balls, I use Porterfield R4S on mine.

Couple months ago we were all heading down a fairly steep grade and the other two jeeps had to stop and let the brakes cool off - mine were still gripping fine.

The second situation however sounds like something else. Not really sure there.

Stock brake compounds really do suck tho. Their stopping power falls off dramatically with heat.

Porterfield R4S sounds like something I should be drinking. ;) Seriously though, the pads are what I'd consider to be decent quality. Middle of the road Napa pads. Hopefully that is not too subpar for those with more refined tastes in ceramics/metallics here.




Like Bort62, my guess is the brake pads. Stock brake pads suck but even high-end brake pads suck when you run them through the dirt and mud for a little while. Have you noticed much difference with new pads? We run alot of dirt and mud around here so it is common practice to swap out the pads pretty often; even as frequently as every six months.

In both cases, the ground and pads were both dry. Every component of this entire system was brand new 9 months/~300 miles ago (minus the rotors, which were turned and the MC and booster). The rotors are 12.5" in diameter for crying out loud, and the calipers are massive enough to require 17" wheels to avoid any caliper grinding. Even the worst pad on the market should be able to perform adequately given the abundance of surface area it's provided.


If air was in the lines then I think it would be noticeable even on flat ground. Do you think it would have made any difference if instead of pumping you just kept pushing?

So did I. No, the pedal got soft and traveled almost to the floor very easily... it felt like air in the system.


It sounds like you need a pair of brake residual valves. They keep fluid from bleeding back into the master cylinder when the calipers are higher than the MC (scenario 2, correct?). If fluid flows back the calipers basically "lose their prime" and need to be pumped back up. Residual valves are typically used in hot rod applications where the MC is installed under the floor (or any where lower then the calipers). They have two different types; one for drums and one for two discs. IIRC they are 2 psi for discs and 10 psi for drums.

Yes, the calipers were much higher than the master in the second scenario. The residual valves sound exactly like what I need. How do they work? Do they cause any added drag? I assume they're ok to use with both floating and fixed calipers?


. It sounds to me like the issue is from the line lock forward somewhere in the system.

Proportioning valve OK? I assume there's no seeping visible. Does the master cylinder hold fluid or is there a loss?

Just a couple of the things that I would check out.

No seeping, leaking, or fluid level drop in the master. The line lock is installed in the rear brake circuit about 6" downstream from the master. I do not have a proportioning valve.

rstrucks
06-29-2009, 10:02 PM
Yes, the calipers were much higher than the master in the second scenario. The residual valves sound exactly like what I need. How do they work? Do they cause any added drag? I assume they're ok to use with both floating and fixed calipers?


They install in-line with your hard line and basically maintain 2 (or 10) psi in a section of your system so your caliper pistons stay right up against the pads, ready to apply, rather than having to pump/fill them back up with fluid. They won't apply any extra drag worth noting. And yes, they will work with any style caliper.

napajeep
06-29-2009, 11:49 PM
It sounds odd, but the brake fluid you used when you did the word 9 months ago, was it a new bottle (still sealed)? Brake fluid is hydroscopic, if you buy one of the big bottles and you add a little fluid to something, then the bottle sits there for a while, it will absorb water from the atsmosphere, thus putting water into your brake system. This will then lower the boiling point for your fluid, and steam compresses differently. When it cools and condenses, you get semi normal pedal again.

Long winded answer, and totally moot if you used a fresh bottle of fluid.

ATL ZJ
06-30-2009, 09:28 AM
It sounds odd, but the brake fluid you used when you did the word 9 months ago, was it a new bottle (still sealed)? Brake fluid is hydroscopic, if you buy one of the big bottles and you add a little fluid to something, then the bottle sits there for a while, it will absorb water from the atsmosphere, thus putting water into your brake system. This will then lower the boiling point for your fluid, and steam compresses differently. When it cools and condenses, you get semi normal pedal again.

Long winded answer, and totally moot if you used a fresh bottle of fluid.

True. This is common knowledge and yes I have tried to use fresh fluid each time I've bled it. The system has been bled 3-4 times in the past nine months for various reasons (broken driveshaft hit hardline, etc.) I really don't see boiling fluid as the culprit though.

ATL ZJ
06-30-2009, 09:51 AM
They install in-line with your hard line and basically maintain 2 (or 10) psi in a section of your system so your caliper pistons stay right up against the pads, ready to apply, rather than having to pump/fill them back up with fluid. They won't apply any extra drag worth noting. And yes, they will work with any style caliper.

The info I've been able to find on these claims that they are more of a bandaid than a necessary part of a brake system... such as this thread (http://pirate4x4.com/forum/showthread.php?t=738390&highlight=residual+valve).

I have no problem installing one of these valves, but I have to wonder why other guys who are wheeling on similar terrain don't need them in their systems.

CruisinGA
06-30-2009, 01:17 PM
I don't think it's boiling point- as long as your brake lines aren't wrapped around your headers. (you have bled both your front&rear brakes recently too, right?)

I'm not completely convinced you need a residual valve. (Land Cruiser M/C's have them built in- does your E350 master not?)
I wouldn't call residual valves a "bandaid," they're just not needed in all situations. Billavista himself said they are often required in situations where the caliper is higher than the master cylinder, and you are creating such a situation intermittently. You said yourself that the rear brakes, (still below the master cylinder) do not have the problem, only the front (above the master cylinder).

Mr T (toyota) designed disc brake M/C's with a 2lb residual valve for master cylinders mounted on the firewall. I can't imagine it was because they weren't needed. Maybe it was because Toyota actually anticipated people using their vehicles off road. :D

I do think the problem is upstream of the line lock- otherwise why would the line lock hold well on an incline?

I'm suspicious of your all-cast master cylinder not holding enough fluid to cover the inlet from resevoir to cylinder on steep inclines. If this was the case, if you bled your brakes right now, you would find some air. Easy to rule out.

I do know that my Land Cruisers don't have any problems like this so you should probably just switch to all Land Cruiser brakes. I will help you find parts.

I would start with bleeding brakes just to see what you see. Then determine if your E350 master has built in residual valves or not. Run a few tests parking your jeep on top of pop's Lexus and pay close attention to what happens.

All of this is just for the problem you are having parked on inclines. I'm not sure that the other problem (long downhill) is related.

Bort62
06-30-2009, 01:45 PM
I'm suspicious of your all-cast master cylinder not holding enough fluid to cover the inlet from resevoir to cylinder on steep inclines. If this was the case, if you bled your brakes right now, you would find some air. Easy to rule out. I would suspect this as well.

ATL ZJ
06-30-2009, 02:38 PM
I'm suspicious of your all-cast master cylinder not holding enough fluid to cover the inlet from resevoir to cylinder on steep inclines. If this was the case, if you bled your brakes right now, you would find some air. Easy to rule out.

This was our hypothesis on the trail as well. But after popping the lid off the MC once back on flat ground, it doesn't look possible that the fluid level could drop below the inlet port. You can see where the hole is at the bottom of the back reservoir for the rear brake circuit but unfortunately you can't see the inlet for the front circuit. The e350 is the one on the right.

http://www.jeepaholics.com/support/files/92greenyj/20060316133120_DSCN0583.jpg

I can certainly bleed the system again to test it. Should I also try to crack the lines at the MC to try and bleed it also? Or winch the front of rig up into the air and bleed the system that way??

CruisinGA
06-30-2009, 04:06 PM
I don't think it would hurt to winch the front of the rig up in the air and at least see what is going on. Winch little by little and try the brakes as you go. I've got a branch that is screaming for a winch line to be thrown over it.

The rear circuit is never the problem, right? Where is the front circuit inlet, at the front of the resevoir?

paulkeith
06-30-2009, 08:21 PM
does your brake performance return as soon as you pump it a couple times? or does it have to sit for a couple hours on flat ground to get adequate performance back?


my gut reaction upon reading your first post was to add some residual pressure valves, 2psi for discs. but if the performance isn't back to 100% as soon as you're level and pump the pedal a few times, i'd suspect you're getting air in the system somehow and its taking time to float back out.

Paul

rstrucks
06-30-2009, 09:04 PM
My money is still on just needing a residual valve. In your situation I don't think it is a band-aid. I'm guessing the reason this is not a more common problem is that most guys normally park on somewhat level ground, even when on steep terrain they wait to park until they find a somewhat flat spot. Having your rig sit for extended periods of time with the front calipers above the MC is not typical.

Do you have a good solid pedal normally?

You shouldn't have to crack the lines at the MC. Any air that would have escaped there will escape at the caliper bleeder.

ATL ZJ
07-01-2009, 12:12 AM
I've got a branch that is screaming for a winch line to be thrown over it.

You know I will winch my rig into your tree right? :D


The rear circuit is never the problem, right? Where is the front circuit inlet, at the front of the resevoir?

Rear circuit acts fine as far as I can tell. No problems when like lock is applied or otherwise.


does your brake performance return as soon as you pump it a couple times?

Brake performance is great as soon as the rig is on level ground. I tested it 15 seconds after cresting the big hill and locked them up no problem. In normal driving conditions and on shorter climbs, the brakes stop the rig great.


My money is still on just needing a residual valve. In your situation I don't think it is a band-aid. I'm guessing the reason this is not a more common problem is that most guys normally park on somewhat level ground, even when on steep terrain they wait to park until they find a somewhat flat spot. Having your rig sit for extended periods of time with the front calipers above the MC is not typical.

It just seems to me that a system could be designed that doesn't need a residual valve to overcome gravity. My needs are usually not typical... and I want my brake system to be able to do that! :D I guess I'm confused because it seems like gravity causing fluid to leak back into the MC could itself create a vacuum that would prevent fluid from leaking any more. Sorry if I'm not explaining this well, but it makes sense in my head.


You shouldn't have to crack the lines at the MC. Any air that would have escaped there will escape at the caliper bleeder.

If there was originally air in the lines at the master, it could float up to the calipers on steep hills? Theoretically, shouldn't we be bleeding the highest point in the system (MC on flat ground, front calipers in winch-up-a-tree scenario)? Bleeders are at the highest point on a caliper, so shouldn't our final bleed point also be?

Thanks for the help guys. Not trying to be difficult, just thinking through it all before I dive into it this weekend.

CruisinGA
07-01-2009, 08:15 AM
It just seems to me that a system could be designed that doesn't need a residual valve to overcome gravity. My needs are usually not typical... and I want my brake system to be able to do that! :D I guess I'm confused because it seems like gravity causing fluid to leak back into the MC could itself create a vacuum that would prevent fluid from leaking any more. Sorry if I'm not explaining this well, but it makes sense in my head.



If there was originally air in the lines at the master, it could float up to the calipers on steep hills? Theoretically, shouldn't we be bleeding the highest point in the system (MC on flat ground, front calipers in winch-up-a-tree scenario)? Bleeders are at the highest point on a caliper, so shouldn't our final bleed point also be?


You probably could make it work without residual valves, but maybe residual valves are the easiest way!

What you're saying about the vacuum is partially correct, it would take a long time for the fluid at the caliper to drain out of the brake line because at the same time the fluid is draining out, air has to be replacing it.
I would focus on the problem that occurs after the line locks have been used. In that case you KNOW the pads are close to the rotor, and downstream of the line lock there is no air. The ONLY place there could be air is between the master and the line lock, and the ONLY way it could be getting into the lines is through the master itself.

The reason we don't bleed at the highest point is because that also happens to be where the resevoir is. Brake fluid is viscous enough and fluid velocity high enough when bleeding that the air bubbles move down and out of the system with it.

rstrucks
07-01-2009, 09:47 AM
Thanks for the help guys. Not trying to be difficult, just thinking (way too much) through it all before I dive into it this weekend.

Fixed :D

rstrucks
07-01-2009, 09:55 AM
It just seems to me that a system could be designed that doesn't need a residual valve to overcome gravity. My needs are usually not typical... and I want my brake system to be able to do that! :D I guess I'm confused because it seems like gravity causing fluid to leak back into the MC could itself create a vacuum that would prevent fluid from leaking any more. Sorry if I'm not explaining this well, but it makes sense in my head.



If there was originally air in the lines at the master, it could float up to the calipers on steep hills? Theoretically, shouldn't we be bleeding the highest point in the system (MC on flat ground, front calipers in winch-up-a-tree scenario)? Bleeders are at the highest point on a caliper, so shouldn't our final bleed point also be?


You could design a system that would prevent a gravity bleed back but you'd have to mount your MC on top of your cage!

When the fluid is slowly draining back into the MC the caliper piston is also slowly moving away from the pads/rotor so no vacuum is created. That is why you have to pump the pedal to get your brakes functioning again. Also, if you had air in the system you would have a spongy pedal all the time not just after sitting at an angle. And I've never heard of air escaping back up through the MC after it had gotten into the system, any volume of air large enough to give you a soft pedal would require being forced out through bleeding.

You can do a "reverse" bleed of the brakes. There are bleeder kits out there that force the fluid from the caliper bleeder valve back through the system and up through the MC. I've never tried it personally so I can't say how well it works.

chadjans
07-06-2009, 02:42 AM
I like this thread.

I too had a brake pedal go to the floor when I was driving over this two sided RTI ramp.

http://www.mallcrawlin.com/forum//attachment.php?attachmentid=4246&stc=1&d=1238476242


It went to the floor when I crested the top and started driving over the other side. I was thinking of adding some resudial valves to my system.

chadjans
07-06-2009, 02:51 AM
I guess my next question would be; how close to the master do the valves need to be?

rstrucks
07-06-2009, 02:39 PM
Doesn't really matter. Anywhere between the MC and where it "T's" off into two lines would work. I would put them where it is easiest to install them.

chadjans
07-06-2009, 05:55 PM
Can one get by with a pair on the front brakes only? Or is a pair needed for the rears?

ATL ZJ
07-06-2009, 06:05 PM
Hmm.. I was planning on getting of these as soon as I can figure out what steering ujoint I need and ordering it all together. But Chad raises a good question... do I need one valve per caliper, as he is suggesting, or just one valve before the lines "T" off like Ryan is saying?

chadjans
07-06-2009, 06:13 PM
Hmm.. I was planning on getting of these as soon as I can figure out what steering ujoint I need and ordering it all together. But Chad raises a good question... do I need one valve per caliper, as he is suggesting, or just one valve before the lines "T" off like Ryan is saying?

I am thinking three. One for the rear and two for the front. The rear somewhere in line before the axle housing t. (unless one for the rear is too much fluid volume to hold back) And one for each caliper up front. Probably between the hard line and the flex line to each caliper.

Order your steering shaft from PSC.

ATL ZJ
07-06-2009, 06:59 PM
I am thinking three. One for the rear and two for the front. The rear somewhere in line before the axle housing t. (unless one for the rear is too much fluid volume to hold back) And one for each caliper up front. Probably between the hard line and the flex line to each caliper.

Why do you say that? Because of the greater volume of the front calipers, or some other reason? I had been thinking one valve in the front would do the trick.


Order your steering shaft from PSC.

I'd really prefer to build my own. I'm sure PSC's shafts are good and your buddy Andrew is a good fellow to do business with, but who even knows how long I'll be running a steering shaft this length. No sense in putting a ton of coin into something temporary.

rstrucks
07-06-2009, 07:49 PM
One will be fine for the front. You can do two in the front if you really want to, but there is no advantage.

Ramsport59
07-06-2009, 09:37 PM
I ran into the same issue with my ZJ loosing brake on bad nose dives....It ended up being the combination of sucking air thru the outlet of the master cylinder and my front rubber brake lines swelling.....Replaced the front lines and hoping to see if it helped......

Rick

chadjans
07-07-2009, 03:24 AM
Why do you say that? Because of the greater volume of the front calipers, or some other reason? I had been thinking one valve in the front would do the trick.



I'd really prefer to build my own. I'm sure PSC's shafts are good and your buddy Andrew is a good fellow to do business with, but who even knows how long I'll be running a steering shaft this length. No sense in putting a ton of coin into something temporary.

Because of my plumbing around the master. Easier to put them down by the frame rail mounts. I did read somewhere on pirate that the valves are to go between the master and the prop valve. I am running an adjustable prop on the rear.

So is there anything diffinitive stating they should be run front and rear, front only or rear only?

Probably best for a better thread but how much is that flaming river stuff? FYI I used a stock shaft, just shortened it and reused the universal to hook up to my orbital. I was just stating PSC for the universal and shaft still allowing you to build your own.

ATL ZJ
07-07-2009, 10:47 AM
Well I was thinking front only, since the front does the majority of the braking and my rears have always seemed OK. But maybe it would be smart to plumb one in the rear circuit also. Did you notice an improvement in your braking balance/performance after installing your prop. valve? Or have you had it installed from the get-go on your new setup?

...I guess it's OK to derail this thread a bit. I found a spare ZJ steering shaft I had laying around :o and was just going to shorten it to match the length of my current one. Then add a new joint to it that fits the psc column attached to my orbital. The flaming river joints run about $75, but I only need one, and I think it will be worth it to get rid of the bind from my existing hacked-together steering shaft.

chadjans
07-08-2009, 03:31 PM
Well I was thinking front only, since the front does the majority of the braking and my rears have always seemed OK. But maybe it would be smart to plumb one in the rear circuit also. Did you notice an improvement in your braking balance/performance after installing your prop. valve? Or have you had it installed from the get-go on your new setup?

...I guess it's OK to derail this thread a bit. I found a spare ZJ steering shaft I had laying around :o and was just going to shorten it to match the length of my current one. Then add a new joint to it that fits the psc column attached to my orbital. The flaming river joints run about $75, but I only need one, and I think it will be worth it to get rid of the bind from my existing hacked-together steering shaft.

I had a prop valve from the get go. I removed the oring in the non adjustable oe prop valve long ago for my 8.8 swap. My D35C had drum brakes. I wanted to be able to tune the bias. I am thinking of redoing the plumbing near the master between it and the oe hard lines with some russell universal brake hoses: http://www.russellperformance.com/mc/brake_hoses/universal.shtml

I have used these on several builds and REALLY like them. Easy to use and a very nice hose.

Since I know you are smart enough to not put your steering valve in your cab copartment a stock steering column assembly should work for you. I made mine work. Needed NO adapter to mount the existing end of the column to the orbital. Bolts up with: (I think this is the one, I could be wrong though!) http://www.pscmotorsports.com/fhclc04d-475-column-w-3436-spline-gm-p-651.html

ATL ZJ
07-08-2009, 04:02 PM
I thought about just swapping the column. I use a 13/16" - 36 spline PSC column now because it was the same size as the shaft I modified to fit my old J20 box. I guess I could buy the column you have and then just shorten my OE ZJ steering shaft. But then I would not have an easily swappable spare steering shaft (not that I should need one, or that my spare would be that great anyway). Since the columns are the same price as the ujoints, it's kind of a wash. But maybe swapping the column would be more foolproof.

Can anyone confirm if stock ZJ boxes/shafts are 3/4" -36 spline?

chadjans
07-08-2009, 04:21 PM
Can anyone confirm if stock ZJ boxes/shafts are 3/4" -36 spline?

I have been told that they are 36 spline GM. When my parts guy orders them from PSC he always asks for the Jeep column.

If I remember correctly my quick release Grant steering wheel hub is 36 spline GM.

chadjans
07-24-2009, 05:18 PM
Anyone installed some valves to see if the problem still exists?:doh:

ATL ZJ
07-24-2009, 05:23 PM
Anyone installed some valves to see if the problem still exists?:doh:


Got my residual valve and will be plumbing it in to the front circuit this weekend.

Also, the OEM jeep steering shaft/box is 3/4" 30 spline ;) Hopefully psc will get my replacement column back to me before thursday next week!

chadjans
07-24-2009, 05:44 PM
Is it different spline / diameter at the steering wheel than it is at the steering gear?

ATL ZJ
07-24-2009, 06:37 PM
yes

rstrucks
01-19-2010, 11:43 PM
Cam, I was searching something else and stumbled across this thread. Did you ever get the residual valve installed? Did it fix your problem?

Just curious.

ATL ZJ
01-20-2010, 01:13 AM
I've only tested it 6 days on the trail so far because my rig has been down since September, but it seems to work well... I'm not sure how much is placebo and how much is actual performance improvement, but I'm happy with the result.

On my last trip to mountain city I was on some inclines that were steep enough for the fuel to drain back away from the fuel cell pickup tube and the motor to starve for fuel, even with 3/4 of a tank, but the brakes felt great. Now that I have my walbro pickups installed I should be able to do even more testing :D

zjeepin
01-20-2010, 11:44 AM
so what PSI residual valve are you running? Im thinking of plumbing them in for good measure

ATL ZJ
01-20-2010, 12:08 PM
so what PSI residual valve are you running? Im thinking of plumbing them in for good measure

I went with a 2psi wilwood valve (the blue one) in the front circuit only. figured the larger front brakes do a lot more on a steep downhill descent even if the rear circuit does "lose its prime". Plus I am usually in my lowest gear while dropping off stuff anyway.

zjeepin
01-20-2010, 12:28 PM
sweet, thanks...

rstrucks
01-20-2010, 03:40 PM
Yeah, the 10 psi valves are designed for drum brakes which require a bit more preload/prime than discs.

zjeepin
01-20-2010, 05:02 PM
I went with a 2psi wilwood valve (the blue one) in the front circuit only. figured the larger front brakes do a lot more on a steep downhill descent even if the rear circuit does "lose its prime". Plus I am usually in my lowest gear while dropping off stuff anyway.


i was looking at those valves and they have npt ports on them, is there an npt to flare adapter to go with them?

ATL ZJ
01-20-2010, 05:05 PM
i was looking at those valves and they have npt ports on them, is there an npt to flare adapter to go with them?

yeah speedway stocks a bunch of adapters, I think I bought mine from them.