Failed Prop Valve?

[jjzepplin]

I changed my front brake pads once and when I collapsed the caliper it sent a bunch of crud into the brake line and clogged it. Made for a bad experience. There really can be a bunch of crud in there.

[jastewart25]

Originally Posted by jjzepplin

I changed my front brake pads once and when I collapsed the caliper it sent a bunch of crud into the brake line and clogged it. Made for a bad experience. There really can be a bunch of crud in there.

i thought it was an internally collapsed brake hose but no.

i have:

replaced both right and left front calipers
new front brake hoses
new fluids
new tires (came with truck from po)
checked lift/leaf springs/ball joints/bushings/control arms
axles looks good
pads from po weren't even half warn so i kept them. evenly warn at that.

i understand the ride after lifting won't be the same as before, but man, every lifted square cannot possibly brake like this!

the lightest of taps on brakes turns my wheel to the right and the harder i push the more drastic it is on highway.

funny thing is when i'm on my miles of gravel roads it does it much less. of course i am traveling at a much slower speed never really above 20.

i guess i'll try replacing the prop valve.

is anyone optimistic i can fix this? if not i'm going to have to sell it and be heartbroken.

i need a square i can safely drive on the road.

[hatzie]

With the big lift you have on the truck you need to modify the steering to operate properly.
The Dana 44, Dana 60, and GM 10 bolt front axles with a big lift, big tires, and lift kit modified push pull steering linkage can and will shear off the leaf spring pack locator pin causing the axle to slide on the spring pack during braking and cornering.
A Crossover steering setup will supposedly make a lifted truck handle much better at highway speeds. It'll never have the same road manners as a mildly lifted or stock ride height truck but it'll make it better than it is. This is the main reason I took 4" of the 6" lift out of my 76 suspension. At 6" up she felt very loose and unruly on the highway with brand new ball joints and tie rod ends.

Google Push Pull VS Crossover steering and do some reading.

[Koffer]

Originally Posted by jastewart25

pads from po weren't even half warn so i kept them. evenly warn at that.
.

I didn't see this before , as stated above you just might have contaminated pads . They will get very grabby . With the amount you have tossed at this so far buy a cheap set of pads(under $20 at autozone) and put them on . Or if you don't want to just swap them from side to side and see if it pulls to the other side

[andrewmp6]

Originally Posted by jastewart25

no blocks. all leaf springs. had a guy who specializes in lifts at his shop check it out. can't find a single thing wrong with lift.

as far as steering, everything is tight and good. no play whatsoever.

no brake drag.

now i'm going back to maybe it is the prop valve??

You have lift blocks in the rear of it,And they look a good 4 to 6 inches from that picture.With a 4 inch lift and stock steering it will pull one way when you hit a bump because the steering is to short for the lift.

[jjzepplin]

Mine has a 4" suspension and 3" body lift and handles pretty good. Huge difference in handling with aluminum wheels and 10 ply tires. I think the old steel wheels were flexing at the hub and the tires were Cepek bias ply. Thing was all over the road and quite frankly dangerous. I put new axles and a steering block raising the front steering arm and Steering absorbers. Now it even has a front sway bar. Solid as a rock!
Have you bled the brakes? That is how I found my problem with the caliper. Heavy foot on the pedal and just a trickle out of the caliper. I rebuilt them and the piston was just plain stuck in there with crud. Maybe the po put it together that way I don't know. But who knows what any of the po's do with these rigs. I think a total brake job and purging all the lines is in order. You could find your problem you might not. But you would be sure you had good brakes!
Have you checked the steering box mounting on the frame for cracks? NOTORIOUS! If it doesn't have a brace on the steering box or some sort of reinforcement you should really think about putting one on there...If it isn't cracked there-it will be soon...
Prop valves are only front to rear as mentioned before. Nothing to do with left to right. It only shuts either the front or rear off due to fluid loss or a possible broken line leaving you with enough brakes to still stop. If it was bad or not working your brake light would be on. Unless the bulb was bad. Is your wire still connected to the switch on the valve?

[SCOTI]

I agree w/others that is likely not the prop valve. But.... replace it & you'll be able to check it off the list off possibilities.

http://inlinetube.com/Prop%20Valves/pro_valves.htm

[Just call me Sean]

Originally Posted by jjzepplin

It only shuts either the front or rear off due to fluid loss or a possible broken line leaving you with enough brakes to still stop.

No, it doesn't do that. The older ones did, the ones paired with a single reservoir master cylinder. These just balance the front and rear.

[jastewart25]

Originally Posted by hatzie

Diving to one side is symptomatic of poorly adjusted toe or badly off camber and or caster angles. Camber and Caster are not adjustable on most GM solid axles... If they are off then something may be bent.
Lifted trucks are reputed to follow the ruts and road grooves a bit more aggressively than stock so that's not a good indicator of adjustment issues.

i think you may be on to something here hatzie. really, i just don't know what else it could be at this point.

[jastewart25]

Originally Posted by hatzie

The Dana 44, Dana 60, and GM 10 bolt front axles with a big lift, big tires, and lift kit modified push pull steering linkage can and will shear off the leaf spring pack locator pin causing the axle to slide on the spring pack during braking and cornering.

absolutely zero axle slide. u bolts are good. no indication of sliding. as well as repeatedly gaining speed slamming on breaks as others watch axles and tires just to double check!

[slotard]

I suspect it has to do with your steering geometry related to the lift. A lifted solid front axle truck does a lot better with crossover steering. Otherwise, you end up with the problem you have.

[jastewart25]

thank you all for your replies.

here is the updated list of what has been checked:

new calipers
new hoses
new fluids
new brake pads (old ones were perfectly good and symmetrically worn but glad i changed just to eliminate)
bled the brakes
swapped right tire with left tire

-rotors are completely even. not one mark on them to indicate uneven wear.

-ubolts are top notch. no indication of axle slide whatsoever.

-steering box has zero cracks in it. aftermarket steering wheel (one of those small wheels)

-tires were spun. nothing off no drag.

-hubs are warn manual locking hubs so not original no problems there.

-steering stabilizer all good.

-has a sway bar.

-all bushings check out fine.

worst pull is definitely on highway. steering wheel jerks slightly left as truck dives right. each time.

does not dive when hitting a bump. steering wheel feels rock solid. when i turn it turns. no play.

pull is ONLY upon braking yet brakes check out. ????

the truck has a 4 inch lift. not sure of the brand? all done by po

would like to explore the lift being the culprit but not sure how i would go about trying to figure that one out.

and i have a mechanic of a million years who owned 2 different squares with pull issues working on this. he can't figure it out either and it's driving both of us nuts.

sounds silly but could it be the tires? it came with mickey thompson mtz's. not sure of the size but i will include photos.

any help is appreciated.

it's gotta be something!

included are photos of rotors/brake pads from po that were removed and replaced/ubolts on leaf springs front right

[jastewart25]

sorry, having a hard time with photos for some reason

[jastewart25]

if it is steering related, what is the best way to diagnose that? what would be a good starting point i guess is what i am asking.

thank you all again!

[jastewart25]

as for steering i don't believe it suffers from any of these. will check again tomorrow.

Bump Steer: If the steering angles are not proper, the energy caused by a tire going over a bump or hole will be transferred through the steering system to the steering wheel--where you will feel a ''bump''. This can be dangerous-especially in emergency situations.

Memory Steer: When you turn your wheel and then release, the wheel should go back to center pretty much on its own. If the steering angles are not geometrically correct, the wheels can tend to stick in the turned position. This can be dangerous-especially in emergency situations.

Reduced Turning Radius: This is another problem caused when steering components are not properly aligned-you will not be able to make as sharp of turns as you did prior to installing your lift. Fortunately, there are solutions to these problems...unfortunately, each make and model is different and what works for one may not work for another. You may need a drop pitman arm, or a raised steering arm, you may need a combination of a drop pitman and an adjustable drag link, or a raised steering arm and adjustable drag link. The links on this page will help you determine what your vehicle will need. The steering components we sell are heavy duty, forged and heat treated with correct taper of mounting holes to allow for simple and secure installation.

[slotard]

If the problem is what I suspect, it's due to poor design rather than any part failures. When the suspension compresses, the front axle moves back and up, which makes the drag link make the wheels turn right.

I just recently bought my truck and it's a C rather than a K, so I don't know much about Chevy steering. However, this is a common problem when it comes to lifted trucks without the right steering modifications. Crossover steer is the way to solve it.

http://offroaddesign.com/catalog/Dana44crossover.htm is a good solution.

[jjzepplin]

I don't see any front axle shims. Mine has them. Have you checked your spring bushings? If they are bad or original that might be an issue. That is the next thing I am going to do to mine. Then the x-over steering. Just cuz I am going back to Cali someday and stopping in Utah to see some awesome sights and do some crawling and then to the Rubicon in Cali. Been there several times before but in the Blazer. FWIW I had the same exact parts in two trucks and they both acted identical. Then I swapped those shims around and finally got my results-ten years later. I have thought about putting something like a link system off the top of the spring pads in the front to eliminate the spring wrap but haven't got there yet. I have something like that on the rear called traction bars. I would disconnect them for wheeling but are great for towing.

[72MARIO]

Are the rear brake s adjusted properly ? Could one of the rear brakes not be reaching the drum at the same time as the other 3 wheeles ?

[v30crewcab]

The only real cure is going to be crossover steering. I have 4" lift with 35's, and mine did exactly what yours is doing for years. finally built a crossover setup and it stays straight now when I slam on the brakes. there are vendors that sell the whole setup ready to bolt in.

[jastewart25]

Originally Posted by v30crewcab

The only real cure is going to be crossover steering. I have 4" lift with 35's, and mine did exactly what yours is doing for years. finally built a crossover setup and it stays straight now when I slam on the brakes. there are vendors that sell the whole setup ready to bolt in.

thanks. i believe it does have something to do with this. mine dives right with the lightest of taps on the brakes-no slamming required.

however, i see that crossover steering is really helpful for offroad use? others have said helpful in general. hard to spend all that money if it's really just beneficial for offroad use which i don't really need.

[jastewart25]

Originally Posted by jjzepplin

I don't see any front axle shims. Mine has them. Have you checked your spring bushings? If they are bad or original that might be an issue.

checked bushings today (i think i'm looking in the correct place not mechanical at all) and they look worn.

poly or rubber replacements?

here is a photo of mine.

also, any chance you have a photo of your front axle shims?

NOT SURE WHY MY PHOTOS ARE ALWAYS FLIPPED OR ROTATED UPON UPLOAD. sorry!