Rear Brakes Locking Up

[Keith Seymore]

Joining late, but to reiterate: You need to go by the reservoir size.

On the cast iron units: larger reservoir in front services the front brakes.

WIth the aluminum body units: larger reservoir in rear services the front brakes.

But it is ALWAYS larger reservoir = fronts; small reservoir = rear.

K

M/L Astro/Safari master shown as extreme example:

You must be registered for see images attach

 

[WebMonkey]

i really don't have much to add but;
does the '10' series truck have a valve in the rear?

the one that opens up as the weight in the bed increases?
if it did, and was removed, then the back gets full juice even with no weight on the wheels.

my K20 4K ultra HD does and it still works properly.

the thing i'd check is the rear brake assembly itself.
the OP/first post states a serious noise issue coming from the rear brakes.

shoes not run out at first install and have jumped the guide slot?

sorry i'm not much help

good luck
'monkey

 

[legopnuematic]

i really don't have much to add but;
does the '10' series truck have a valve in the rear?

the one that opens up as the weight in the bed increases?
if it did, and was removed, then the back gets full juice even with no weight on the wheels.

my K20 4K ultra HD does and it still works properly.

the thing i'd check is the rear brake assembly itself.
the OP/first post states a serious noise issue coming from the rear brakes.

shoes not run out at first install and have jumped the guide slot?

sorry i'm not much help

good luck
'monkey

No load sensing valve on a 1/2 ton (that I’ve ever seen).

But I would concur, for op to check the rear brakes out, make sure they are properly adjusted.

If they [the rears] are too far out of adjustment, they will bleed ok, but the pedal will feel off. Stuff like late engagement and not an even braking feel.

Easy test is, if hooked up and operable, click the parking brake a couple clicks and take for quick test, then another couple clicks. That expands the shoes and if braking improves, suggests adjustment is needed.

 

[Andronikos]

Joining late, but to reiterate: You need to go by the reservoir size.

On the cast iron units: larger reservoir in front services the front brakes.

WIth the aluminum body units: larger reservoir in rear services the front brakes.

But it is ALWAYS larger reservoir = fronts; small reservoir = rear.

K

M/L Astro/Safari master shown as extreme example:

You must be registered for see images attach

Google Image Result for https://m.media-amazon.com/images/I/31gx0o9ConL._AC_UF894,1000_QL80_.jpg

This link will show you the exact master on my truck.

 

[AuroraGirl]

No load sensing valve on a 1/2 ton (that I’ve ever seen).

But I would concur, for op to check the rear brakes out, make sure they are properly adjusted.

If they [the rears] are too far out of adjustment, they will bleed ok, but the pedal will feel off. Stuff like late engagement and not an even braking feel.

Easy test is, if hooked up and operable, click the parking brake a couple clicks and take for quick test, then another couple clicks. That expands the shoes and if braking improves, suggests adjustment is needed.

tho a LSV would physically function on a half ton , it was designed to let a 3/4 ton truck use modified brake bias and then when they were unloaded, they could limit the rear when unloaded

 

[Andronikos]

i really don't have much to add but;
does the '10' series truck have a valve in the rear?

the one that opens up as the weight in the bed increases?
if it did, and was removed, then the back gets full juice even with no weight on the wheels.

my K20 4K ultra HD does and it still works properly.

the thing i'd check is the rear brake assembly itself.
the OP/first post states a serious noise issue coming from the rear brakes.

shoes not run out at first install and have jumped the guide slot?

sorry i'm not much help

good luck
'monkey

I have checked them five times. Seriously, five times. Everything is "perfect".

 

[Andronikos]

Just slow, and hold it all the way down until both bleeder screws are closed. Be sure to make sure that the fluid level in the reservoir is OK before you do this and afterwards.

Don't want to run it dry. It's a free experiment if you have brake fluid.

OK, I did this procedure last night and took it for a test. The rears lock up and the fronts don't, just like before. Any other suggestions? I'm willing to go to an adjustable Wilwood proportioning valve and be done with this factory stuff.

 

[Andronikos]

If the only thing that is old is the proportioning valve, why not replace it?

I think you're on to something there. Any suggestions for a reliable replacement?

 

[Andronikos]

Sounds like either the proportioning valve, or you got your lines crossed somewhere between the master cylinder and proportioning valve. Most of your stopping power comes from the front brakes. With the rears locking up and the fronts not engaging makes me think that's your problem.

Any idea where I can get a replacement one that is any good?

 

[Goldie Driver]

OK, I did this procedure last night and took it for a test. The rears lock up and the fronts don't, just like before. Any other suggestions? I'm willing to go to an adjustable Wilwood proportioning valve and be done with this factory stuff.

Well, let's assume the valve is good. Maybe a silly question, but are the longer shoes on the rear ? Rear is the secondary shoe position which is the longer shoe.

 

[Edelbrock]

I think you're on to something there. Any suggestions for a reliable replacement?

Amazon.com : proportioning valve

 

[Old Guy Bill]

There is always some confusion between “Combination” valves and
“Proportioning” valves…
Get a Wilwood valve similar to this one, make sure of the fitting size.
Mount and plumb it into the rear brake line, and adjust it to where the rears don’t lockup.
This is very popular in circle track racing.

You must be registered for see images attach

 

[Blue Ox]

I think you're on to something there. Any suggestions for a reliable replacement?

Here's a wild concept. How about you take yours apart and give it a looksy. You never know what you'll find.

 

[Blue Ox]

There is always some confusion between “Combination” valves and
“Proportioning” valves…
Get a Wilwood valve similar to this one, make sure of the fitting size.
Mount and plumb it into the rear brake line, and adjust it to where the rears don’t lockup.
This is very popular in circle track racing.

You must be registered for see images attach

Just to clarify. A combination valve includes a proportioning valve.

Don't know if adding another one to the equation would cause issues or not.

 

[CalSgt]

A few clarifying questions:

Did the problem exist before replacing everything?

if not did you verify your new wheel cylinders and calipers had the same diameter pistons as the originals?