I'm at a loss..

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PrairieDrifter

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84 k10 suburban. 75ish 12 bolt rear. New brake shoes drums and hardware, wheel cylinders. New master cylinder, the axle hard lines. Soft lines replaced a few years ago with ORD braided lines. the axle has new outer bearings seals and new axle shafts. Almost everything is new.

I've been chasing a brake drag problem. I just can't figure it out. Hardly noticeable till they get real hot, then once real hot they start squeaking, first with light braking, then after sitting at a light or something it'll start almost constantly squeaking and then fully at lower speeds, after enough time driving. Barely noticeable in rpm's, but noticeable.

The drivers side gets hotter, and hotter faster. Which is really throwing me through a loop, doesn't make sense. I've used some old drums and it seemed better at first but now they're adjusted where they want, the old drum is hotter than the other side where I have a new drum that has ALSO been cut down(also confusing). I tried another brand of new drum I believe and I had the same issue right away.

The brakes feel great! They seem to be balanced properly, once the rear shoes are adjusted properly. The rears don't lock up. I can't adjust the shoes off anymore without the pedal suffering, and then it self adjusts back to where it needs to be by itself anyways.

It's pretty obvious it's not a proportioning valve, its acting the same with the new master as with the old. Bleeding brakes was flawless, great flow, little air, definitely not a clogged or collapsed line.

I even thought the axles po had the wrong size brakes for the backing plate. So I tried the 11x2's but they didn't fit right even close. But from my research, these are indeed the big brake backing plates. So the brake size is correct.

Does the 75 ish axle not mix with the 84 master??

I thought maybe the old master was somehow transferring fluid to the rears, and keeping the brakes on, but that's definitely not happening. If the prop valve was the issue I wouldnt have front brakes, if the rears are getting hot. I have front brakes.

Also I know I have good brakes, they stop my 35's just fine. I could try a couple more brands of drums or shoes. But I'm so tired of it, and spending money on shelf parts, or returns.

IM ABOUT TO LOSE MY MIND. I'm about to drop a grand on a disc brake kit. And I really don't want to, not only the money, but the horror stories and mixed reviews.
 

PrairieDrifter

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Parking brake cable deleted as well.
 

Redfish

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It's possible that one of the "new" components is bad.

I am curious about why it is "obvious" it's not the proportionating valve?

Are you 100% sure that the brake pedal is releasing the master cylinder completely?
 

rusted nuts

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84 k10 suburban. 75ish 12 bolt rear. New brake shoes drums and hardware, wheel cylinders. New master cylinder, the axle hard lines. Soft lines replaced a few years ago with ORD braided lines. the axle has new outer bearings seals and new axle shafts. Almost everything is new.

I've been chasing a brake drag problem. I just can't figure it out. Hardly noticeable till they get real hot, then once real hot they start squeaking, first with light braking, then after sitting at a light or something it'll start almost constantly squeaking and then fully at lower speeds, after enough time driving. Barely noticeable in rpm's, but noticeable.

The drivers side gets hotter, and hotter faster. Which is really throwing me through a loop, doesn't make sense. I've used some old drums and it seemed better at first but now they're adjusted where they want, the old drum is hotter than the other side where I have a new drum that has ALSO been cut down(also confusing). I tried another brand of new drum I believe and I had the same issue right away.

The brakes feel great! They seem to be balanced properly, once the rear shoes are adjusted properly. The rears don't lock up. I can't adjust the shoes off anymore without the pedal suffering, and then it self adjusts back to where it needs to be by itself anyways.

It's pretty obvious it's not a proportioning valve, its acting the same with the new master as with the old. Bleeding brakes was flawless, great flow, little air, definitely not a clogged or collapsed line.

I even thought the axles po had the wrong size brakes for the backing plate. So I tried the 11x2's but they didn't fit right even close. But from my research, these are indeed the big brake backing plates. So the brake size is correct.

Does the 75 ish axle not mix with the 84 master??

I thought maybe the old master was somehow transferring fluid to the rears, and keeping the brakes on, but that's definitely not happening. If the prop valve was the issue I wouldnt have front brakes, if the rears are getting hot. I have front brakes.

Also I know I have good brakes, they stop my 35's just fine. I could try a couple more brands of drums or shoes. But I'm so tired of it, and spending money on shelf parts, or returns.

IM ABOUT TO LOSE MY MIND. I'm about to drop a grand on a disc brake kit. And I really don't want to, not only the money, but the horror stories and mixed reviews.
Just cause You have GOOD flow from MC to brakes,,, don't mean You have good flow BACK to mc after You release them. You can have good flow ONE way thur a brake hose and have it blocked when it need to release the brakes.
 

Turbo4whl

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Is the squeak definitely from the back, or could it be from the front?
 

donnieray

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Just cause You have GOOD flow from MC to brakes,,, don't mean You have good flow BACK to mc after You release them. You can have good flow ONE way thur a brake hose and have it blocked when it need to release the brakes.
Very true, I've had lines that were collapsed on the inside and acted like a check valve.
 

bucket

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Brake hoses from ORD and they aren't very old? Yeah, I highly highly doubt they are a restriction.

I've seen brake boosters cause a brake drag before. The more you drove it, the worse it got. The booster was evidently keeping light pressure against the master cylinder.
 

PrairieDrifter

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Is the squeak definitely from the back, or could it be from the front?
100% the back. Not a u-joint, 100% back brakes. Not there when cold, comes when brakes get real hot.
 
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PrairieDrifter

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It's possible that one of the "new" components is bad.

I am curious about why it is "obvious" it's not the proportionating valve?

Are you 100% sure that the brake pedal is releasing the master cylinder completely?
I am almost positive it is, I have a nice floppy pedal at rest, a couple hairs of free play. It's definitely not the master, it acted the exact same. I've changed nothing else but shoes and pads recently, everything else is 1 year to 3 years old.

I think the new parts are the problem like drum or shoes, but Ive tried multiple and don't know what to do.

The proportioning valve cuts off flow to one section of brakes when it feels a loss of pressure. I haven't had a loss of pressure at the front since I've had the problem, we'll ever for that matter, as well as I have great working brakes. Maybe it could be slightly off, but no brake light and I never had a leak on the fronts.
 

PrairieDrifter

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Just cause You have GOOD flow from MC to brakes,,, don't mean You have good flow BACK to mc after You release them. You can have good flow ONE way thur a brake hose and have it blocked when it need to release the brakes.
I realize this, I just have all new brake lines that are 4ish years old, braided lines from ORD. My fluid has been crystal clear since I've worked on it. I've never had a problem bleeding. I just can't be convinced it's a collapsed hose.

As well as, the drivers side and passenger side are always different temps. I realize that could be adjustment from side to side, but they never really "even up"
 

PrairieDrifter

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Brake hoses from ORD and they aren't very old? Yeah, I highly highly doubt they are a restriction.

I've seen brake boosters cause a brake drag before. The more you drove it, the worse it got. The booster was evidently keeping light pressure against the master cylinder.
I don't believe it's hoses either. I suspected this but at all times it seems I have a perfectly fine floppy pedal all the way at rest, I can lift it and it feels like the rod comes off the master.

The real problem is I had never replaced brakes on my old axle till I got this 12 bolt. So I don't believe I had this issue with the other axles, well not for sure, but one of em for sure wasnt doing nothing with the huge greasy mess.
 
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Goldie Driver

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Wild guess - something like this that is keeping the shoes slightly engaged?

 

PrairieDrifter

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Also it would take a real like 30 mile drive to get em hot hot, but now it's less than 10
 

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