Rear brakes locking up.

[The_Hammer]

This is on a 96' 2500 12v 4x4 auto. I replaced the rear brake shoes, drums, upgraded to GM cylinders and flushed the system. Front brakes are in excellent condition. Everything has been working fine until about a week ago. The rear brakes are really grabby and will lock up easily until the ABS system kicks in. I haven't had a chance to pull the drums yet but there are no visible leakes and everything looks ok. Could the proportion valve have crapped the bed?

Edited March 2, 2016 by The_Hammer

[Me78569]

Anyone else finding irony in the OP's avatar and now having brake issues?

 

 

 

just thought it was funny,  

I suppose the valve may have, but really no point in jumping to conclusions until you get the drums off.

[The_Hammer]

That was this past summer during the flood, I was hauling suplies back to my house  The brakes were replaced a couple months ago so I know that wasn't the cause.

[Hawkez]

My rear brakes are really grabby as well.  I only notice it at real slow speeds and before things have warmed up.

[dripley]

I dont even know what my rear brakes are doing. I changed the oe's out at near 300k and they still had pad left on them. The backing plates were rusting out and I figured it was time.

As far as the Hammer's problem I dont know.

[The_Hammer]

They do it at low speed regardless of temperature.

[Buzzinhalfdozen]

It's possible the proportioning valve is acting up. Have you checked if the rod from axle to valve is still there? Maybe some crud got in it when you flushed the brakes?

[dodgedieselnewbie]

Can't help.. but I had the proportioning valve deleted/bypass when the new rear brakes and GM cylinders were done a month ago. They are a little grabby but prefer that over next to nothing.  

Edited March 2, 2016 by dodgedieselnewbie

[The_Hammer]

16 hours ago, Buzzinhalfdozen said:

It's possible the proportioning valve is acting up. Have you checked if the rod from axle to valve is still there? Maybe some crud got in it when you flushed the brakes?

Everything was working fine up until about a week ago and I had replaced everything and flushed the system months ago. I smooth forgot to check the rod, thanks. 

[KATOOM]

The rear drums on these trucks are notorious for being a tad grabby during the first few touches of the brake pedal on wet or humid days.  Sometimes just making sure they're adjusted correctly will help with any grabby brake attitudes.

Also make sure you engage the e-brake when sometimes rolling backwards.  I do this every once in awhile and I can even hear the star wheel ratchet a click if it ever needs to move (they dont move often).  Stuck, rusted, seized star adjusters are VERY common so the rears eventually stop pulling their weight over time and then all you have is the front discs getting hot and wearing out fast.  And.....then resulting in threads about people complaining because their 2nd gen trucks dont have good brakes.

But as for grabbing really hard or severe lock up issues all the time..... Thats usually a sign of leaking axle seals or leaking brake cylinders contaminating the shoes.  A faulty proportioning valve can also cause either axle to pull more load than it should be, meaning the rear brakes power is reduced as the truck sits higher or have more power as it sits lower.

[The_Hammer]

Found the issue. In my rush to get the brakes back on during a rain storm with nothing but an open sided carport for shelter, it seems that I didn't properly install the parking brake lever on the driver's side brake shoes. It wasn't located in the slot on the rear shoe and had become wedged at angle. On the passenger's side I found the star wheel had froze up. Once everything was straightened out my brakes went back to working as they should.