1999 tahoe 4×4 brake trouble

[R422b]

Howdy all.
I am new here and just learning how to post on forums so please help me out if i am in the wrong section.

I have a 1999 chevy tahoe 5.7 4×4 270000 miles that is having some brake troubles.

Symptoms: at some temperatures (around 40* to 60*) the rear brakes lock suddenly when aplied at low speeds and have excessively strong initial bite at higher speeds but if it is very cold (approximately 35* or less) or warm enough ( much over 60*) then they act somewhat normaly.
Also at any temperature they have a bit of pulsation but not felt in the pedal.

 

[R422b]

Stock tire size is 245/75r16 and the curent tires are 265/75r16 cooper discoverer atp on the front and bfgoodrich all-terain t/a ko2
Also the abs apears to be non operational, if i remember clearly the computer sed it lost comunication with abs system or something to that effect.
So i am wondering if youall can help me determine the cause of the brake troubles.
I am leaning toward thinking that i have brake fluid contamination on the rear drum shoes.
What do youall think?

 

[94burbk1500]

Check your wheel cylinders for leaks.

 

[R422b]

I will try and get some time this weekend.
Also can drums warp? I am drum illiterate.

 

[R422b]

Well no time so far. I got sick and it is freezing here literally.
But i did talk to the last guy that worked on it and he sed he thinks the backing plate is worn in such a way that the edge of the shoe is falling into a groov or something and grabbing when the brakes are applied.
I dont really understand that explanation and it doesent seem to explain the tempersture dependance to me.
Any thoughts?

 

[east302]

You’d need to take the drums off to look at the backing plates. There are spots where the edges of the shoes rest that can get worn. They’ll usually have little grooves from normal wear, but if they get too deep the shoes can stick. The repair is either new backing plates or filling the grooves in with a weld and grinding it smooth.

Drums can become out of round, that can cause a hopping or pulsing sensation different than what you feel in the pedal with a rotor issue.

You just need to open it up and see what it looks like. As someone said above, a leaking axle seal or wheel cylinder can contaminate and cause issues. The leak would be pretty obvious, everything would be oily/wet.

Check YouTube for videos on replacing drums if you’re not familiar with them. 1AAuto has some good walk-throughs. Depending on your drum size, there are two different styles. Check the RPO label, it will be either JB5 or JB6.


Sent from my iPhone using Tapatalk

 

[R422b]

Thanks for taking the time to reply east302 that all makes sense. I really need to get some time and pull one side off. With warped drums is it a catch and release feeling?

 

[east302]

When I’ve had out of round drums, it almost felt like a hopping feeling in the back under moderate braking from, say, 50 down to 30 mph or so. Once it dropped below that, it was fine on down to zero.

If it feels like it’s sticking, then it sounds more like a shoe issue, the backing plate being a good place to start but it could just be a damaged spring or something.


Sent from my iPhone using Tapatalk

 

[R422b]

Ok interesting.
This one grabs at low speed. Going through a parking lot when someone walks in front of me and i have to press the brakes a bit quicker than usual but still not a panic stop it feels like nothing for the first bit of petal travel and then the rear lock suddenly and screech.

 

[R422b]

Ok so i got a few minutes and yanked the pasenger side off and all looks well.
There are some groves but they dont look bad to me.
Here are the pics.
1st is pas side front shoe
2nd is close up of the grove at the top
3rd is closeup of the grove at the botom

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach