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2500 Avalanche rear disc brakes issues

CarMech1969

Full Member
Joined
Jul 1, 2016
Messages
498
Location
Scarborough, ON
Hello there CAFCNA folks!  :B:

Anyone here ever had rear disc brake problems? I bet more than a few.

Mine went bad on the way home from a fishing trip.

Had the boat in tow, and when we were almost home, it seemed as if I had started to do a tractor pull.

Anyways, to make a long story short, when I got home and hopped out to investigate, the rear brakes were really hot.

I tore them down over the weekend, and discovered that the caliper pistons were sticking in their bores.

Got some rebuilt calipers and new brake pads, and everything is fine again.

The thing that I didn't notice right away is this:

Why did GM design the rear brakes with the caliper in FRONT of the axle, where it can catch all the mud, water, road salt, and all that crap??

On the front axle, the calipers are mounted BEHIND the axle.

What the heck is that about?

A Google search will show loads of issues with this vintage and style of rear brakes.

Surely the engineers could simply have mounted the calipers aft of the axle, which would have made more sense, since the axle would serve to shroud the calipers somewhat.

What you all reckon? I'm just thinking GM could have done better.

CarMech1969
 
I don't think front or back would make that much of a difference to how much junk would be picked up by the caliper.
 
Rear Calipers sticking on GM vehicles is a common occurrence for all models that have 4 wheel disc brakes.

Biggest issues causing this is lack of proper caliper slide grease on slide pins and/or torn boots.

I have read that flushing the brake fluid can also help since your brake fluid is like a sponge and collects all sort of moisture and debris from the system. Which is weird since it is a sealed system.

With my '94 vintage caprice it was common for people that raced them to use Synthetic fluid that has a MUCH higher temperature that it breaks down at which allows better performance but is MUCH more sensitive to moisture in the lines. Believe we used Valvoline Synthetic but it was suggested to change it every year.

Also should mention that flushing the brake fluid tends to keep the ABS module alive longer as well.
 
It does not matter if it's in the front or rear of the axle, it's the same environment.

BTW the rear caliper on the 2500 is the same one that is on the front on the 1500.


One of the reasons why that crud is in the caliper is because some folks do not open the bleed valve when the push back the piston. If they do that to the fronts they push it back into the abs module.

 
its a known issue.... newer trucks have em behind rear axle
 

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I remember a thread years ago about this idea, I don't remember if it was here or diesel place. Jimbo is my guy for everything 2500 or mod to make mine a tow beast, but I still don't buy the idea.

Jimbo don't hate me I still need your help sooner or later.  I would say that is a mightly fine rearend in the picture but it would not sound right. BTW the search is on  for a 3500 De?ali but the AV is still staying mine.  (y)
 
JUnk and debris on the outside should not effect the piston getting stuck on the inside since it is protected....

And how does it being in the front make it catch more crap if it was on the rear or say the top or the bottom?

Calipers are inside the wheel so the wheel protects it only way stuff gets to caliper is through the sides...

Example would be driving into a mud pit... then all the mud could get to calipers when you go slow....as it would pour in from side... but go fast enough and the tires blow the mud away to the sides and calipers stay clean.
 
Never had a problem with the  rear calipers on my 2500.

In fact I had bought new front and rear rotors when I upgraded the the front calipers to the SSB 3 piston Aluminum at about 45,000 miles thinking the rear pads would need to be changed soon but they didn't. Then every 40,000 -45,000 miles after that the front would need new pads but the rear would not. Then at about 160,000 miles they still had about half the pad left, I went ahead and changed them and put new pads on even though they still had some life left.
 
When I did mine at around 105K the rotors were severely pitted both front and rear

The pads in the rear were shot and the fronts were half used up. Next time I'm going with hummer rotors in front which are a bit bigger since I don't have the 16 inch wheels any longer. I going to see if I can get them to work harder. I think the problem was where I lived(michigan)

You should have seen the crud that came out of the calipers. 
 
Yea, weather defiantly will cause problems..

Living in California has it's advantages when it comes to vehicle longevity...
 
trying to find tsb....


Date Reported:
JUNE 01, 2004

NHTSA Reference:
#10012141

TSB Reference:
#040523005


Description: AVAILABILITY OF REAR WHEEL MUD FLAPS TO REDUCE DEBRIS BUILD-UP ON REAR BRAKE CALIPERS AND/OR REAR WHEELS
 
I found that one, but how would a rear mudflap stop a buildup on the rear caliper wouldn't it cause more problems because the debris will be trapped behind it. Now every 4 wheel disc vehicle I every owned had the problem, because I lived in the wonderful state of Michigan where our state flower is orange barrels. The road construction debris is a really bad problem.

After I read this thread I thought I'd take a look at my rotor and found this 2 grooves
 

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I guess I'm going to have to go look at my now... They have about 85k o them...
 
Thanks everyone for the feedback.

I'm thinking that when guys just do a pad slap, and never open the bleeders (as what redheadedrod and MS03 2500 mentioned), the moisture that accumulates in the brake fluid could conceivably cause damage to the piston bores - that does make sense.

Makes me wish I had flushed the front brake calipers when I had the wheels off to check the caliper slide pins and pad guides.

The slide pins were fine, but the pad guides were pretty crusty. I took the caliper brackets off and cleaned them up, put on some better pad guides (spring clip, whatever it's called) that I had kicking around, and used antiseize lube on the pad contact points so that the pads would float properly. Seems pretty good. I bet front flex hose replacement is in the not-too-distant future, as they look pretty crusty too.

Time will tell!

CarMech1969
 
Russel makes a good hose kit..

PN 672440 are the ones I have on mine. They say they are for non-lifted but it depends on the lift. My lift did not require longer hoses, I have a 6" lift and they work fine.  PN 695770 if you need longer hoses..

About $100 at Summit..

https://www.summitracing.com/parts/rus-672440

https://www.summitracing.com/parts/rus-695770
 

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