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2006 Suburban front brakes locked after transmission change?

Scott Nelson

By Scott Nelson
in Ask A GM Technician

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Scott Nelson New Member

Scott Nelson

Posted
Posted

I have 2006 Chevrolet Suburban, 1500, Z71, 5.3L. It recently lost "Drive" int he transmission, it would move if you manually shifted it down into 1st and shifted manually to 2 and 3rd, but nothing in "Drive". So we brought it to a transmission repair shop and had the tranmission replaced. (4L60E)

Now the problem is that the shop that changed the transmission now says that the front brake calipers are completely locked up and it can't even be test driven? We drove it there, and had driven it to another shop for an estimate before bringing it to this shop, but now somehow the calipers are completely locked up and they want $500 to repair the brakes?

 

What could have happend when they change the transmission to cause this issue?

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

If it cannot be test driven because the brakes are locked up, your truck must still be in the shop.  There is no connection between the brakes and the transmission.  Go have them show you how the wheels cannot be turned, as well as show you what part is locked up.  If the calipers are indeed locked up, and the brake rotors are discoloured from the excessive heat seized calipers would have created, then it is likely they were indeed seized.  Something to look for in the rotors are the cooling fins between the two friction surfaces of the rotors.  Normal drive over thousands of miles in all kinds of weather will create rust in those vents.  The older the rotors, the more rust it will have.  Not uncommon to have heavy flaking rust in there.  If the brakes have been locked on or dragging excessively, you will find there is no rust on those fins.  The extreme heat will cause the rust be cooked off.  The fins will look thinner than normal, and will have a textured appearance like they have been sandblasted.  The fins will still be rust coloured, just not actually rusty.  I would be asking why did they not notice this on the pre-repair test drive, or while the truck was on the hoist for the 4 to 8 hours it took to rebuild the transmission, assuming this is not a R&R shop that does not actually rebuild transmissions.  Even though it would be hard to believe that no one stopped to ask the mechanic a question and didn't smell the brakes.  The smell of burnt brake pads is pretty distinctive, or at least it used to be.

 

The odds of both calipers locking up at the same time are in the winning the lottery range.  Is your truck 2 or 4 wheel drive?  

Scott Nelson New Member

Scott Nelson

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  • Author
Posted

Thanks for your reply, It is a 4 wheel drive. It is and exchange shop, they are suppsoed to have installed a factory rebuilt transmission. They have had it for 10 days total so far.

Sorry, I was unclear in my post, I should have said that the test drive could not be completed. They adivsed that they only went 3 blocks and the front end started smoking, they stopped and determined that the brakes were "locked up".

After they got it back to the shop (not sure if they drove it or towed it), they inspected the brakes and say that pads are now "white" from the heat and that the calipers are "locked up".

Now they want to install new calipers, rotors and pads at "cost", to correct the problem.

I don't think that the calipers are the problem, but more the symptom and installing new ones will just wreck those as well. I am wondering if something is causing the ABS module to engage the front brakes? From what I have read the transmission control module, engine control module and ABS module all work together.

For them to start "smoking" in just 3 blocks it seems like the brakes would have to be putting on enormous amounts of pressure, not just stuck or locked up?

 

davester Senior Enthusiast

davester

Posted
Posted

The abs module doesn't apply the brakes, it just pulses the brake pressure.  It depends on someone stepping on the brake pedal to work.

 

I would suggest seeing if the brakes release if you open the drain valves on the calipers (ie, release the pressure).  If so, it points to a problem elsewhere, such as the brake hoses failing, or the master cylinder.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Have them check to see if the brakes are still locked up now that it has been sitting for 10 days.  You may have something very similar to another poster recently.  If the calipers are free now, and are behaving as expected, take it for a drive, if you are close to home, take it home, and see if they get hot again.  If they get progressively hotter the farther you go, and eventually stop the truck or begin to act like you know they are on, stop, turn the wheels all the way in one direction and using that 10mm wrench I forgot to mention, open the bleeder screw on the caliper that you can see with the wheels turned.  If you get a spurt of fluid out of the bleeder, tighten it back up(no need to really it down, just turn it until it stops with light pressure and then go another 1/8 turn at the most.  If the wheels are now free again you have an issue very likely with the compensating port being blocked when you foot is off the brake pedal.  This port must not be blocked because it is how the fluid gets returned to the master cylinder when it expands from heat.  If the port is blocked the expanding brake fluid will apply the brakes on the front wheels causing more heat, causing more pressure, etc.  

There is also the possibility of the flex hoses starting to fail internally and acting like a flapper valve, causing the brake fluid to stay in the caliper.  I have heard this suggestion many times, but in my experiences I have never seen this or heard first hand of anyone I know seeing this.  Personally, I have seen the compensating port being blocked many times.  Try opening the bleeder when the calipers are locked on and HOT.

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