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Author Topic: Rear Drum Brakes Popping??  (Read 1178 times)
79HeritageT/A
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« on: September 18, 2012, 02:38:11 PM »

Hi,

My brakes on my '79 are popping (almost like they are trying to set?) when in reverse and now a little bit in drive at slow speeds.  I have replaced the pads/rotors (front) and shoes and wheel cylinders (back) a few years ago.  I might have put about 500 miles on the car since but can't figure out why they would be making noise now.

Any help appreciated!

Thanks.
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Current Garage:

1979 Pontiac Trans Am (less than 24,000 original miles!)
2001 Chevrolet Silverado
2010 Chevrolet Malibu
LeighP
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« Reply #1 on: September 18, 2012, 03:39:53 PM »

Check the condition of the rear shoes for oil contamination.
what you describe are exactly the symptoms my 76 T/A had when the axle seal was leaking and the shoes were oil soaked.
I scrubbed the shoes with carby cleaner and wiped out the inside of the drum as well - after I replaced the axle seals and bearings (since I was already in there, bearings are cheap)....that saved the shoes.
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Regards,
Leigh

Sydney, Australia
Former Firebirds -
1971 Pontiac Firebird 455
1977 Pontiac Trans Am
1976 Pontiac Trans Am
1967 Pontiac Firebird 400 convertible
1967 Pontiac Firebird 400 coupe

Grand73Am
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« Reply #2 on: September 18, 2012, 10:11:12 PM »

Also, I'm wondering if the popping is really the rear brakes? Maybe it's the posi rearend making the noise? If you've never changed the rear end gear oil and put in new posi additive, the rearend can make those kinds of popping and chattering noises. Mine used to do that, and by putting in new gear oil and additive it quieted and smoothed out.
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Steve F.
79HeritageT/A
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« Reply #3 on: September 19, 2012, 12:06:01 PM »

Thanks for the tips LeighP and Grand73TA.  I hadn't thought of either of those.  It's in the shop today getting a new exhaust put on and an alignment done.  I'm having them check the brakes as well.  I'll certainly run your ideas past them.

I'll let you know what I find out.
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Current Garage:

1979 Pontiac Trans Am (less than 24,000 original miles!)
2001 Chevrolet Silverado
2010 Chevrolet Malibu
79HeritageT/A
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« Reply #4 on: September 20, 2012, 12:11:28 PM »

Well the T/A was in the shop yesterday for a new exhaust system and brake adjustment.  The back brakes did need to be adjusted but the mechanic said the popping was being caused by the differential.  He recommended replacing the fluid so that's next on the list.

The mufflers were bad which I knew but the pipes that were on it also looked like swiss cheese.  



It's been out of alignment since I purchased it in 2007 so I had them go ahead and do a full four wheel alignment on it as well.



It's ready to go to it's first show now.  Might hit up the Niftee Fifties show in Spring, TX this Saturday.

Thanks again for everyone's help and suggestions!
« Last Edit: September 20, 2012, 12:14:22 PM by 79HeritageT/A » Logged

Current Garage:

1979 Pontiac Trans Am (less than 24,000 original miles!)
2001 Chevrolet Silverado
2010 Chevrolet Malibu
LeighP
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« Reply #5 on: September 21, 2012, 04:02:09 AM »

That sort of noise from the differential could be a case of no LSD additive in the oil????? I've heard GM LSD differentials when they have the wrong oil in them...they complain loudly!  Laughing 
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Regards,
Leigh

Sydney, Australia
Former Firebirds -
1971 Pontiac Firebird 455
1977 Pontiac Trans Am
1976 Pontiac Trans Am
1967 Pontiac Firebird 400 convertible
1967 Pontiac Firebird 400 coupe

silver78
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« Reply #6 on: September 21, 2012, 06:08:19 AM »

I had the same poping noise only during turns.  I put the correct posi addidive in the rear diff and corrected it.  You will ruin the clutches in the posi if you run it too long making that noise.
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79HeritageT/A
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« Reply #7 on: October 15, 2012, 11:57:51 AM »

Thanks everyone for your suggestions!  I had the rear differential fluid changed Saturday morning and had the additive put in as well.  The noise seems to have gone away but I haven't driven but a few miles to have this done and back to the garage.  I'll be driving it further Wednesday though to have the exhaust fixed.  They put the tips up too high so they're going to fix it for me.
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Current Garage:

1979 Pontiac Trans Am (less than 24,000 original miles!)
2001 Chevrolet Silverado
2010 Chevrolet Malibu
LeighP
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« Reply #8 on: October 15, 2012, 03:06:39 PM »

Amazing how fast the noises go away with the right additive....seen that before on a friend's car.
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Regards,
Leigh

Sydney, Australia
Former Firebirds -
1971 Pontiac Firebird 455
1977 Pontiac Trans Am
1976 Pontiac Trans Am
1967 Pontiac Firebird 400 convertible
1967 Pontiac Firebird 400 coupe

Grand73Am
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« Reply #9 on: October 15, 2012, 07:02:15 PM »

Drive it to an empty parking lot and do a number of figure 8 turns. That will work the additive into the clutches faster and you'll notice improvement quicker.
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Steve F.
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