Rear Drum Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gmc67swb · 10-10-2003, 05:39 PM

I WAS DOING MY BRAKES TODAY. I BOUGHT A SET OF REAR DRUMS BEFORE STARTING, ONLY TO FIND THAT THEY WOULD NOT FIT CORRECTLY. I TRIED SEVERAL PARTS STORES ONLY TO SEE THE SAME DRUM BRAKE FOR MY TRUCK (THAT DIDN'T FIT) THE ONLY DIFFERENCE BETWEEN THE TWO IS THE MOUNTING SURFACE ON THE EXISTING DRUM IS FURTHER OUT ALLOWING THE DRUM TO GO ALL THE WAY TO THE BACKING PLATE. THE REPLACEMENT UNIT WOULD NOT MAKE IT TO THE BACKING PLATE. HAS ANYONE HAD THIS ISSUE AND IF SO WHERE DID YOU GET YOUR DRUMS.

THANX IN ADVANCE,

LARRY

Duallie · 10-10-2003, 05:53 PM

I don't know 1/2 tons well, but I seem to remember that Suburbans got the 2.5" drums while the trucks got 2" drums. And that may only apply to '73-up. Assuming you have a 1/2 ton.
What manner of axle do you have?

Southpa · 10-10-2003, 08:30 PM

I'm assuming thats your GMC in the avatar. The standard size for 67 1/2 ton (aka 910) is 11" inside dia. X 2" deep. The 3/4 ton (aka 920) rear drum is 11 5/32" X 2 3/4" for the stock GM rear axle. Compare dimensions w/ the old drums to make sure before you buy. I always check and verify the dimensions at the counter when I pick the part(s) up. These trucks been around for a while so who knows whats been done to them. Hell, you could even have a ford rearend,

j/k!

The 67 3/4 ton also came w/ Spicer rear axle which used 12 X 2 1/2" drums but no chance of mixing that up.

gmc67swb · 10-11-2003, 09:57 AM

THE ONES ON MY TRUCK ARE 11 X 2 AND THE ONES FROM THE PARTS STORE ARE ALSO 11 X 2. THE DIFFERENCE IS IF YOU LAY THEM FLAT ON THE GROUND THE ORIGINALS MOUNTING SURFACE IS TALLER SO IF YOU PUT THE REPLACEMENT ON IT DOESN'T REACH THE BACKING PLATE.

cwilli84 · 10-11-2003, 05:54 PM

Did you try Auto Zone. They had both sizes and they fit fine on my 69.

10-10-2003, 05:39 PM	#1
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	Rear Drum Question I WAS DOING MY BRAKES TODAY. I BOUGHT A SET OF REAR DRUMS BEFORE STARTING, ONLY TO FIND THAT THEY WOULD NOT FIT CORRECTLY. I TRIED SEVERAL PARTS STORES ONLY TO SEE THE SAME DRUM BRAKE FOR MY TRUCK (THAT DIDN'T FIT) THE ONLY DIFFERENCE BETWEEN THE TWO IS THE MOUNTING SURFACE ON THE EXISTING DRUM IS FURTHER OUT ALLOWING THE DRUM TO GO ALL THE WAY TO THE BACKING PLATE. THE REPLACEMENT UNIT WOULD NOT MAKE IT TO THE BACKING PLATE. HAS ANYONE HAD THIS ISSUE AND IF SO WHERE DID YOU GET YOUR DRUMS. THANX IN ADVANCE, LARRY __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

10-10-2003, 05:53 PM	#2
Duallie Registered User Join Date: Feb 2001 Location: Nikiski, Alaska Posts: 477	I don't know 1/2 tons well, but I seem to remember that Suburbans got the 2.5" drums while the trucks got 2" drums. And that may only apply to '73-up. Assuming you have a 1/2 ton. What manner of axle do you have? __________________ Just as if I knew what I was doin'

10-10-2003, 08:30 PM	#3
Southpa Registered User Join Date: May 2000 Location: Victoria, BC, Canada Posts: 2,410	I'm assuming thats your GMC in the avatar. The standard size for 67 1/2 ton (aka 910) is 11" inside dia. X 2" deep. The 3/4 ton (aka 920) rear drum is 11 5/32" X 2 3/4" for the stock GM rear axle. Compare dimensions w/ the old drums to make sure before you buy. I always check and verify the dimensions at the counter when I pick the part(s) up. These trucks been around for a while so who knows whats been done to them. Hell, you could even have a ford rearend, j/k! The 67 3/4 ton also came w/ Spicer rear axle which used 12 X 2 1/2" drums but no chance of mixing that up. __________________ 1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first. Last edited by Southpa; 10-10-2003 at 08:45 PM.

10-11-2003, 09:57 AM	#4
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	THE ONES ON MY TRUCK ARE 11 X 2 AND THE ONES FROM THE PARTS STORE ARE ALSO 11 X 2. THE DIFFERENCE IS IF YOU LAY THEM FLAT ON THE GROUND THE ORIGINALS MOUNTING SURFACE IS TALLER SO IF YOU PUT THE REPLACEMENT ON IT DOESN'T REACH THE BACKING PLATE. __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

10-11-2003, 05:54 PM	#5
cwilli84 1FINE69 Join Date: Aug 2003 Location: Detroit, Michigan Posts: 239	BRake drums Did you try Auto Zone. They had both sizes and they fit fine on my 69. __________________ Had a 69 swb fleetside 350zz3 w 400turbo trans oak lined bed with rhino coated sides red exterior. SOLD



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