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GT-350 Rear Drums

Started by oldcanuck, February 03, 2025, 08:52:46 AM

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oldcanuck

Noticed a slight drip on the left rear inside tire.

After disassembly it appears one side of my brake cylinder is the source.

My questions are;

Can I remove the wheel cylinder without disassembling the whole brake shoe(s) assembly ? It is a little tight in there.....

Are the wheel cylinders on a late '67 7/8" or 15/16" ?

Thanks in advance for any assistance.

Bob
Bob
Knoxvegas, TN

shelbydoug

Quote from: oldcanuck on February 03, 2025, 08:52:46 AMNoticed a slight drip on the left rear inside tire.

After disassembly it appears one side of my brake cylinder is the source.

My questions are;

Can I remove the wheel cylinder without disassembling the whole brake shoe(s) assembly ? It is a little tight in there.....

Are the wheel cylinders on a late '67 7/8" or 15/16" ?

Thanks in advance for any assistance.

Bob

No. The cylinder is "on the bottom of the pile". Everything assembles to it, or on top of it. You do it all from the outside of the fender except for the mounting and connection to the brake fluid line. That you can also do from the outside by reaching over and behind but your head will be within the fender.
68 GT350 Lives Matter!

greekz

Quote from: shelbydoug on February 03, 2025, 09:40:56 AM
Quote from: oldcanuck on February 03, 2025, 08:52:46 AMNoticed a slight drip on the left rear inside tire.

After disassembly it appears one side of my brake cylinder is the source.

My questions are;

Can I remove the wheel cylinder without disassembling the whole brake shoe(s) assembly ? It is a little tight in there.....

Are the wheel cylinders on a late '67 7/8" or 15/16" ?

Thanks in advance for any assistance.

Bob

No. The cylinder is "on the bottom of the pile". Everything assembles to it, or on top of it. You do it all from the outside of the fender except for the mounting and connection to the brake fluid line. That you can also do from the outside by reaching over and behind but your head will be within the fender.

Agree, also you might consider doing the right side as well so you have a matched set of new cylinders for even braking. A perfect opportunity to inspect brakes shoes and lubricate the raised pads on the backing plate where the edge of the shoes ride.  I use lubri-plate.

Not sure of which size cylinder.
SFM 6S1134  '67 GT-350 #2339

KR500

Bob
Yes you can remove the wheel cylinder without removing the brake shoes although it is slightly easier with them removed and with a few simple brake tools it is easy to remove them. To remove them with out removing the brake shoes remove the primary and secondary brake shoe retaining springs and self adjuster cable. This is required for the fronts but optional on the rear if the parking brake equalizer bars are still being used. On the rear the parking brake equalizer bar will keep brake shoes spread apart so it is not necessary to remove any brake shoe retaining parts.For the rear wheel cylinder replacement. Remove the tire and brake drum. Clamp the rear brake hose off. Remove the brake line nut from the wheel cylinder. Compress the wheel cylinder pins and pistons to remove the brake shoe pins. Remove the 2 wheel cylinder retaining bolts and remove the wheel cylinder, you may need to pry or smack the cylinder with a hammer to break it loose from the baking plate. Clean the leaked fluid from the backing plate and brake hardware. If the brake shoes are contaminated with fluid replace them. I find that if one wheel cylinder is bad on an axle the other is not far behind and it is wise to replace them both. Also it is wise to replace the brake fluid as this may be the reason the wheel cylinder failed in the first place. Unless you are using a DOT 5 silicone fluid, DOT 3 & 4 fluids are hydroscopic, they absorb moisture. Honda and a few other OEM's recommend a brake fluid replacement every 3 years. Do not forget that brake fluid ( DOT 3/4 will eat your paint ). Check to make sure it is not the axle seal that is leaking also. Replace the wheel cylinder(s) in reverse order and bleed the brakes.
Rodney 
Rodney Harrold,Ohio SAAC Rep,SAAC 68 Shelby Concourse Judge,68 GT500KR 02267

oldcanuck

Rodney,

Thank you.... wheel cylinder is already loose as I have undone and capped the brake fluid line and removed both retaining bolts.

How best to compress the cylinder pins as I think I can wiggle it out past both return springs from there....?

Bob
Bob
Knoxvegas, TN

Road Reptile

Hi,
Just to add a few key points. This is a simple job when done with the proper tools.
If you do not have tools maybe borrow or buy them from Harbor Freight....Be careful and wear safety goggles or eye protection-you are working around springs that can quickly damage your eyes. Do not just repair 1 side!!!! This is asking for trouble when driving and if 1 side is worn out/leaking the other side is most likely not much better.
Ford used larger wheel cylinders which is necessary with the wider brake shoes. If memory serves they are 29/32" This is not listed for any "Mustang" application.As mentioned all parts should be inspected-cleaned-lubricated prior to assembly. Remember this is crutial to get working properly...rear wheel lockup can also happen with shoes that are contaminated....so inspect carefully. Good luck.
R.R.

Bob Gaines

Quote from: Road Reptile on February 03, 2025, 10:24:48 AMHi,
Just to add a few key points. This is a simple job when done with the proper tools.
If you do not have tools maybe borrow or buy them from Harbor Freight....Be careful and wear safety goggles or eye protection-you are working around springs that can quickly damage your eyes. Do not just repair 1 side!!!! This is asking for trouble when driving and if 1 side is worn out/leaking the other side is most likely not much better.
Ford used larger wheel cylinders which is necessary with the wider brake shoes. If memory serves they are 29/32" This is not listed for any "Mustang" application.As mentioned all parts should be inspected-cleaned-lubricated prior to assembly. Remember this is crutial to get working properly...rear wheel lockup can also happen with shoes that are contaminated....so inspect carefully. Good luck.
R.R.
I wanted to add that although 29/32 was what the factory used with the 2 1/2 inch rear shoes that size can be hard to find and many times a overseas metric equivalent is substituted in its place which although quoted as 29/32 the metric equivalent is different.This is another reason to replace both wheel cylinders so that they both match. Yes we are kept in the dark about many of these metric substitutions buyer beware.  15/16 is the next best alternative if you can't find the 29/32. 
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

roddster

If you can determine the wheel cylinder(s) are original by it having a small bleeder valve I suggest you send the cylinder out to have it sleeved. Hard to find the small bleeder valve ones that look original. If this matters.

Bob Gaines

Quote from: roddster on February 03, 2025, 10:53:49 AMIf you can determine the wheel cylinder(s) are original by it having a small bleeder valve I suggest you send the cylinder out to have it sleeved. Hard to find the small bleeder valve ones that look original. If this matters.
Of course check the internal diameter to determine if original. The 1/4 bleeder although a good sign that it may be original is not a absolute as many were replaced on cars before the cylinders evolved to the larger bleeder in later years.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

KR500

#9
Quote from: oldcanuck on February 03, 2025, 10:21:04 AMRodney,

Thank you.... wheel cylinder is already loose as I have undone and capped the brake fluid line and removed both retaining bolts.

How best to compress the cylinder pins as I think I can wiggle it out past both return springs from there....?

Bob
Fingers if not frozen or stuck hard. Screwdriver, punch or pry bar if frozen. Compressing the pistons in the bore will shoot fluid out the line opening in the back so put a rag or towel to catch the fluid.
Rodney Harrold,Ohio SAAC Rep,SAAC 68 Shelby Concourse Judge,68 GT500KR 02267

T-Bone68

Is it worth Bob calling Chris Brown's Browns Auto Body service and ask if they have any more?  I believe they sold 15/16in, but with a more correct 1/4 bleeder. I know they are out of the business since his passing, but maybe some left over?

Bob Gaines

Quote from: T-Bone68 on February 04, 2025, 09:16:43 AMIs it worth Bob calling Chris Brown's Browns Auto Body service and ask if they have any more?  I believe they sold 15/16in, but with a more correct 1/4 bleeder. I know they are out of the business since his passing, but maybe some left over?
All of the old inventory was sold recently (last 6 months). George Huisman of Classic Design Concepts bought it all and has been wholesaling it to various vendors . You might call NPD and ask if they bought any of that.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

azdriver

Try West Coast Classic Cougar. They might still have some 7/8" ones..

Pat

s2ms

Dave - 6S1757

oldcanuck

Guys,

Thank you for all the assistance. After removal it was only a small drip from one side. After disassembly, and cleaning there was no scoring or corrosion, just a small piece of something on one of the seals. Everything was pliable, no swelling and pistons were clean and smooth. So I went ahead and cleaned it all up and reassembled. Took it for a short hop this afternoon and all seems well.

Thanks again for all your expertise......
Bob
Knoxvegas, TN