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How to identify correct rear drum brakes?
#1
Hi All,
Working on the rear brakes on my 71 Sportroof. Car was originally a 302-2V with a 3 speed manual and 8" rear. Rear axle was converted to a 9" from a 69 Cougar, but the rear backing plates from the 8" were changed over to the 9". Did this with a sealed system as I had already replaced the rear shoes and cylinders and didn't want to open everything up again.

I replaced rear shoes when I first got the car and do not remember being asked what width I needed, was handed a box and installed them. They are currently 1-3/4" wide.

The drums the car had when I got it were hosed and were exchanged for the drums from the 9" rear end, which I found today are 2" wide. These were perfect but had some deformation of the center portion from pulling them, so there was a little wobble when rotating. I went to replace them with new and was told I needed to know the width, which at that time I didn't know.

Fast forward several years where the car has been mostly parked and I am now driving it. I have found that I have a great issue with the rear brakes locking up on gentle stops, never mind panic stops. Pulled the drums today and found no leaks at the cylinders, very good looking linings, rubbing of the drum on the backing plate on the side that locks (maybe locking due to out of round/true condition of the drum?) and some broken hardware on the side opposite of the locking wheel.

I want to start completely new with the rear brakes so as to eliminate any questions with that end of the system.

The PO was a non-mechanic so my paying more attention when I first got the car might have helped, but I have learned that he often did things more wrong that I could, even with me being a GM guy. And he had been all over the brake system, with almost disastrous results.

1 Should I should have 1-3/4" linings and drums or the 2" parts on my car?
2 Are the backing plates specific to the brake width?
3 If so, how can I identify what backing plates I have?
4 is there any way to mod the backing plates/hold downs so I can run 2" parts on 1-3/4" backing plates?

Thank you for any input,
Tom
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#2
The 1971 Ford shop manual lists 10 x 2.00 for the rear (302). 1.75 for 1969 Cougar (302). Assuming OEM backing plate and drum design, I'd think the wider drum would touch the edge of the backing plate before it seated on the axle flange. The edge of the backing plate is supposed to run in a groove cast into the outer edge of the drum. Replacement drums may be cast to accommodate various width to reduce the number of casting to cover a range of vehicles/engine sizes. I don't if the picture will help any but, here it is. Chuck


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#3
Hello Chuck,

Thank you for the info and pic. I <think> the rear axle in my car was original, and therefore the backing plates should be original and for 2" wide brakes, but will use your picture to try to help ID them more positively. If all looks good, I will be securing a pile of 2" parts to try to sort out the rear brake lock-up issue.

The wheel cylinders look like I would expect from some that are not leaking or weeping. The dust inside the drum and on the hardware was a powder, didn't look wet, but looked damp maybe? As I said, no glistening wetness from the cylinders, but should I replace on "while I'm here" principles? Or wait and see if the new drums, shoes, and hardware eliminates the locking?

Thnak you,
Tom
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#4
Given what you have said about the previous owner's lack of ability and having been all over the brake system, I'd suggest getting a set of ford shop manuals and using volume one, section 12 to verify everything is properly installed and adjusted. Was it very hard to remove the drum on the side that locks up and the other side not? The adjusters could be reversed left to right. That is just a WAG. I've even seen a person reverse the front and rear lines at the master cylinder, it took a lot of effort but, they did it. If you keep the car, the manuals will pay for themselves many times over. Let us know what you find. Chuck
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#5
Hi Chuck,
I have the manuals, put it all together using them when I first got the car, as I am not 100% close-my-eyes conversant with Ford brakes. Never noted the info on diam vs shoe width tho, is that where you found that?

The drum that would lock and that was rubbing the backing plate was the drivers, and came of very easily. All hardware was intact. The passenger drum, which I had to pull using a big gear puller (was stuck on the hub center), was a little tight on the shoes after it popped off of the hub, and the upper rear spring was broken with the cable guide down at the bottom wedged between the shoes under the adjuster screw. Guide is done but the drum has a minor groove, so may have happened recently. Going to replace both drums and ALL hardware inside. Once I tear it down I will decide on shoes and cylinders, but those look fairly good. Could the broken spring/adjuster have prevented the right brake from working allowing all the work to happen of the left?

I will check the adjusters for being on the correct side, but I imagine they are, as they were not when I first got the car and they then were corrected. Also, the shoes were not correctly set up either, 2 longs on one side and 2 shorts on the other. Fixed that too.

Musta been interesting to drive for the PO
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#6
roadwarrior;184509 Wrote:Hi Chuck,
I have the manuals, put it all together using them when I first got the car, as I am not 100% close-my-eyes conversant with Ford brakes. Never noted the info on diam vs shoe width tho, is that where you found that?

The drum that would lock and that was rubbing the backing plate was the drivers, and came of very easily. All hardware was intact. The passenger drum, which I had to pull using a big gear puller (was stuck on the hub center), was a little tight on the shoes after it popped off of the hub, and the upper rear spring was broken with the cable guide down at the bottom wedged between the shoes under the adjuster screw. Guide is done but the drum has a minor groove, so may have happened recently. Going to replace both drums and ALL hardware inside. Once I tear it down I will decide on shoes and cylinders, but those look fairly good. Could the broken spring/adjuster have prevented the right brake from working allowing all the work to happen of the left?

I will check the adjusters for being on the correct side, but I imagine they are, as they were not when I first got the car and they then were corrected. Also, the shoes were not correctly set up either, 2 longs on one side and 2 shorts on the other. Fixed that too.

Musta been interesting to drive for the PO
I believe it is at the end of the section as "specifications". What you describe would account for one side not working. Whether or not that caused the other side to lock-up is hard to say. I suppose it is possible. Your approach of checking everything and replacing all the hardware is a good one. Please let me know the results after you get it back together. Chuck
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#7
Chuck,
Will do, ordered a pile of stuff yesterday for this, should have everything by the weekend. If I get the parts and have the time, everything will go back together soon. I will update after assembly and testing.
Tom
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#8
OK, after getting all of the shoes and springs installed, replacing the rear wheel cylinders and rear hose, and finally getting the rear drums that I had ordered. put the car on the ground and all seems good. Pushed the brakes harder than I do in normal driving and not even a sensation of locking.

However I now am hearing noises in the front suspension, which was rebuilt many years/very few miles ago.

The fun never ends does it?

Thank you to Chuck for the input, I will update if anything changes.
Tom
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#9
I'm glad it worked out with the brakes. If the noise in the front is a squeak, it could be a dry upper control arm bushing. Let me know if I can help. Chuck
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#10
Hi Chuck,

No, heavy clunk, like a loose strut rod bushing or upper control arm mount. No squeaks.

All arms, spring seats, and strut rod bushings were replaced with new over 15 years ago after I first got the car and have very few (<1k?) miles on them. Just need to sleuth it out. I will post up any questions in a new thread depending on what I find.

at least the brakes are good!

Tom
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