What's the difference between 1967 and 1969 rear drums? (do they interchange?)

[MoPar~Man]

In the past couple days I've been looking to see where I can get new rear drums for my '67 Dodge Monaco. Drums all around, rear shoes are 2.5". Rock auto shows a few PN's (Dynamic friction, centric) but no stock. I call around locally and I give them some rock auto PN's for front and rear drums - they see the front PN's in their system (but zero stock) but they don't see the rear PN's.

While on the line with a NAPA store, I asked them to look up rear '69 Monaco and a Napa premium PN turned up (4401168) which they have ($167 CAD each - yikes).

So my question is - what's the diff between '67 - '69 C-body rear drums? Both being for 2.5" shoes. Any axle differences here?

I'm going to look into having my existing rear drums turned / machined. I don't know if they're out of round or if they actually need any work.

What exactly would prevent a front drum from being used on the rear - aside from a 2.75 vs 2.5 shoe difference?

 

[CBODY67]

In the Rock Auto catalogs, if you click on the part number of the brand of item, it opens a smaller box with the model years and models that part can fit. If you click on the "INFO" icon, it brings up a new page with that parts information, specs, and OEM part numbers it crosses with. On that second page, if you click on the brand's logo in the upper lh corner, it takes you to that company's website and possibly THEIR catalogs, too. Really a pretty neat arrangement!

In the world of brake drums, the weight of the drum is tailored, generally, to the amount it heat it is designed to absorb. The surface finish can vary as to heat dissipation. Meaning a smooth exterior, a partially-finned exterior, or a finer-finned exterior as some '70s C-body car (mu '70 Monaco 383 in particular, with the "recessed mount" brake drum. "Recessed mount" means the fins wrap around to the wheel mounting point, going outside of that diameter, hence the "recessed mount" nomenclature (which can also affect which wheels can fit the drum).

As I recall, the HD Brakes 11x3 brake drums can go on all four wheels? As others use a wider drum on the front and a bit narrower on the rear. Then, some front drums are finned as the rear drums are smooth, relating again to heat dissipation and such of each axle's wheel brake system performance.

Enjoy!
CBODY67

 

[mrfury68]

Contact Craig @mobileparts. He will be able to tell you what years interchange and can sell you a quality set of drums for a reasonable price. He’s a great guy to deal with.

 

[MoPar~Man]

Uggh. I am such a dummy. I keep forgetting that my back shoes are 2" wide.

It seems that there was a transition between '68 - '69 in terms of making 2.5" rear shoes the standard.

I am going to have my rear drums checked, see if they need machining. This is one of them - seems pretty beefy, I don't know if they're the originals:

Can anyone ID these? They weigh 8 kg (17.5 lbs) but strange thing, one is about .9 lbs heavier.

I've bought some new 2.75" drums locally for the front, but I'm going to have to separate the hubs from the drums, not looking forward to that.

I've made some measurements between the new 2.75" vs these old rear 2", and I've placed the new drums on the rear axle, they don't quite seat, they'd need another 1/4". I would guess that 2.5" would actually fit, or might need a small amount of the friction ring ground away to clear the backing plate. Has anyone ever explored doing this?

 

[Just Carbs]

Uggh. I am such a dummy. I keep forgetting that my back shoes are 2" wide.

It seems that there was a transition between '68 - '69 in terms of making 2.5" rear shoes the standard.

I am going to have my rear drums checked, see if they need machining. This is one of them - seems pretty beefy, I don't know if they're the originals:

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Can anyone ID these? They weigh 8 kg (17.5 lbs) but strange thing, one is about .9 lbs heavier.

I've bought some new 2.75" drums locally for the front, but I'm going to have to separate the hubs from the drums, not looking forward to that.

I've made some measurements between the new 2.75" vs these old rear 2", and I've placed the new drums on the rear axle, they don't quite seat, they'd need another 1/4". I would guess that 2.5" would actually fit, or might need a small amount of the friction ring ground away to clear the backing plate. Has anyone ever explored doing this?

Question was.
----------------------I've made some measurements between the new 2.75" vs these old rear 2", and I've placed the new drums on the rear axle, they don't quite seat, they'd need another 1/4". I would guess that 2.5" would actually fit, or might need a small amount of the friction ring ground away to clear the backing plate. Has anyone ever explored doing this?----------------------




Yes. I use a brake lathe. Before I got the lathe, I mounted the drums backwards on the rear axle and put the car in first or reverse and ground as needed with a 4.5 angle grinder. Then put the drum on a front spindle/hub with the seal and grease removed to eliminate the resistance. This allowed me to find the heavy spot to rebalance it. The results were always good.

The inside face of the drum/axle mating surface may contact the outer metal edge of the shoe with some mix and match combos. So, it's necessary to check that and not just the overall height. That info can "usually" be found on RockAuto as described earlier in post #2.

It's common to use 72 New Yorker rear drums on the front "and" rear of the 64 New Yorker.

I've had to marry (bolt) the "NEW" 72 drums onto the 64 divorced hubs and "then" turn the new drum/hub as a unit.
Had zero success turning the drums alone without "first" mounting them to the divorced hubs. And zero success using them on the old hubs right out of the box without turning them.

Also, my experience on "checking" drums has been that it's almost necessary to give them a light cut (0.5 mm) to check them. I have mounted them on the brake lathe and checked them at a few places on the drum and they looked very close to good, but when cut, it showed that they needed to be cut.

 

[volksworld]

wouldn't trust RockAuto's listings for those brakes...they list the rear shoes as 2 1/2 except I have 2 68 Sport Fury's here and both have 2'' shoes...only my wagon uses 2 1/2

 

[CBODY67]

Several years ago, in looking for possible replacement drums for one of my C-bodies, it was confirmed that what RA has in their catalog is only as good as what the vendors have in THEIR catalogs. In some cases of name brand brake drums, the desired listings were vague, having to look in the back of the catalog for part number specs to really find out they didn't have what I needed. As if in the dreaded "combination of part numbers", they were trying to make 11x3 and 11x2.75 brakes use the same brake drum.

Which meant I either had to un-archive some old paper parts books, from vendors, or look for better listings. Which has yet to happen. Or look at brands not listed in RA.

Just some experiences and observations,
CBODY67

 

[MoPar~Man]

Yes. I use a brake lathe. Before I got the lathe, I mounted the drums backwards on the rear axle and put the car in first or reverse and ground as needed with a 4.5 angle grinder. Then put the drum on a front spindle/hub with the seal and grease removed to eliminate the resistance. This allowed me to find the heavy spot to rebalance it. The results were always good.

I almost wish that would have been my only option - to buy a set of 2.5" and grind them while turning on the car. That would have been - fun.

But, here we are. Turned, and shot-blasted (or shot-peened?):

They're 2.5% (200 grams) lighter now. The width of the friction-face is pretty much 6 cm (2.36") so these are not 2.5" drums - they are 2" drums. But they're finned, which I'm guessing would not have been typical for a slant-6 or 318 car? It's totally likely these are not the original rear drums on my '67 Monaco, if that's the case they would have been acquired back in '87. Would a pick-up or van have had 2" finned drums?

$ 113 CAD (tax-in, or $80 USD) for the blasting and turning at a local machine shop (no garages around here do this any more).

 

[MoPar~Man]

11X2 REAR BRAKE DRUMS - Sweptline.ORG

Some of that - I don't get. They're talking about full-size (C-bodies) up to '74 having 2" rear drums? Really?

But it looks like my drums really did come from a d100?

Rockauto is showing Raybestos 2955R as being "Rear, with 11in x 2in brakes" and is available ($50). Also seeing DYNAMIC FRICTION 36540007 as being 2" and is available.

BUT - they show those as application 1969 and newer. They don't list those particular (and AVAILABLE) 2" drums for anything 1968 or older. Why?

 

[cudamark]

Assuming your rear axle assembly is stock, it could have 11 X 2", 11 X 2 1/2", or 11 X 3" rear brakes. It was based mainly on engine size and the use the vehicle was made to do. Lower horsepower cars usually had the smaller brakes and high horsepower and many station wagons had the big ones, as well as most tow packages. As for interchange on the 11 X 2" brakes, they ran from 1965 to 1975 on C-bodies and '65-71 on the D100 pickups. They made both smooth and finned drums. Replace them as a set however as the heat dissipation rates were different and can cause the brakes to pull to one side once hot. To change to wider brakes would require matching backing plates and some hardware. Here's a few factory part numbers to maybe help in a search....3004746, 3780525, 2530308, 2823816, 3004932, 3549843. The reason for all the different ones were not only the fins vs non-fins, it was also the supplier. They were made by both Motor Wheel and Kelsey Hayes. Probably some superceded numbers in there too.

 

[Just Carbs]

I have a 72 New Yorker. It came to me with 2-inch rear shoes and retainer pins. I don't think it was made with 2-inch rear shoes and retainer pins. And the shoe positioning post was too long for the 2-inch shoes.
I put 2.5 shoes and pins on the rear. They fit the shoe positioning post and backing plate along with the drums that were on the car.
My guess is someone put the wrong shoes on the car. But the shoes did fit.