10 X 1.75 rear drums on 7.25 rear vs. 8 3/4

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cudavert

cudavert

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Did Mopar ever actually use the same 10 X 1 3/4" rear drum brakes on a 7 1/4" rear end as on the 8 3/4" rear end? Here's the deal.....I just yanked out my old wimpy 7 1/4" rear end and installed an 8 3/4".....I installed the correct (and all rebuilt) backing plates from an A-body. I thought I had some 10 X 1 3/4" drums laying around, but apparently I don't. So, now I'm thinking I'm officially screwed....until...

So then I look over at the 7 1/4" rear end....and start measuring.....and find that IT has 10 X 1 3/4" rear brakes on it!!! Is this some kind of option??....my '68 Dart is a GT.....and it appears to be super untouched and original, so I'm fairly sure the brakes are too.

It seems like all the other 7 1/4" rear ends I've accumulated and played with have all had 9" drums on them.....any experts or somewhat knowledgeable folk have some info??......or wish to chime in??? Would those backing plates on the 7 1/4" rear be worth anything?
 
The guts are worth something, but the backing plates aren't. I believe that the bolt pattern on those versions of 7 1/4's is different from the 8 3/4.

My '70 Duster also came with a 10x1 3/4" backing plate 7 1/4.
 
driversside.jpg
Yes I just parted out a 74 dart swinger with a 318 and it had a 7 1/4 Big bolt pattern with the larger 10" brakes . I installed it for now till I get my 8 1/4 built with a suregrip and different gears ? Used the 74 7 1/4 instead of the 69 because I swapped the front disc also with the larger bolt pattern. I wanted the front and rear to match . I had to buy new rims and tires . What a tragedy!
 
ya, the v8 cars got the 10" drums but not the flared drums like the sport models with 8.75
 
doug 371 said:
ya, the v8 cars got the 10" drums but not the flared drums like the sport models with 8.75
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When you say "sport models" do you mean like the Demon & the high performance models? Which cars actually had the flared drums? I know mine came from a Demon & it has the flared drums. Can't say for certain but I THINK it was a 340 car. I only got it a bit over 30 years ago...memory fading......
 
doug 371 said:
ya, the v8 cars got the 10" drums but not the flared drums like the sport models with 8.75
Click to expand...

WastedDays and myself stripped a 74 Valiant 4 door last summer with a 7 1/4 inch rearend. It had the 10 3/4 inch brakes with flared drums. This was a six cylinder car with Kelsey Hayes disc brakes on the front.

Previous posters are correct in that the backing plates are not compatable with the 8 3/4 rearend.
 
Yeah, I parted out a wrecked '70 Duster with a 318/3-speed and an 8 3/4" rear with flared drums......what's up with the flared drums?.....cooling? Whatever....I'm gonna run these 10" drums on the new 8 3/4" rear I just installed......I feel like doing a victory dance!!
 
'64 Cuda said:
When you say "sport models" do you mean like the Demon & the high performance models? Which cars actually had the flared drums? I know mine came from a Demon & it has the flared drums. Can't say for certain but I THINK it was a 340 car. I only got it a bit over 30 years ago...memory fading......
Click to expand...

yep...that is what i meant...
 
plumcrazy 101 said:
WastedDays and myself stripped a 74 Valiant 4 door last summer with a 7 1/4 inch rearend. It had the 10 3/4 inch brakes with flared drums. This was a six cylinder car with Kelsey Hayes disc brakes on the front.

Previous posters are correct in that the backing plates are not compatable with the 8 3/4 rearend.
Click to expand...

a 74 valiant with disc brake option would get big bolt discs...somebody probably changed some things there...
 
According to my brake source guru, the flared drums were a snowbelt drum that would keep the road slush and snow from sneaking behind the drum and into the brake assembly. He had a ton of the regular drums for 8 3/4 but none of the flared drums, which he says are not available anymore. He has tons of brake stuff for Mopars from the 30's right up through the 70's, and a lot of truck stuff too. I don't know about the snowbelt theory (he called them Canadian drums), but he sure knows Mopar brakes, and for lack of a better explanation, I'm going with it!!! Geof
 
169dart4y said:
driversside.jpg
Yes I just parted out a 74 dart swinger with a 318 and it had a 7 1/4 Big bolt pattern with the larger 10" brakes . I installed it for now till I get my 8 1/4 built with a suregrip and different gears ? Used the 74 7 1/4 instead of the 69 because I swapped the front disc also with the larger bolt pattern. I wanted the front and rear to match . I had to buy new rims and tires . What a tragedy!
Click to expand...

Yeah....what a tragedy! Man, I love the way your car looks! My '69 started out life as a copper-colored Western Sport Special!
 
plumcrazy 101 said:
WastedDays and myself stripped a 74 Valiant 4 door last summer with a 7 1/4 inch rearend. It had the 10 3/4 inch brakes with flared drums. This was a six cylinder car with Kelsey Hayes disc brakes on the front.

Previous posters are correct in that the backing plates are not compatable with the 8 3/4 rearend.
Click to expand...

doug 371 said:
a 74 valiant with disc brake option would get big bolt discs...somebody probably changed some things there...
Click to expand...

A typo on my behalf as it was a 72 Valiant
 
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