76 breaks problem

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don't suppose you happened to measure the axle tube diameter or width between the U-bolts. a 7.25" will be 2.5"....I think that looks like a 7.25, but the tag stumps me, I've only seen 2.24, 2.45, 2.76, 2.94, 3.23, 3.55, 3.91, and 4.10 as typical axle ratios from '60's-80's mopars, and the tag usually is 1 line with just the ratio. that tag looks more like a tag you'd see on a ford axle....

what bolt pattern is it again? you didn't happen to measure the center register of the axle? Fords are 2.75", mopar ~2.85"
 
let's go back to "anything can happen in 40yrs" and think about the possibility that this might not be an a-body axle or even a mopar piece...

granted, i haven't looked at any other diff cover patterns. and 9 bolts certainly points to 7.25 but have you confirmed that there's a chry co stamp on it somewhere?

also, can you pull a PN off the backing plate? i suppose there's a remote possibility that somebody did an ol switch-a-roo at somepoint because of cost, availability or they were a cheap *** and that's what they had sitting around.
 
michiganpat said:
don't suppose you happened to measure the axle tube diameter or width between the U-bolts. a 7.25" will be 2.5"....I think that looks like a 7.25, but the tag stumps me, I've only seen 2.24, 2.45, 2.76, 2.94, 3.23, 3.55, 3.91, and 4.10 as typical axle ratios from '60's-80's mopars, and the tag usually is 1 line with just the ratio. that tag looks more like a tag you'd see on a ford axle....

what bolt pattern is it again? you didn't happen to measure the center register of the axle? Fords are 2.75", mopar ~2.85"
Click to expand...
I did not measure the diameter. I will be going back to the shop on Thursday i can measure it then.
Bolt patter i believe we discovered to be 5 × 4.5"
Does this picture help with the center of the axle?

20240328_121818.jpg


20240328_121823.jpg
 
junkyardhero said:
let's go back to "anything can happen in 40yrs" and think about the possibility that this might not be an a-body axle or even a mopar piece...

granted, i haven't looked at any other diff cover patterns. and 9 bolts certainly points to 7.25 but have you confirmed that there's a chry co stamp on it somewhere?

also, can you pull a PN off the backing plate? i suppose there's a remote possibility that somebody did an ol switch-a-roo at somepoint because of cost, availability or they were a cheap *** and that's what they had sitting around.
Click to expand...
I havent seen any chry co anywhere on the axle. I can try to get and get a PN but if you look back at one of dana67dart replies he posted a picture of a 67-68 backing plate and it matches basically perfectly.
 
This is just a partial image of the chart in my post above.

But only the 7 1/4 lists 9 cover bolts.

Screenshot_20240402-180957.png
 
slant6dart76 said:
I havent seen any chry co anywhere on the axle. I can try to get and get a PN but if you look back at one of dana67dart replies he posted a picture of a 67-68 backing plate and it matches basically perfectly
Click to expand...
it should be something that's dead simple. it's BBP 7.25 (are you sure it's 5X4.5 pattern) so it should be a slam dunk. even if rock sent the wrong parts, or the wrong stuff is on there all the right junk exists out there.

it might be pain, but the path forward could be just rolling to the local parts store with parts in hand and playing the match game.
 
Im
Dana67Dart said:
I have a theory...

The backing plates are 68 and older B,C body 10x2.5?
The hardware and the backing plates match pre 69 parts
The rear seems to be a 76 7 1/4 with 1/2 inch studs, 5x4.5 bolt pattern and the large center register.

Dr Frankenstein would be proud

Evidence...

Car is a 76 /6 which got 7 1/4 but with BBP
Mechanic states the old shoes are 10x1.75 simple measurement. A lot of difference between 1.75 and 2.5 I doubt he mis-measured


67-68 10x1.75 backing plate
View attachment 1716228610

OPs backing plate
View attachment 1716228611

69 - 76 Automatic adjuster cable
View attachment 1716228613


OPs automatic adjuster cable (pre 69)

View attachment 1716228612



10x1.75 69 up backing plate, the spacing is tiny
View attachment 1716228615




OPs backing plate, the spacing is huge compared to 1.75, easily 3/4 of an inch more

View attachment 1716228614


So my theory...

The backing plates MIGHT be correct for 10x2.5 brakes only a test fit or some measurements will know for sure.
The backing plates and hardware came off a 68 and older rear
Somewhere along the way someone put 10x1.75 shoes on (how they fit is a mystery to me, The shoes being narrower would not interfere so in theory it could work)


I believe the OP needs to go to a local auto parts store and buy 10x2.5 rear drums for a 76 Dart /6 rather then ordering them. Taking the old drum that fits the hub and the studs and the backing plate along for size.

This can also be done to determine what drum the backing plate fit

View attachment 1716228638

View attachment 1716228637

View attachment 1716228636
Click to expand...
I'm going to try and fit the 10" by 2.5 on and see how they fit. I will update you
 
junkyardhero said:
it should be something that's dead simple. it's BBP 7.25 (are you sure it's 5X4.5 pattern) so it should be a slam dunk. even if rock sent the wrong parts, or the wrong stuff is on there all the right junk exists out there.

it might be pain, but the path forward could be just rolling to the local parts store with parts in hand and playing the match game.
Click to expand...
Went to local parts store and they dont have anything in their system that would match the:
5x4.5
10" diameter
1 3/4 depth
I just comfirmed the large pattern. As far as I am aware the front disks only came in int 4.5 (big pattern) i tried my wheels and they fit both front and back, thus big pattern in the back as well. Let me know if I'm wrong.
 
michiganpat said:
don't suppose you happened to measure the axle tube diameter or width between the U-bolts. a 7.25" will be 2.5"....I think that looks like a 7.25, but the tag stumps me, I've only seen 2.24, 2.45, 2.76, 2.94, 3.23, 3.55, 3.91, and 4.10 as typical axle ratios from '60's-80's mopars, and the tag usually is 1 line with just the ratio. that tag looks more like a tag you'd see on a ford axle....

what bolt pattern is it again? you didn't happen to measure the center register of the axle? Fords are 2.75", mopar ~2.85"
Click to expand...
I was only able to get the CIRCUMFERENCE of the axle which was 8"
 
Last edited:
slant6dart76 said:
Went to local parts store and they dont have anything in their system that would match the:
5x4.5
10" diameter
1 3/4 depth
I just comfirmed the large pattern. As far as I am aware the front disks only came in int 4.5 (big pattern) i tried my wheels and they fit both front and back, thus big pattern in the back as well. Let me know if I'm wrong.
Click to expand...
according to my '76 factory service manual, disc brake cars only came with 10x2.5" rear drums. 10" drum brake cars (what mine was, with a 11/75 build date) come with 9" rear drums and small bolt pattern. '73 up I've only seen 10x2.5" listed as the rear drums on BBP A bodies. heck, looking on rockauto I can't find ANY 10x1.75" rear brake applications in mopars going back to '64....

here's a drum for a 10x1.75", application is a 1970 AMC hornet with disc brake fronts.....might be worth a shot?
More Information for FVP 12367024
 
michiganpat said:
according to my '76 factory service manual, disc brake cars only came with 10x2.5" rear drums. 10" drum brake cars (what mine was, with a 11/75 build date) come with 9" rear drums and small bolt pattern. '73 up I've only seen 10x2.5" listed as the rear drums on BBP A bodies. heck, looking on rockauto I can't find ANY 10x1.75" rear brake applications in mopars going back to '64....

here's a drum for a 10x1.75", application is a 1970 AMC hornet with disc brake fronts.....might be worth a shot?
More Information for FVP 12367024
Click to expand...
Is it possible that someone threw those 10" 1 3/4 in and they just happened to fit?
The backing plate seems to match the 68 to 70 one @Dana67Dart posted
 
i *think* i know what may have happened... need to investamagte a little more and review the pics to verify.

but i think somewhere along the line the brakes OR the axle got a switch-a-roo-- like an early axle housing with brakes got put in and they switched the axles shafts and drums out to BBP, or early backing plates and shoes got put on that housing.
 
slant6dart76 said:
Thanks the shoes I have, the problem is the drums.
Click to expand...
i think part of the issue is stemming from the variance in nomenclature and colloquial descriptions regarding brakes.

for instance, a 72 8 3/4 uses a 10x2 drum, but the shoes are 1.75 and a 7.25 that uses 9" brakes would measure 9x2.25 and take a 2" shoe (technically the friction surface of the drum is listed as 2.33, but close enough).

so if you have 1.75" shoes, you need a drum that has a 2" friction surface

clear as mud, no?
 
slant6dart76 said:
Went to local parts store and they dont have anything in their system that would match the:
5x4.5
10" diameter
1 3/4 depth
Click to expand...
65 thru 68 mustang has 10x1.75 AND 5x4.5

A number of manufacturers used Bendix for their brakes so the interchangability is posable
 
junkyardhero said:
i think part of the issue is stemming from the variance in nomenclature and colloquial descriptions regarding brakes.

for instance, a 72 8 3/4 uses a 10x2 drum, but the shoes are 1.75 and a 7.25 that uses 9" brakes would measure 9x2.25 and take a 2" shoe (technically the friction surface of the drum is listed as 2.33, but close enough).

so if you have 1.75" shoes, you need a drum that has a 2" friction surface

clear as mud, no?
Click to expand...
Couldn't have said it better.
Click to expand...
 
If I'm not mistaken, that little 'ramp' around the center hole on those drums is going to cause a problem when you bolt those wheels on. That surface needs to be flat.
 
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