7 1/4 rear
- Thread starter dart67
- Start date
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I have a 74 Dart Sport 318 car, and the one I pulled out of it was large bolt pattern.
Measure it and see.
Measure it and see.
roadrunnerh
Well-Known Member
The bolt pattern on my 1975 /6 Scamp with 7.25 is 4.5, infact I am using the backing plates and brakes on my 8.75 Swap.
Not sure if it's the same on 74, I believe it is.
Not sure if it's the same on 74, I believe it is.
Bulldozer
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my 7 1/4 73 duster /6 with 9" drum was 4"
Didn't they all go to big bolt pattern in 73
Bulldozer
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there seems to be a lot confusion with the 73 and 74 cars. some say the V8 dictated 7 1/4 BBP in 73+ , some say the disc brakes dictated 7 1/4 BBP in 73+. i heard of 6/ cars with disc brakes and BBP and ive heard of 318 cars with SBP. my original 74,000 mile 73 6/ car with drums all the way around is a 4" pattern. i am almost positive that the disc brakes could not be had in 4" pattern, but that wouldnt explain the 8 3/4 with front disc and a 4". from all ive read the A body 8 3/4 was a 4" pattern only and later went to a 8 1/4 BBP. i am just as confused as a lot of us. maybe someone can clarify this. im sure this has been brought up a dozen times. and..i dont think the A body 8 1/4 came with a 4" pattern. there needs to be a sticky chart outlining all A body rear ends, with their production runs and pattern sizes, along with a disc/drum breakdown of years and 4 to 4 1/2 pattern usage, and what dictated what.
I had a 73 Swinger with Big Bolt Pattern 4 wheel drums...
I think maybe what happened is in 73-74 they made the change over to the larger bolt pattern. If there is a pish posh mix late 73 or in 74 it may be due to the fact they wanted to use up what they had on hand.
Just my thoughts.
Bulldozer
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to even further confuse things lol
Bulldozer
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i can believe that for sure. ive also heard of the 4" being used up to as late as 75 on A bodies before the F body took over. maybe we can get Slantsixdan over here to clarify some of this.
Not unless someone installed a BBP set up on the car.
Drum brake A bodies were SBP. Jan 1, 1976 ALL cars were disc brake, thus LBP.
73 V8 cars got Disc as Std equipment, /6 cars it was an option until Jan 1, 1976.
8.25 = BBP 7.25 could be either SBP or BBP
Bulldozer
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can pre 76 disc brake cars have SBP ?
After thinking about this you are 100% correct. I actually swapped to discs on the front of this car and remember I used some Magnum 500's that were off my B body at the time. This was almost 15 years ago now so my 73 DID NOT have BBP drums.. My bad! Oh how the memory fades lol
72 down disc cars are sbp
Bulldozer
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ok so,
pre 73 disc are 4"
73 and up disc are 4 1/2
all drum through 75 are 4"
im just making sure i got this straight.
did the 8.25 replace the 8.75 in 1973?
pre 73 disc are 4"
73 and up disc are 4 1/2
all drum through 75 are 4"
im just making sure i got this straight.
did the 8.25 replace the 8.75 in 1973?
Yes on 8.25 replacing 8.75 in 1973.
SBP drums were available until mid year 1976 models.
SBP drums were available until mid year 1976 models.
Bulldozer
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and obviously the 7 1/4 ran for many years. thanks crackedback great clarification. so the 7 1/4 was used for V8 and /6 applications i assume? any idea as to what dictated an 825 to a 725 in post 73. would the 825 been for 340/360 applications in 73 and up cars and the 725 in 6/ and 318 cars?
340/360 got the 8.25 as you mention
tow package would get the larger rear in a 318 or /6.
tow package would get the larger rear in a 318 or /6.
cudamark
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e50095
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Just one more point on this as an FYI.....the small bolt pattern 7 1/4 rears cannot be switched to large bolt pattern just by changing the axles to a pair from a large bolt pattern 7 1/4. I can't remember why off the top of my head.....I believe the innerds are different somehow...
Bulldozer
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i was told the BBP axles are bigger in diameter and that if the bearings are changed, that you can use them. but i dont know from experience, maybe someone can elaborate. and im glad you added that info here.
caferacerx
BAND MEMBER
BBP drums are wider than SBP drums so the 7-1/4 rear housing is narrower to accommodate the wider drums
the easy way to remember BBP from SBP disk brakes is
single piston = big bolt
four piston = small bolt
8-1/4 rear = big bolt
8-3/4 rear = small bolt
all front drum brakes = small bolt
7-1/4 rear both SBP and BBP
the easy way to remember BBP from SBP disk brakes is
single piston = big bolt
four piston = small bolt
8-1/4 rear = big bolt
8-3/4 rear = small bolt
all front drum brakes = small bolt
7-1/4 rear both SBP and BBP
cudamark
Well-Known Member
Bearing size and axle shaft length.
C130 Chief
Mechanical Genius
The width difference was only on 9" drum rears. 9" drums only came on 7 1/4" rears and all were SBP
cudamark
Well-Known Member
I'm not sure exactly what you're trying to say about this. The 7 1/4 axle shafts with the SBP all interchange from '63-76. The 7 1/4 axle shafts with the BBP all interchange from '73-6. The problem is when you try to put a BBP axle shaft into a SBP housing. They won't fit because of the bearing size and length of the axle shaft.
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