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8 3/4 rear end swap from 7 1/4
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Author:  Mopar Madness [ Thu Sep 12, 2002 6:35 pm ]
Post subject:  8 3/4 rear end swap from 7 1/4

I have a 72 duster with a bit of a hopped up six in it, cam, header, 2bbl, head work, block 0.030" over etc . Anyways my 7 1/4 rear end isn't taking it too well it's starting to go. I was just wondering if I got an 8 3/4 rear end from an A-body it would have the small bolt battern right? and if I could bolt the 9 inch drums and backing plates onto the 8 3/4 rear end? Any pointers for doing this conversion would be great

craig_o_connor88@hotmail.com

Author:  Patrick Devlin [ Thu Sep 12, 2002 8:56 pm ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

When I changed my Dart's rear to the 8 3/4 from the 7 1/4 this summer, I tried to use the 9" drum backing plates and drums. And guess what? Despite what I've read on the 'net, it doesn't work. Drilling the fifth backing plate hole is not the only problem. You'd have to drill out the center of the plate to get the larger axle bearing of the 8.75 through.

AND, once you have all of this done, the offset of the axle flange to the backing plate will be incorrect, so the drums won't fit correctly.

So, my suggestion is that you find some 10"x 1.75" drums, backing plates, hardware, etc. I had to do this because I wanted to keep my small bolt wheels. If you're not attached to your wheels, you might find it easier to get some large bolt axles for the rear so that you can use the B-body drums, etc. which are easier to find.

That's my longest reply ever!
Quote:
:
: I have a 72 duster with a bit of a hopped up
: six in it, cam, header, 2bbl, head work,
: block 0.030" over etc . Anyways my 7
: 1/4 rear end isn't taking it too well it's
: starting to go. I was just wondering if I
: got an 8 3/4 rear end from an A-body it
: would have the small bolt battern right? and
: if I could bolt the 9 inch drums and backing
: plates onto the 8 3/4 rear end? Any pointers
: for doing this conversion would be great



pwd22@drexel.edu

Author:  dschumers [ Thu Sep 12, 2002 9:04 pm ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

Yep, 9" brakes won't work. Parts are still available for the 10"X1-3/4" though, and the car will stop much better. The driveshaft will need to be shortened 1-3/4" too. Dennis

slantzilla@excite.com

Author:  Doctor Dodge (Doug Dutra) [ Thu Sep 12, 2002 9:20 pm ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

Quote:
: When I changed my Dart's rear to the 8 3/4 from
: the 7 1/4 this summer, I tried to use the
: 9" drum backing plates and drums. And
: guess what? Despite what I've read on the
: 'net, it doesn't work. Drilling the fifth
: backing plate hole is not the only problem.
: You'd have to drill out the center of the
: plate to get the larger axle bearing of the
: 8.75 through.
:
: AND, once you have all of this done, the offset
: of the axle flange to the backing plate will
: be incorrect, so the drums won't fit
: correctly.
:
: So, my suggestion is that you find some
: 10"x 1.75" drums, backing plates,
: hardware, etc. I had to do this because I
: wanted to keep my small bolt wheels. If
: you're not attached to your wheels, you
: might find it easier to get some large bolt
: axles for the rear so that you can use the
: B-body drums, etc. which are easier to find.
:
: That's my longest reply ever!


Great reply! Good to hear from people who have actually done the swap.

Besides *not* being able to use the 9 inch brakes, also be sure to get the shock plates and "U" bolts for the 8 3/4, these are bigger.
The emergancy brake cables come in many different sizes so take a close look at those and swap over the ones from the 7 1/4 if there is any differences.
The driveshaft will need to be shorter, best to get the new rear-end installed and thaen take an accurate measurement with the car at normal ride height. (appx 2 inches shorter is the general "rule")
8 3/4s are great units, it's well worth the effort to swap over.
DD

Author:  Dart270 [ Fri Sep 13, 2002 5:36 am ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

Quote:
: Yep, 9" brakes won't work. Parts are still
: available for the 10"X1-3/4"
: though, and the car will stop much better.
: The driveshaft will need to be shortened
: 1-3/4" too. Dennis


Just to be clear. All A-body 8.75" axles had small bolt (4") pattern from the factory, and the 10 X 1.75" brakes. To the best of my knowledge anyway...

Lou

Author:  Charlie Schmid [ Fri Sep 13, 2002 8:05 am ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

Quote:
: Great reply! Good to hear from people who have
: actually done the swap.
:
: Besides *not* being able to use the 9 inch
: brakes, also be sure to get the shock plates
: and "U" bolts for the 8 3/4, these
: are bigger.
: The emergancy brake cables come in many
: different sizes so take a close look at
: those and swap over the ones from the 7 1/4
: if there is any differences.
: The driveshaft will need to be shorter, best to
: get the new rear-end installed and thaen
: take an accurate measurement with the car at
: normal ride height. (appx 2 inches shorter
: is the general "rule")
: 8 3/4s are great units, it's well worth the
: effort to swap over.
: DD


I am doing the 7 1/4 to 8 3/4 swap now, on my 66 Cuda. How ever since I have a 65 trans, it is a little more involved. Had to have a new drive shaft made, since I have the ball and trunion front joint. Had a drive shaft shop fab a shaft, that uses a flange and standard u-joints and slip yoke.

flturbo6@aol.com

Author:  John Killin [ Fri Sep 13, 2002 8:29 am ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

Charlie,

Can you give more details on your drive shaft modifications?

I am planning to do a rear end swap on my 63 Valiant.

Did they modify an existing shaft, or make a new one? Cost?

Thanks,

John
Quote:
: I am doing the 7 1/4 to 8 3/4 swap now, on my
: 66 Cuda. How ever since I have a 65 trans,
: it is a little more involved. Had to have a
: new drive shaft made, since I have the ball
: and trunion front joint. Had a drive shaft
: shop fab a shaft, that uses a flange and
: standard u-joints and slip yoke.



Killin5@yahoo.com

Author:  kesteb [ Fri Sep 13, 2002 1:15 pm ]
Post subject:  Re: 8 3/4 rear end swap from 7 1/4

Quote:
: Charlie,
:
: Can you give more details on your drive shaft
: modifications?
:
: I am planning to do a rear end swap on my 63
: Valiant.
:
: Did they modify an existing shaft, or make a
: new one? Cost?


I had the driveshaft in my '65 shortened when I went to the 8.25" axles.


klesteb@aol.com

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