71 Dart 7 1/4 to 8 3/4 Questions

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dylan_becker

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I recently put a 360 in my 71 dart. I'm puting an a-body 8 3/4 with 4" bolt pattern in it to replace the stock 7 1/4. I'm quite the novice when it comes to rearends. I'm just wondering what snags I'm gonna hit on this swap. Will the brakes swap over? Backing plates? Any info. is greatly appreciated.
 
Youll need the shock/u bolt mounting plates for the 8.75 (the 7.25 has smaller tubes) you'll also need to have the drive shaft shortened.
 
The backing plates also do not swap over. They are the same for 8 1/4 and 8 3/4, but 7 1/4 is smaller. I believe the brake shoes and hardware will swap over if you have 10" drums on the rear. If you have 9" drums on the rear, they definitively will not. If I'm wrong about this someone will chime in quickly.....we're good about that on this forum. Good luck with your swap. One last thing....the emergency brake cables are a definitive swap over...no problems there...
 
e50095 said:
The backing plates also do not swap over. They are the same for 8 1/4 and 8 3/4, but 7 1/4 is smaller. I believe the brake shoes and hardware will swap over if you have 10" drums on the rear. If you have 9" drums on the rear, they definitively will not. If I'm wrong about this someone will chime in quickly.....we're good about that on this forum. Good luck with your swap. One last thing....the emergency brake cables are a definitive swap over...no problems there...
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Is there a place to get aftermarket backing plates?
 
I'm not aware of anyone that is making reproduction ones, but that shouldn't really be necessary. They are not a wear part, so old ones are fine and can be made to look new with a little sanding and paint. If you post an add in the parts wanted section, I'm sure there are a lot of folks that can help you out. A lot of people with 10" drums on the rear remove their backing plates when they upgrade to the larger bolt pattern as a function of converting to disk brakes. Some move up to 11" rear drums off of a van or big car, and others go with the rear disk setup off of a Jeep Grand Cherokee. Neither of these moves can be done if you're keeping the small bolt pattern, which I assume your car has. I think you'll be able to get the backing plates you need for somewhere in the $30 range. There area a lot of guys on this site that are more than happy to help and provide parts to support other folks projects on the cheap. Let me know if you need any other info...
 
I'm right in the middle of the same swap; I went with 10"x2 1/2" drum brakes that came out of a 70 Challenger. The 340 Dusters originally came with 1 3/4" wide brakes, the 2 1/2" brakes from any E or B body will fit (10" / 8 3/4 rear end). Had to get new (longer - 28") axles but was switching to BBP anyway so not a problem.
 
Dusterdenovo said:
I'm right in the middle of the same swap; I went with 10"x2 1/2" drum brakes that came out of a 70 Challenger. The 340 Dusters originally came with 1 3/4" wide brakes, the 2 1/2" brakes from any E or B body will fit (10" / 8 3/4 rear end). Had to get new (longer - 28") axles but was switching to BBP anyway so not a problem.
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This information won't help the op, he is staying with the 4 inch bolt pattern according to the original post.
 
Just letting him know that he has the option to go with an easy upgrade since he doesn't have his backing plates yet.
 
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