7 1/4 to 8 3/4 rear end swap

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gotdust57@yahoo

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i have a 73 duster with 318 and 727 trans and would like to change the rear end from 7 1/4 to something bigger like 8 3/4 or 8 1/4 i have never done this before but sure i can, what would i need to complete swap other then rear end, and would 8 1/4 be better than 8 3/4 this is for street use only just affraid the 7 1/4 in it is to small? thanks for any help
 
It's a relatively easy job. The E-brake cable is a mother%&*er sometimes but you can do it in an afternoon. The only thing that might be a problem is your driveshaft U-joints. the 7 1\4 had the small yoke and the 8 3\4-8 1\4 had the bigger yokes. You'll have to get your driveshaft cut down so they can add the new yoke when they do it.
 
Not all 8-3/4 rears had bigger U-joints. Mine don't. I haven't seen many but from what I've read all A-body rears have the small U-joints. Also have a good look at the rubber brake line leading from the body to the rear. If it's original chances are it's cracked and worn pretty bad. Now would be a good time to replace it.

With your 318 the 8-1/4 would do you just fine and be alot cheaper than a 8-3/4. The 8-3/4 rears are bringing a premium these days.
 
Yea, my u-joints are the small ones because when i swapped the case outta the challenger to put in my cuda, i got the one bolted up in the challenger and the drive shaft wouldnt fit. dave
 
Yep, gotta go with the 8 1/4 for the street. There are plenty of parts and ratio's available for it should you decide to go through it. I've actually seen them survive abuse that many said was reserved for it's bigger brothers.

Revhendo

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thanks all for your help and are you saying with 8 1/4 my small yoke and u joints will work just fine
 
It's possible but you'll need to measure to make sure because even the 8-1/4 came both ways, i.e. big and small U-joints. I was just saying all the factory A-body rears I saw had the small U-joints. Problem is someone along the line could have changed the yoke.
 
I think you`ll find the large u-joint (7290) on the 340 and 383 cars, mine have always had the large joint with those engines. They do make a universal that has a 7260 on one side and a 7290 on the other.
 
something else to think about is if the new rear end is giong to be able to fit right in place without any major modifications. I am doing the same thing with my duster, taking out the 7 1/4 and putting in an 8 3/4, i am getting the new rear end out of an old dart, so i wont have to do much modifing, also, my new rear end has the same bolt pattern as the 7 1/4,so i wont have to go buy new wheels, thats another thing to think about---bolt pattern
 
You will still have to shorten your driveline if you swap to either the 8 1/4 or 8 3/4 or get the driveline out of the car you are getting the rearend out of.

To use the 8 1/4 you have to shorten your driveline 1.5"
To use the 8 3/4 you have to shorten your driveline 2.25"
 
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