Trying to figure out what I have

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Jeremiah David

Jeremiah David

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I have a 73 Duster and looking up it should have came with an 8 3/4 but the dif cover does not match. I'm guessing it's a 8 1/4 just from the dif cover, but I'm not exactly car savy.

The tag on it says 3.21, the cover is not perfectly round like a 8 3/4 is. If somebody could give a little insight it would be much appreciated.

IMG_20170906_135635.jpg
 
8 1/4. 8 3/4 doesn't have a cover it drops on the front as an assembly. (the assembly is called a 3rd member)

8.75moparrearend.jpg
 
that is an 8-1/4 rear and the gear ratio is 3.21....There was no 8-3/4 rear from the factory in a 1973 car....1972 was the last year for the 8-3/4 rear.......That is a good rear you have and that is what they put behind the 340 cars in 1973 with the same 3.21 ratio
 
bbrroowwnn said:
that is an 8-1/4 rear and the gear ratio is 3.21....There was no 8-3/4 rear from the factory in a 1973 car....1972 was the last year for the 8-3/4 rear.......That is a good rear you have and that is what they put behind the 340 cars in 1973 with the same 3.21 ratio
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So this would have came stock with a 340 then? I was trying to figure out what was stock in it before the engine swap as I got the car with it changed. It now has a rebuilt 360 in it, with a Holley 3310 750 cfm carb.
 
in 1973 the a body switched to the 8 1/4". there is a mini spool-not for the street. u want some form of sure grip carrier, see what is available?
 
Jeremiah David said:
So this would have came stock with a 340 then? I was trying to figure out what was stock in it before the engine swap as I got the car with it changed. It now has a rebuilt 360 in it, with a Holley 3310 750 cfm carb.
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Yes 340 , or it also could have been an optional upgrade from a 7-1/4 rear on a 318 or slant six car.....The easiest way is locate your broadcast sheet to see what your car had in it originally....usually under the rear seat in under the seat springs.....To see if your car was a 340 car or not just look at the 5th digit of your VIN number....if it is the letter H it had a 340 in it from the factory......If it is a letter G it was a 318....a letter C there would indicate a slant six car.....
 
bbrroowwnn said:
Yes 340 , or it also could have been an optional upgrade from a 7-1/4 rear on a 318 or slant six car.....The easiest way is locate your broadcast sheet to see what your car had in it originally....usually under the rear seat in under the seat springs.....To see if your car was a 340 car or not just look at the 5th digit of your VIN number....if it is the letter H it had a 340 in it from the factory......If it is a letter G it was a 318....a letter C there would indicate a slant six car.....
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So with that info it had a slant 6
 
Also a factory 8-1/4 rear in an A body means front disc brakes.
 
On your broadcast sheet, if you find it....D82 was the code for a 8.25 rear and D53 was the code for 3.21:1 gear ratio in it
 
I didn't see where anyone asked about a fender tag. It's a 3" long metal tag screwed onto the drivers fender. Lots of info stamped onto that tag.
 
toolmanmike said:
I didn't see where anyone asked about a fender tag. It's a 3" long metal tag screwed onto the drivers fender. Lots of info stamped onto that tag.
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yes, lots of info but not axle...have to go to broadcast sheet for that
 
bbrroowwnn said:
yes, lots of info but not axle...have to go to broadcast sheet for that
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Sorry I asked. The owner seems to want to know about his car and doesn't know much about it or where to look.
 
If it originally was a slant six car like you said it was by the 5th digit of VIN being the letter C chances are it probably came with a 7-1/4 axle from the factory....I highly doubt it was optioned up to the 8-1/4 rear....especially with 3.21 gears....Chances are that was put in when the 360 was put in...
 
toolmanmike said:
Sorry I asked. The owner seems to want to know about his car and doesn't know much about it or where to look.
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No, don't be sorry Mike....lots of good info on fender tag....sorry if I came off like a butthole.....didn't mean to.....
 
i bought a 74 duster 225 6cylinder, came with an 8 1/4 ,321 gear from factory
 
Sounds like a basic /6 to V8 swap with a rear end upgrade done by a previous owner.
Not a bad thing, as we all should have been lucky enough to have an 8.25 when we got our cars stock.
 
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